(less than 65
spot. Use
storage.
well. The reason is
measures
Func ()
r in Sum2 and
not alias anything by using
c + b + a;
conditions in a
take advantage
statement occupies
int BigArray[1024]; // Windows
software programmers to some of
-a >
to calculate the value of
appendix at www.agner.org/optimize/cppexamples.zip for how
appropriate here. It reveals a
has a particular
position-independent, makes a
often more
afterwards.
value 0
n; #if defined(__unix__) || defined(__GNUC__)
- x-xx----x x-xxxxxx- x-xxxx-x-
and only if the program
is a very useful way
Library. The
Conversion from floating point
or 32 bytes).
information can be left
143 if (u.i
9.6
example, if we
<< and | operations than
of an object It is
---xx---x
splitting
simply predicted to go
the entire
Nevertheless,
1)sign 2exponent 1023
can calculate a vector
always true/false Loopunrolling
constants, array
chains can be very
issue, as you can read
model and then
needs
is typically loaded at a
14.15a
Explain
important. An important
of n!
is the case then
Pointers, references,
specific order but are
given in advance. The disadvantages
numbers:
Increment
variables.
advance which of
16 bits of the 32-bit
modify
many different cases for
use single precision
for the link pointers and
history,
&& to &
good for the
objects declared
1.fffff, where
e.g. Intel
set:
use #if instead of if.
defined. The cost of
object of a class,
check the order of
146 14.12 Position-independent code..................................................................................
to test this
reference
It is recommended to make
connections
are inlined so that
SelectAddMul_AVX2, SelectAddMul_dispatch; //
internally as (int)&matrix[0][0]
the shared object, then
sizeof(float)).
type conversion generates
pointers, and
data caching less efficient.
for holding the pointer.
has three conditions
functions have names that
current array element. Rather than
simultaneously. This processor has four
individual
2004.
floating point to integer.
return
Open source.
leaks. It
a program. The
processor appears on
analyze all
a cache is
advised
way:
SVML and LIBM
T & operator[]
by a single &
spent in the program
is inefficient because
to the critical stride,
and executables.
16.2 above,
that you should look at
after executing a critical
a vector goes
a short vector library, you
cores
real-time
single precision variables in the
vector size then add
superior
roll out a big loop
pow(x,n) As we
spent in
= 1.23456,
nagging
constants.
tools,
make the induction variable
is split between several execution
Gnu compiler mechanism because
so-called symbol
be vectorized if the
affinity
is definitely the preferred
optimizing compiler can see
integer parameters
data sequentially
have AND'ed b with
optimal.
that work on all
Example 12.9b. Taylor
much space in
economy,
to x?" or "how many
have been lost at
considerably.
loop counter.
Good
against overflow is
only 64-bit execution
memory page size (4096).
of the code and
compiler inserts extra
typically uses
double precision or eight
function for register storage. The
not,
(byte
0);
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necessary to do experiments in
a reduced number of
in the same time that
a[0],
register state. This penalty should
used. Dynamic
divisions can be
later in the
is acceptable.
There is an even
OneOrTwo5[b
chapter. Using
avoided by replacing an
regardless of scope or namespaces.
follow
time-
vector, bits Vector
start and stop the
...............................................................................................
interpreter for
Use macro as inline function
for register variables are
performance during the
take advantage of this
taken into account when choosing
Arrays An array is implemented
for speed-critical functions by using
so-called
contrary, each thread may
PathScale compilers. Intel C++ compiler
beware of the pitfalls here:
8.8b double x, y;
Func 87 used cache line
but unfortunately there is no
^=
int level =
files or accessing
Dependency chains Modern microprocessors can
(0);
// Example 7.43a. Runtime polymorphism
lines follow the
using &
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on an interpreter
want to check whether
~a&~b=~(a|b) --xxxx--- a &
toggle
very few restrictions on alignment
reliable and reproducible
another array. The
a specific CPU model and
advantage in using the larger
a lot of CPU
that it fits
so that the if condition
and Windows 3.x. These
giving it some heavy
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a/1=a xxxxxxxxx
depends on the processor.
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reorganized in
x *= x; n >>=
processors).
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by the requirements of
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also be used with
more iterations
space for the parameters
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when swapping
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independent of the loop
The compiler sometimes uses 32-bit
= x2*x2;
runtime
needed before
it is not optimal to
Strings Text strings typically have
complete code
pointer aliasing is to
a loop count
illustrated by
Example 7.45 // Portability
likelihood that certain parts
Define
Unix-like platforms.
The simplest case is a
example using Agner's
does not solve all the
is faster than
examples on page
calculate
if the list
or class
(called
time, but expensive
working software users. In some
overlap the call and return
reasons:
int unsigned
128.
0/a
reasonable solution is
written.
microprocessors is split
get reliable
others are
to assembly:
Example 14.15b if (a
well, others are not. Supports
>= 11) { //
In fact,
int a[1000]; float b[1000];
__restrict
another source
73 Without optimization, the
93.
table lookup operations slow down
on the stack. A static
Example 8.11b int SomeFunction (int
algebraic reductions explicitly in
takes typically 0 -
24, 120, 720,
be fast in
the grandparent class: class
not overlap or if they
audio
define matrix
quite certain
label
a typical software
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hand-held devices are becoming
Neither is it unusual that
// x^n // sum, initialize
code because of a change
scheduler. This can
than loops, etc.
Intel/x86-compatible
are four kinds of
55 In
intended
There are intrinsic instructions for
long delay. See
function opens a file
handle its own block
modulo calculations: //
maintenance There
of identifier names.
SSE3 horizontal
to the modulo operator
x64 141
only 2-3 clock
{ if (i % 2
same space
in C++ so you need
nmmintrin.h
a common programming error. The
__restrict__,
64-bit CPUs and operating systems.
clock cycles later
handling.
optimally.
test in
itself
public: int c; }; Replace
unlimited
address plus
languages. www.yeppp.info
complex, that there
well optimized software
int)(i
below.
a switch in your
conversion from float or double
= {1.0f, 2.5f};
execution core of modern microprocessors
page 107). The
in array ;
core. Unfortunately,
area
only run
// Portability note: This example
makers assume that floating point
its variables
condition clause. Comparing an integer
fast that what is brand
(u.i * 2 >
bear
number of elements to store
cannot do must be done
we can help the compiler
0x3FFF unsigned
Instrumentation:
16.2
parameter. In other words, you
with
just-in-time compilation may be a
have to set the
enum,
high and decreased
a-(-b)=a+b a-a =
uses
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bit are
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of the program that runs
number (e.g.
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happy to receive
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sure everything that is
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below. Devirtualization
functions are optimized well, others
0.22
to ignore
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instead of a macro. If
string[100],
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recommended that
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function or otherwise optimize
geometry
1000.
mitigated
microprocessor can execute the
aware that there is often
slower,
used and searching for vacant
Mac operating system running in
are various function libraries for
64 MMX int
that the background
fraction 2 23
standard user
the storage order is opposite).
address of the variable
that make up
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of occupying a
works,
so expensive
An array using
to use the same memory
we don't need
cache cannot
significant effect on older
on Pentium
metaprogramming, but this
or graphics accelerator
higher level of optimization
the same regardless of precision
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software can
1; You cannot
data", where
have been tested only
microprocessor can predict the loop
9.4
15.1c,
QueryPerformanceCounter functions for millisecond resolution.
will make all dynamic libraries
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iteration.
Two threads running
multi-core CPUs, as described
DWORD
more
On many
at an arbitrary
a software module for correctness
< SIZE; r1 +=
the integer in the
much faster. There
operation is performed on multiple
service routines
renamed instances of
i, a[100], temp;
defining
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needs them.
reduced to: // Example
11.2b was an odd number
perfectly on a Pentium
116 // Set
is large then it
dummy[4]; volatile int DontSkip;
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so that only
Agner's vector class library can
4 256 AVX2
the dispatch on every call
highest instruction
counter ahead
at random times and make
Open files
much space in the
AVX-512
the syntax is fully standardized
8.24
and attempts
Can be reduced to:
compilers use the software implementation
const & a, T const
141
OneOrTwo5[b!=0]
Linear
The two summation
prediction. A Pentium
multiple threads must be declared
Use large
obscure possibility of overflow.
non-polymorphic
>= (unsigned
||, ! and the corresponding
to 99
utilizing
Not optimized
the bit
operators. Make a C++
bitwise
CPU cores. A process
the error code may
expressed as an 8-bit
bottleneck.
complete
slow down a program
Remember, therefore, always
by replacing an integer variable
function. This will
& 0x7FFFFF)
test situations to avoid that
for the same resources.
frame function,
in a separate module,
149
pieces of a suitable duration.
rather than dynamic linking are:
is easier to write 2.0/3.0
used for temporary storage.
by checking
CPU core). The counters will
mentioned below.
is compiling.
vector or the loop unroll
using exception handling then
declaration "static" or
<= n <
do manually. It
traffic and a
use a console
64-bit Linux is more efficient
consumption was
possible in
obstacle
performance. It
than if
and VIA CPUs:
Calculate polynomial with
== EXCEPTION_FLT_OVERFLOW ? EXCEPTION_EXECUTE_HANDLER
constructor for
a1/b1
a lot of irrelevant
called. The disadvantage of compiling
impacts
by another thread.
Optimization in embedded systems
x----
for programs
then follow
development work as
3.6
mask =
2 gigabytes of data.
i); // result =
needed. Even
will start garbage collection when
of information
usually share the same
y1,
Microprocessor documentation Intel: "IA-32 Intel
a common denominator: //
x8*x2;
before p is incremented.
member.
become fragmented when objects of
several functions that are
__declspec(align(16))
all compilers. Some
value of A
also see emulated processors and
bits (YMM),
approximate comparison of doubles
function type
direct hardware access. Available
tell how many times
b*2.0/3.0
overlap.
dynamically when the
that destroys
be able to evaluate
is accessed most
of a linked list
(SVML). This
each object. A little-known
general literature on algorithms
free. These
&list[0];
speed here
sin(x); z = y +
the many people who have
that it can be represented
deleted by another function and
after the
linker extracts the functions
You may replace
be overwritten,
query
of the matrix is a
order to avoid that
larger memory footprint
vector size. Unpredictable
jobs and 10
of objects is high
Monday = 2, Tuesday =
exception handling even in the
hand, does
handling for
is certainly
line size may possibly
response from a hard disk
below, on page 15.
vector
overlapping
int a, b, c,
framework should
absvalue, largest_abs =
quite substantial.
7.28
one that saves time
been identified, then
vector registers (XMM
are.
64-bit device
reading
iterator in some cases, but
sticks may not
optimize the code and
same register. Everything
hash map. Do
special
faster,
function name Instruction set
be shared
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people
routines, system core and
or 1.
(y) { F1(a); } else
make aligned
issue, as you can
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limit
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D language allows
because the offset
Enums
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from doing multiple
actually adds 16
available
stored on the stack in
temp.
< 1000;
covered
derived class is implemented in
80.9 512 512 378.7
the area of
is no difference
therefore more safe than the
each version void
consuming, especially
high-level
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machines? Possible
a program then
entire cache line to be
is a standard for specifying
how many times an
load.
On most
7.13
(n) { case 0: printf("Alpha");
integer, then
16, 32, 64,
processor may have a
condition inside the loop does
miss on
!= INVALID_HANDLE_VALUE &&
not. There are
variable:
141 #include
The dispatcher
See page 43 for
"Beta",
CPU-intensive code,
look
is no clear
and map are
much more resources than the
etc.) inside the loop.
generality of the STL
loop does not cost anything
executable
Greek[4]
on large data sets
more template instances will
a variable which is known
and classes. The object oriented
and destructors
the dispatcher function and replaces
a name.
28.
the eight-element
Lowest
136 ... for (i
time it was programmed.
libraries do not always work
return statement: // Example
and direct
bool a, b; b =
operations are not used).
with a password. The
InstructionSet().The following example shows
C++0x support.
return from functions that
errors
data. A complete
from string functions.
and another
parameters Function parameters are
stride,
dimension may preferably be a
You can divide
linking.
pipelined, as explained above, so
what you are doing. See
relocation. All
1,
r + i/2; } }
recovering from error
up then it must return
printf("Alpha");
expression -(-a)
the counters when you
optimize/#vectorclass
the vector. The other STL
This behaviour
to a function in
is a structure
difference between a
in 32-bit mode, for reasons
allocation. This method also
127
library). The D language
reproducible
implementation is best. These
Loading data
rarely enough
each process.
{ sum
= 2;
what
handling option in
96 9.9
page 107). Agner's
PathScale compilers can in most
to around 1980 where RAM
waste
platform __GNUC__ and not not
at compile-
times 24 dramatically for
mode
bits. The method
it takes to execute the
different integer
Sometimes it is
153 spends
has i
code. The second
of Java and C# and
(a&&c)
high price,
ways. Example:
(YMM)
auto_ptr. Smart pointers can be
u.f and
processes running
number of vectors. 12.10
a[], int * p) {
Wednesday = 8, Thursday
a sorted
is no guarantee that all
with pointers. The
CPU.............................................................................81
cumbersome
following methods may be
needs them. Pure functions A
2n
The advice of making
..................................................................................................................... 38
When considering whether
AMD:
and string manipulation Mathematical
reuse the same
16 16 32 8 32
is used by exception handlers
128
table 8.1 below.
particular integer
comes
optimization features of
and the throughput of
compression
extra time if
.......................................................................................
new version without the need
biggest vectors: for
another thread
this important new update or
(0, 2, 4, etc.). Older
expression
8.1.
seconds; // incremented every second
a+b=b+a, a*b=b*a x
{1.1,
independent
disk if
once.
processing, data
has the feature that there
the alignment requirements are
static. Example: // Example 7.1
line by line when it
is possible to give each
by making the full
100 floats for
// Define size of squares:
safe if multiple
the same cache, at least
that was unknown
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make the division
with Intel processors. A
of the Gnu
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option)
also relevant
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Sometimes it takes hours to
void
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size cannot be
period and by the
part of a program, especially
computer,
Example 8.19. Devirtualization class
newest processors. Supports all
worst-
aligned,
Debugging.
or micro-op cache.
pointer has been loaded. This
then transferred as
and the speed
functions are not compatible across
Intel compilers.
-msse3
space has become too
processing unit for other
is used for storing
permissible if the
developed a test tool for
can also be eliminated if
sums
compiler can also use
return addresses (i.e. where the
the linker.
the computer is restarted
keyword far
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are making
Some application programs
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one iteration to the next.
Studio 2005).
the cache lines follow the
is known at compile time
reciprocal:
is faster if the number
to and you can do
Vec4f polynomial (Vec4f const &
if the condition is
may improve the performance somewhat.
functionality without polymorphism
x-xxxx--x
so a
for multiple purposes. Floating
ebx
// Catch exceptions in
will take 1000 * 100
if the loop counter
to call. I
distance in memory
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likely be
How
If the compiler doesn't have
-fno-strict-overflow. You
not be safe to
be loaded
scanf.
At
-msse2 /arch:SSE2
important
...................................................................................................................... 33 7.5
c2
Address
the appropriate instruction
course. A
// Example 7.1 float
a*1=a (-a)*(-b)=a*b a/a=1
arrays and where the
interface,
different integer types Unfortunately, the
to 15.
flow. However,
__m128i c =
other languages that do have
but read one
the program will be unable
(SIZE
matrix using example
precision if
code is likely to execute
load
by type-casting i to
% 3; }
Calculating
some types of expressions and
The size should
d, e, f, x, y;
functions or when accessing an
to metaprogramming
more efficient than if
inlined.
It is not a
are indeed
b and c are
8.6a
element in list,
not an issue because an
compromise when
frequent if the time slices
case of overflow and
temp2. Modern
for-loop: i++; } }
market is developing
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class. Which
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f=i;
destination both have addresses
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most cases the microprocessor is
Unfortunately, this method doesn't
All dynamic memory allocation using
accessing container elements
hardware platform has become
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it might be possible
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are too large
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don't
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= 2; } The loop
64 32 16.4 65
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they are uninitialized or
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of making sure that one
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that the system code is
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using example 9.5a on a
table that is
to work for
Newest
single instruction. The
assignment
backwards.
Compilers cannot make floating
then tell
8.12a
libraries............................................................................
1. Optimizing
one of the elements in
workstations
in table 9.1 show
is possible.
there are no big arrays,
modification if implemented
optimize register
performance for vector intrinsics. Digital
Aligning dynamically allocated memory
fast math and
unrelated
representation of the
is freed when
capability
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/ 1.2345;
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transpose(double a[SIZE][SIZE]) {
are of
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as floppy disks and USB
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not fit
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pow The method used in
the SSE2 or later instruction
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file and compiled
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2015
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18.2.
kb /
loader.
the Intel compiler
in the code itself
users.
the structure y into
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higher resolution
parenthesis
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run any code branch for
Intel,
+= 1.0f; } The two
on all sizes of matrices.
out if
AVX512 float
table takes
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common excuse that "we
mouse
any cost in
Table 9.2. Cache control
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all allocated objects are
approach
chooses
Enums ...................................................................................................................... 33 7.5
i to
the 61 function
Induction; ; a[i+1] = Induction;
Example: // Example 14.12a int
them. Some important
instruction set specified. Insert
accessible from compilers
that processor model N
shows.
will have more references
unacceptable
data cache is 8
a pointer to another
page 38). Is the
infinity or NAN. Avoiding
better than its reputation.
memory. This may be faster
cause a cache miss. But
is delayed
s2 = 0,
entries.
min &&
use exception handling even
if it had
files need to be converted
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in other threads
$B2$2 ; Induction++;
avoided by calling
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documentation for detailed
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than floating point
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+ d.x; a.y = b.y
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instructions for fast access to
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or class that is
// Example 7.2 a =
/arch:SSE3 -mssse3
if an exception
several times
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After first call it will
threads write
The keyword static, when applied
discriminates
42
The object that looses
declared inside the
object owns. A
a generic version
each set. If the cache
binding definitely
platform-independent and compact. The biggest
of which optimizations
/O2
pure function.
distributed
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cannot be shared. You can't
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debugger.
doing whole program 81
ISO/IEC
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purpose, or you may use
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zero.
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version int CriticalFunction_386(int
the function could
elements. Example: //
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exceptions: while (i <
of the Boolean operands because
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function libraries have
whenever a smart pointer
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for mixing single and double
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preferably 32 for
prefetch
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in an import table
of precision. Let's repeat
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algorithm The
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code. The library has preprocessing
ABC 123
compiler and it understands only
an inlined 15.1b
the loop counter.
solution is using one
from the leftmost column
chosen as the
pointers may be replaced
............................................................................. 84 9 Optimizing
of longjmp if
(Embarcadero/CodeGear/Borland
a global variable means that
may be only
the registers eax, ecx and
then you can have
force
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of counters in
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} // Approximate
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addresses. Especially the use of
the function is called. Lazy
you cannot swap
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Intel-based Mac OS X
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abort(),
errors in cases where they
with the same precision
20 3.7 File access................................................................................................................ 20
code further
162
processors that support it.
the memory block
points with the
in the majority of
biased allows
14.7
14,
from integer to
example 7.43b is
breaking out of
as integers: // Example 14.27
12) are more useful
understand
maintain. Most
techniques of
Many function libraries are
changed freely.
page 105. Floating point
is equally efficient. Simple function
return &CriticalFunction_SSE2; } //
by writing: __declspec(align(64))
Intel and one
infinity
__INTEL_COMPILER 161 32 bit
www.gnu.org/copyleft/fdl.html.
is indeed
column-wise
first operand
must always
shows first the runtime
very stupid. Some
code goes through the following
register, add the
are double
constant
sizeof(b)); 47 Most
as a function library
bypassing the so-called
or class objects.
satisfactory.
squares
templates instead
assembly language. See page 141
systems).
applying the
functions. Alternatively, you
graphics
compilers has
the behavior of static libraries.
repeat count is odd and
overdetermined Boolean
+ b)
example. The only
only slightly
called. The safe way
more efficiently. It
unused
for char pointers). An optimizing
operations. All
x 74 x
these. The CodeGear,
glibc
libraries without the need to
Example 14.3b
what r points to ;
single step
details. Use function libraries
%1
and not negative
the cases described
the correct
and page 87
for exception handling
with the last index changing
tasks like
Func(int); const int size =
techniques in the present
Float to integer conversion Conversion
it makes
to start
d.y;
a thread-like scheduling in an
1.0f; } The two
starts.
type of parameters
parallel. Modern
speeding
first processors with
flexibility,
semicolons in a loop
system, not by
string constants, array
microcontrollers have
#pragma vector always Optimize
2006
constructors. A class doesn't
options for the
16 4 64 MMX
the object pointed to. For
64-bit integer, signed
A positive
without using the normal
because a float uses 32
xor mov $B1$2: mov
Should
checks whether
type such as
calculations. The code
will get time slices of
const double log2 = log(2.0);
plug-in
of CriticalFunction
that a compiler generates to
pointer is then de-referenced in
has only one CPU core
The Clang compiler combined
3.10
cannot be controlled. Small
add_elements(s);
x) { return x*x +
to the different versions
you may of
thenaandbcannot use the
/arch:SSE2
than short
are one byte longer in
independently of
rarely justifies the
page 93). All
they are used. It
or array coincides with the
disassembly
way: There are two
many users. Firewalls, virus scanners
very large runtime framework
coefficients double Table[100]; int x;
int Size()
it calls.
therefore not possible
from main through an imported
8.1. Comparison
than comparing i
instruction set is available then
Linux and 32-bit Windows
primitive,
predict with
is obtained by using a
value, n. But
have tested
Intel CPU detection
Example 8.7
contains
12.4d. Same
same memory areas.
interfere
maintain.
pool,
be so many
pointer. It is recommended
explanation of this option. Use
run. Both the executable file
integer.
case and
in a simple test setup
the offset as a
and C#
in the interval from 0
return _mm_cvtsd_si32(_mm_load_sd(&x));} The
the operating system has support
There is a lot to
using an Intel compiler, then
// Non-polymorphic functions go
undocumented
complicated cases cannot be vectorized
serious limitations to
Intrinsic
functionality.
one for AVX2
environment block.
39 matrix[i][j] += x; This
(e.g. an
pointer or reference parameters). The
bit,
note:
Running
memory allocation
dynamic
= 128. These lines are
overflow: //
next two instructions
be improved in the
go away in the future
on variables
vectors,
the C-style type-casting. It is
of c+b will
elements then this
controversies
register if its address is
is called square
friendly.
system, the more important it
principles in order
limited in
treats non-Intel
extra code. Example: // Example
which is likely
in C, C++
_mm_i64gather_pd
should not include any
reached
implement a queue as
be modified by the program,
your code is
other hardware-related
64 Is8vec8
and Linux, 32-bit
excessive
tell the compiler to vectorize,
Day; if (Day ==
answer questions from
and optimized function libraries. C++
are useful for vectorizing mathematical
seen in 64
Using the nontemporal
// 32-bit Linux, Gnu/AT&T
is an arithmetic
D language. D has
Enterprise
will catch
the next higher instruction
memory block and copy
the nontemporal
handling information. Each function
if both
cheap if they are predicted
an integer can be
s(0.f,
a long delay. See page
of convenience - there is
compiler-specific.
smart pointer (see
of an error; and make
exception is caught by
number generators.
works is of course a
need an
best possible version of
stack and
All non-static variables and objects
generators.
follow the track
Func1(double)
Open files and
or inttypes.h is available then
3.7 File access................................................................................................................ 20
saved
is a penalty for mixing
intervals.
the order of functions
have a niche
&Object1; p->NotPolymorphic(); p->Hello();
this to i and shifts
same object. There
(b1 *
its child class.
safely assume
used for branch
case a
values,
256-bit read operations
indexed
needed
effect is much more dramatic
x4 = x2 *
instruction was certain
sorting
is slow, then the microprocessor
may take 3 - 5
the cache will be
with First-In-First-Out or First-In-Last-Out
hardware.
where operands have
Beginners
can not only improve
List[i]++;
induction variable as
big enough for a specific
not optimized. Jumps between CPU
integer value of
Assume pointer
constant. //
produced regularly.
SVML.
type-casting its address:
can do and what it
write configuration files
member functions. A
here is
lazy binding is that
Reset floating
and 32-bit
initialization
to make a multiplication
can therefore suffer
Comparing two pointers requires only
|| b; This
The following methods
resources. This time is
elements:
in the MKL
follows: struct
a ^0 =
program that calls
Instruction set needed _mm_shuffle_epi8
// INSTRSET ==
significant improvements. Making too many
r1;
embedded systems.
size with a line
13 Asmlib Gnu 64 bit
multiplication } // ipow faster
predicted
containing many
vector data.
8 below. This manual
power of 2 in
performs well.
bus
(FILO)
(MS) x86intrin.h (Gnu) Table 12.2.
to 128-bit XMM and
violate
library (STL)
monitor counters in
Add 2 to
positive or the negative
processor that you optimized
function through function pointer a
innermost
processor has hyperthreading. If so,
119
Optimizing less critical
added to p
Integer size
forces
preferences
rely on
+= 2;} //
a1, a2,
linked together in the second
OK, however, to
transfer of a
general.
{ seconds
is mispredicted only one time
stronger
these categories: File input/output
describe
subexpression occurs more than
is interpreted as an
one other function. A
the other way three
different memory areas,
the while loop because nothing
data sequentially A cache
compares
(XMM)
automatically.
first object to the vector.
compactness,
(b[i]
storage.............................................................................
though less user friendly.
ReadTSC() { int
i < 2;
calls to a pure function
vector processing
% 0x20
K8 0.24
goes from the
laws
multiple CPUs or
arrays by well-tested
current operating systems need better
0x20,
b2, y1, y2,
64-bit Windows
example to
time to call a function
generate a bit-mask: __m128i
; parameter 1: 4
therefore preferably have a balanced
Alignd(X) X __attribute__((aligned(16))) #endif const
34. In
of this polynomial
r; c++) { // loop
is a sum of
relevant when
warn
If n
initializes
be vectorized,
fine-tuning,
calculated much
programming language and development
and only one, auto_ptr
possible version
Fortran are based on compilers.
of transferring
else if else if else
modules. This makes inlining more
imprecise
a[100]; float
Induction; Induction++; }
protocols and standardized
can be added to a
for doing two
point calculations and the loop
In such
8.18
goto CFALSE; } }
Some 64-bit compilers
flip-flops,
frequency dynamically depending on the
systems also have
10 elements
algorithm (e.g.
options are incompatible
anyway. You may preferably avoid
CriticalFunctionType(int
unfortunately the unit-test does not
users and much
reciprocal_divisor; reciprocal_divisor
Some applications spend most of
2 when multiplying
generation class (CParent<>)
with different set
c1+TILESIZE;
timingtest.h
well thought-through approach to error
then you cannot rely
is fastest. The typical
"Inner Loops: A sourcebook for
b different so that they
a/a=1 --------x a/1=a x-xxx-x-- 0/a=0
shuffling can sometimes
problem is likely to
Total size of vector,
5 } }
absolute
member pointer refers to.
member functions are less
The Pentium 4 (NetBurst)
efficient than frame functions for
DelayFiveSeconds() { seconds
a.store(aa+i);
later in the program flow.
increasing the
viable
past the
Currently
rows/columns in matrix 96
video
14.8
(IDE) supports multiple programming
compiler can look like and
to modify a double
handler,
+ log(c[i]);. This would
Linux also applies
fast if the table
unsigned You can take
operations are useful
when shared
second generation class
bits 32-62.
to all class objects
want
through a pointer to one
segmented
now contains
μs
instruction sets include
and c __m128i bc
a variable until the
c2 =
can't be reached with
studying
cases where it makes sense
can force
independent of the value
of integer
eliminated if the target
received data in
+= list[i+1];} sum1 += sum2;
suffer
a programmer may prefer
<float.h> #include <math.h> #define EXCEPTION_FLT_OVERFLOW
than the table lookup.
manuals
4 int
Consider the
1./720.,
hope
a branch that chooses
(~a&c)
exceptions. The
user settings
dispatcher should not look at
one version
Unfortunately, the CPU detection mechanism
them off or
64-bit addresses
signifying one
1./6.,
#define directives
possible and by
((C
anywhere
list[300];
C/C++ standard specifies truncation so
= 0; i
address is in edx, to
7 program
c = d
loop counter. Any
the solution
loop is inside another
= 1; }
contains well-tested libraries for many
and operators ...................................................................... 32 7.4
not part of a
with many different
kinds of operations
compiler with
sources of frustration and waste
Sutter: A Pragmatic
detail
call to
which happens
test sign bit
operator[]
to solve this problem is
test,
endian storage (e.g.
an intermediate code
for even the smallest
data structures for
153
C++". Addison-Wesley. Third
Yeppp.
and discovered
Table 18.1.
The undocumented Intel library function
rely on compiler optimization
2 32 8 64 4
as explained in example
generate the
use a set of special
obtain most of
powers
it is faster
program optimization.
need to link
multiplication can be replaced
trivial programming work automatically. The
the conversion takes 50 -
are also included. Combining the
versions alternatingly several times in
Example 9.6b. #include
at what happens inside
capabilities for 32-bit and
the 145 SSE2
well-tested container classes. The standard
calls.
// Dispatcher
may prefer to use the
properly. Many
results or fail completely because
accessed from any function. Global
optimal to do so (i.e.
while loop in example
An inline function is
compiler to predict with
// Floating point overflow
decide to do some measurements
a signed integer if
available, we
operations slow
unaligned reads and
less precise floating
code mixes float and double
once,
cannot assume that an
common denominator can even be
cause fatal
examples in these
Function pointers ...................................................................................................... 37 7.8
buffer and read
execution considerably.
through a linear array.
xx-xx--x-
Another possibility
*= i; return f; }
alloca was
a loop if
= (a1*b2 + a2*b1) /
Writes to a
Those who are satisfied
store intermediate data and local
& a) { return vector(x
constructor sets all
using templates. Ready made
p is therefore
had in fact only
shortly. The following examples explain
table with two entries.
The use of structures (without
popped
hardware-related details depend on
can be quite inefficient if
malloc.
for double precision.
most
interface calls.
on CPUs with a
structures in the
is advisable to make it
account in the software.
programming. The CPU
to 15.1c,
test feature
have no native
only the time spent in
other resources. There are
incremented, while in the former
different compilers succeeded
intrinsics.
at compile time. Are
that my
becomes invalid
aligned arrays with vector access.
11.1b
case then
B1 { public: B2
in each core.
by a blend
satisfied with
9.3 shows,
can bypass
parameter comes first when
assembly
caching. This problem
or two. Often, it
Specifies that pointer aliasing
line 29.
has been deallocated. Failure
is optimized
unknown CPU based on its
other exceptions: __except
while loop, the if statement
of memory called the heap
"Macro loops"
hand, it is
cleanup before
hot spots, but for
Calculate
collection,
be so high
the line that covered
example, all
space is occupied
generality and flexibility of the
(level >= 4) {
a Boolean NOT on a
- preferably
= ((x2) 2) 2 a+a+a+a=a*4
or key press. 19
counters, etc. In
size Time per
an Intel compiler,
a power of 2, so
the execution
109
to zero: // Example
green. It takes
Henry S.
equally efficient because,
12.1a,
counters. A
163 20
assumption is that the variables
forums
signed variable produces a
be inlined for improved
of a particular brand
compute
several examples of suitable
the updates
detects
Vol. 11, Iss.
problems. The
vector operations. You
function because
no function or method
operand is
Security. The
vacant
support in
Likewise, it
Example 14.18a
consult the
different source files for
problems. Avoid
} u; u.i ^=
C++, it is often
executing instructions out
the difference between two
better on very small
code and how
that the numbers
Keywords that work on
In 32-bit
a<<(b+c) - n.a. - -
change during
functions is
not evaluated,
nearest element to x?" or
= divide
branch. See the preceding
returned pointer or reference
develop
the other then
vector size (16 or
Accessibility
activate a particular part
truth depends
a narrow range then
free) causes
in list, the compiler must
used intrinsic functions. It is
static,
calling method in
{ list[i].a = 1.0; list[i].b
should include
set). We can shift out
buffer or send data from
and data caching less efficient.
use integer operations for incrementing
stages
of the STL containers
the available options for the
each. The critical
= a*4 - n.a. -(-a)
12.4a where
/Fa
64 bit mode, we
object is copied by assignment,
s0,
x); // x^1, x^2,
time than other
21
size; i++) { ab[i].b
for big objects that take
to the appropriate function
coprocessor
between threads becomes faster and
mode program is
simple function with
be saved either
above code will fail
the other compilers). The best
(c+d) before
automatically by the compiler.
("CriticalFunction");
Graphics and sound
here.
present in the old
Contentions in the level-1
thread-local
are described
y = d
legitimate
Useful
cache as
nontemporal write instructions are
higher address which can't be
// Compare each element
tasks that
Constructor-style type casting //
with widely
IA-32 Architectures
They sometimes
(iset >=
= (s0+s1)+(s2+s3); Now s0,
the same type to
There is a higher
expressions Induction
modifying only
any
size often have execution units,
code cache. The register
identification adds
has been brutally
void SelectAddMul(short
are generated
compilers). The best performance
by the following
for (r2 =
y2,
taken. A const
table should
supporting multi-threaded software are available
This effect can be illustrated
the same data
m;} template <int m>
is known which
39916800, 479001600}; ...
99
can store the values in
invest more
most cases, but
induction variable (eax)
SSE. Several
then we will
this number of iterations. The
a Gauss
when the loop
by selecting optimize performance
to define
to be slower
79 Floating point induction
a[i].
representation of float,
|| b)
15.0)
database in Windows. It is
both 16-bit,
have no check for
notion of a "function". Multiple
dispatch to virtual member
write 2.0/3.0
pre-increment is
8.26b compiled to assembly:
results in meaningless event
expects
thread-safe function should never
preferably with contiguous
Effective
has nothing
simplest expressions and
time intervals are
*.so)
and compatibility
for (x
a = Func1(2); ...
is other
calls another function, etc.,
of elements Total size of
the | operator which otherwise
// of function
desired program structure. It is
the final result will
write instructions becomes noticeable. The
weigh the advantages
objects without
row + column; Do not
73). Current compilers are
includes the
division
contain the
ordinary
access. 12 Using vector
8.6
it is independent of
performance,
is added to p
completely. For example: // Example
is a disadvantage when the
the message loop of a
example 7.35 page
eliminated if the condition
file level. My recommendation for
thread void
Table 9.1. Time for transposition
= 4
any expression,
typeof(CriticalFunction)
doing arithmetic operations. The
has been incremented,
table increases the
set where the number
:1;//signbit
vary dynamically and
+ 4.; }; // Make
function pointer is the
variables is approximately
that the operating system has
recommendation was the
elimination A
FuncRow(int); int
the least recently
has changed
cache works most efficiently
and other data
(Examples
contention.
more safe to do the
inappropriate
15.1c. Calculate
performed with a realistic
member pointer. This
using dynamic memory allocation.
remedies
patterns.
and sixteen
several standard PC's in a
Microsoft,
and floating point constants are
of functions A macro declared
and compare it
to 3-dimensional geometry and
the rules
under test but also the
9.5b
more efficient to use
0) { c = 1;
Mathcad (v. 15.0)
post-increment.
can cause overflow. For example,
drivers may
2009).
that are particularly important on
currently only
One
unroll option in the compiler.
the standard PC platform
have tried. The Microsoft,
data as
Avoiding
when testing
files while less than 1%
other details that make function
program. This requires no
to use exception handling even
as required, but
{ c = 1; }
wrong type. References are
(there is one set of
unreliable.
optimizing library functions
constant references accept
mirror the entire file
into vector b: Is16vec8 b
dynamic library can be called
+ (vector
prototypes for each
n.a. a*1 = a -
commercial compiler
{ const
Microsoft Table 2.1.
Glibc
coefficients double Table[100]; int
that can be predicted depends
87
should automatically
applications,
queue
} }; // Index out
it does not, and
memory allocation with new
function. Using
in the level- 1
allowed. The code
_mm_andnot_si128(mask, bc); // OR the
void Func ()
this every time a new
you can avoid virtual functions
loop is predicted well. A
A few
Any expression that is
43 about branch
memory footprint is
asa
error message when
crash
I don't think
Some early
Multiple calls to
on Intel/x86-compatible microprocessors. The
certain modification
not appropriate
or class declaration and the
to facilitate
case" values.
induction variables to calculate the
which platforms and operating
34.
in case of mispredictions (see
method. 7.29
Remove right-most 1-bit
are less likely to be
optimization manuals.
frame makes
and a template
message and stop
anything else being initialized.
platforms or multiple configurations
network resources, databases, etc.
possibly be compiled as
cycle on most microprocessors. Multiplication
unfortunate method
data for analysis. If the
A hash map can be
check. It
int a; double
the number of clock pulses
processors is better.
to the most used
alternative
penalty for mixing single and
type conversion // C-style
statements,
should definitely be avoided.
Live
fragmentation.
13.7
no reasonable upper limit
execution units. If any of
This is the function
access. 3.10 Graphics
future. 12.3 Automatic
no extra overhead in the
vector function
mainly on my study of
are a
Neither
_endthread()
microcontrollers:
256-bit integer
pre-calculated
#pragma novector to tell
Automatic vectorization Devirtualization ---x----- x
big structures by
as 8-bit
that calls it. A
bigger software
GNU
allocated object, and ownership
the CPU which can
for how to make this
variables global if
not be worth
stack. These registers have long
combined by some
used, then there
possible. The AVX instructions have
unroll factor. For example,
implementation may look like this:
calculated once,
optimally, or
sum. The trick
last element outside the loop
gets the new
array index.
or inttypes.h is
versus unsigned integers In
Database queries can often be
See page 61.
= B; x.c =
expected to be available
of cores or logical processors
error has
sure the information is
"Hacker's
makefile.
compiler)
parameters. In 64-bit
may remove the memset
reserving
Access
blocking for
memory. It will not use
and then calls exit. Calling
while high-level
eax, ecx and edx
little-endian
to problems of overflow
program. The use of structures
14.7b
Math Kernel Library.
No link pointer
page 96.
easier to understand when
processing, and
Itanium
two 64-bit operations
files to be installed.
worst- case
Wednesday
-parallel
own error handling system instead
If hyperthreading
have extern
not need relocation
cycle on
unless the SSE4.1
function called
pragmas
testing, verifying and maintaining a
whether
renaming mechanism
and integers ................................... 141
above the diagonal. The
hardware identification.
that N1 =
bits
connect
that they are.
aligning dynamically
y = cos(x);
modulo.
the compiler to predict with
test data
b) >>
different. 64-bit Windows allows only
template<> class
lrintf (float const x)
operator is used for converting
neverthe-
long 64 8 512
exceptions
fast as accessing
F2(float
consult
some other functions that
Dispatch on every call. A
negligible when
of container
Time- consuming library
system code
in this column. Number
diagnose. It is the responsibility
reasons why object oriented
subtask
0; } The indirect function
It is important to note
require a
processor the user expects
not. The Intel
calls the critical function ten
manuals. Please
m is replaced by its
same processor core
actual clock frequency that the
a lot of modifications to
select the best
amount of RAM, a lot
efficiently.
not. There are various
odd number
own memory block and a
integer is converted
run most of its time
No
import table and possibly
and the destructor
without restrictions. A GNU Free
been reduced
variables and objects
options
install a large runtime
latencies, throughputs and micro-operation breakdowns
system devices and
Position-independent code..................................................................................
that you analyze all
function for each different
float. The
function, but it has
looses ownership of the memory
of an exception
and compact. The biggest
constants in the entire program
40 i
/ unsigned
its API. In some cases,
for matrix a:
the many rules of
summing
program under
calculations,
the code to a
big endian storage
catch an
Vec16s Vec16us
loaded,
statements, as explained on page
the 64-bit extension
page 107.
container. Can
*(p++) |=
is important. An
// AVX supported return
and non-constant
// Calculate polynomial The
what kind
exceptions can
are needed, but only
Supports parallel processing, OpenMP and
more time. Single
hardware often requires that
of the data block
leak.
through a hidden pointer. The
sign bit so that the
linkage table (PLT) that
a technological point of view.
automatically but only
pivot
2;}
only when activated by the
the more
struct Sdouble
Initialize
is ambiguous and may produce
convert these types to
: 63; // fractional part
y?"
array is not
down and
<<
disk space were
re-allocation is needed.
with the option -mveclibabi=acml. Agner's
4 floats exp function of
7.1
Implementation The
predefined
is intended for
take special
the const restriction from a
| 0
kb.
the latter function also has
most. The opposite of register
reductions: a+b=b+a,
innermost loop of a
/FA
a[size], b[size]; // ...
best on processor X?" rather
regularly. Intel: "Intel® C++
sometimes have unacceptably long response
class is less
// Function prototype CriticalFunctionType
which would be an
unrolling Some compilers will unroll
compiler is mostly compatible with
each. The critical stride
= b ? 1.5f
reinstalled and user settings are
to pressing
costs. The time it
Example 14.18a float a,
5
moved.
for discussions. Turn
that can be divided into
AVX
result can be
copy that
an integer is within a
number of clock pulses since
lookup process is
sequence
register to
but none of
footprint
be advantageous
performance somewhat.
has a table of
combined.
100000001.23456.
(properties)
calculations.
or #pragma novector
;eax=addressofa
two comparisons i < 0
constant,
branch mispredictions. Test the whole
Example 9.1a
other platforms as
i <= max)
x-xxx----
from example 16.1
frame- pointer
size)
generations
web
{...} // AVX
stress the importance of
__attribute__((aligned(16)))
The advantage of using ready
{ return _mm_cvtss_si32(_mm_load_ss(&x));}
Nothing
to be transferred in
needs. 9.8
parameters then make
object. It is possible
cache line. Some compilers will
many bit manipulation
4 processor. Extra
a bitfield by the use
"C" declaration and the
i = 0 that r
main,
file access or
Many
new. The purpose of
oriented programming without paying the
dedicated physics processor for calculating
questions
value depends on
to be reloaded eight times
vectors requires
i+1;
hardware circuits consisting of
nontemporal
full 64-bit
esp
determine
case of an
x; x *= x; n
_mm_i32gather_epi32
16 clock cycles, depending
where the data are
v. 9.0
can be an advantage because
makes sure that no overflow
c*x +
instruction
list
DWORD PTR[ecx+eax*4],ebx eax,
languages.
until the next time
always keep up
if),
Remove
certain kinds of code
bb into vector
CGrandParent
well-defined
objects are accessed in
the program. The advantage
restores
branch depends on the calculations
pattern, while Pentium
The number of branches and
(b1*b2);
(*SelectAddMul_pointer)(aa, bb, cc); }
Loops......................................................................................................................
physics processing unit intended
the condition
modular.
a zigzag
you to
be expected.
double b[SIZE][SIZE])
-1 (a&~b)|(~a&b)=a^b ---------
60 The
// Roll
x^4 // x^8 //
= Func(ab[i].a);
in the best cases.
other address
Intel's Math Kernel Library, available
rely heavily
WhateverFunction(i);
Agner's vector class library exp
of a and
data members within
various
today,
(PLT).
source,
In some cases, the Intel
example 13.1, Requires binutils version
core library contains
advantages of C++
the code size or data
integers, as long as you
size. In other words,
[esp+8] DWORD
table
24 6 Development process......................................................................................................
Pentium CPUs which
The AVX2 instruction set
below. Cannot
class. The
b.
p1->Hello();
offset of b is
(Windows: /Gy, Linux:
(a+b).
understand when
a hot
keyword is used
* 32
correct
Technical
polynomial:
a reliable decision.
while you can only
about in my
overview
because they cannot
shuffling,
8 bit and 32
make more efficient
memory pool. See www.agner.org/optimize/cppexamples.zip.
d; //
the compiler .......................................................................................... 66 8.1
1.0E8, c = 1.23456,
no side-effects and its
Func1(list,
information about pointer alignment and
parallel calculations on vectors of
of structure or class objects.
libraries use dynamic memory
efficient alternatives
allocation. There is no
replacing a function call
matter
function is called through
line, because the threads
SSE4.1
evicted.
---x----- x -
implementations. 7.22 Inheritance
Function addresses are obscured
A static member
whether r is
minute
past the end of an
memory. If
different sizes of the
"Gnu
level-2 cache of 256
input
is unstable or if
these directives are compiler-specific. You
operator + (vector const
b[1],
non-Intel processors can be
several years before
artificially
(columns
different type by type-casting its
optimized,
data and make
it is accessed through a
accessible
const keyword tells
2.0 This
for several iterations of
reads.
likely case that the
spots Before
fact accessed
profitable to use
1024/4
error in the oldest
an entire cache
following features: The code
stride is 8192 /
anyway. Pure function. __attribute__((const))
instead. The Gnu libraries
this block:
overdetermined in
the vector class library, SSE4.1
The latter is
has been doubled. Thin clients
Intel math function library with
Single-Instruction-Multiple-Data
because the stack unwinding information
processors, as explained on
database integration, web application
nonzero floating point numbers can
positive number when converted
different instructions sets.
Conversions
LoadVector(void
capabilities.
code carefully to
0; column < NUMCOLUMNS;
0 264-1 uint64_t Table
ja
unroll by two then
dependency chains, especially
This worked
hasn't thought about the possibility
functions (i.e. Microsoft, Intel and
the specified instruction set.
by another thread void
task is often determined by
33
in a hardware definition language
matrix // call transpose
they don't need
integers as Boolean vectors, and
to replace arrays
Example 8.10b
public data object: (1)
matrix[r][c]
speed. A
until the previous link
address.
known to be an annoying
because of a very obscure
may reduce this to:
but i*12, because the size
.NET,
are called. The program is
structures in the end when
atomic.
where a vector implementation is
key
ahead. It
never be negative
row-wise,
instructions,
provided as an example in
lookup cannot be vectorized
on it. Instead
spent on executing instructions
different tasks.
function means that
mechanism stores a
while many
4; Register
when choosing
the history of CPU development,
correction
frameworks typically
share the same cache, at
resources than doing
inefficient
7.16 Function
an extra register
It may not
logical processor is
N:
library is very large
quite inefficient. The modern
devices,
select function, and
(20 - 45
polymorphic function. The
and normal
has the correct child class
is rarely needed. 11 Out
confirmed
needs. The
x (x)
called near each
restarted
declared. An object of
dispatcher treats non-Intel CPUs
a+0 =
Whenever
devices if
be a better solution. It
accessed, and this error is
optimizes
on and off.
to stack memory
will align data members
(b1*b2); The
time slices.
mimic
allocated memory................................................................. 120 12.9
tested under worst-case
and store it in a
away.
} } The same
of code). If the
it is the responsibility
for multiple variables as long
a base class
not-too-big upper limit
pure. Virtual
may use 64-bit integers if
background calculations piece
a kind
how well
propagation is
contentions will
good code
16-bit systems
the same or a nearby
code" actually implies more
binary digits. The
take 3 - 5
value wrap around. Adding 1
that doesn't handle
double 64 2
= b * 1.2;
between CPU cores. A
frequency is increased when the
set is enabled.
is cached. Usually it
may be at a disadvantage
expect the table to
opens
bits (YMM), and
strings are particularly
type such as a structure
row +
which is very likely
the function prototype: void
b1, b2;
several reasons. C++
shows first the runtime polymorphism:
first byte of zero
enable constant
Library) and other container
Addison-
SelectAddMul
about function names and
VIA CPUs.
becomes faster
calculations:
Small functions are often
for automatic CPU
Fortunately, there are more efficient
simpler when
bit to compare absolute
necessary then it may be
precision require precision
If Microsoft
loop: //
than by individual installation
all dynamic libraries contend for
module static static
modified
3: printf("Delta");
tasks were
be higher due to
floating point calculations whenever
to use the well optimized
in the likely case that
method is faster if
a more distant future.
involving integer addition, subtraction
register variables,
page 87 for a discussion
the fraction is stored
and i >= size
1./3628800.,
used. Do
int)i >= (unsigned int)size)
continue
is critical. The worst
The IPP library
polynomial(x)
precision
multiple cores,
= b; c = b
the same module then
viable compromise when
therefore difficult to maintain. If
String constants
of the techniques of multithreading.
117 12.7 Mathematical
integral
error reporting here: return
x; for (i = 0;
PLT entry with the pointer
line is implicitly
candidates
are using functions
costless
several factors
F1
multiplication prior
the actual processor. However,
type-casted to
predict a switch statement
3, 4, 6,
function library. If
126 13.6 CPU dispatching
then call _mm256_zeroupper() before leaving
comes at
in column
1000;
itself. Another
way. If
upper 32 bits of
MFC). This method may
the {} brackets in which
of the beginning
is small enough
artificially changed
50;
cycles after
two branches to
Return
case, the performance is
against
type, a
for(i=0,i2=0; i<100;
largest
&Object2; p2->Hello();
multithreaded
and micro-operation breakdowns for Intel,
end user. Dynamic linking
modification
It has excellent
FPGAs. The
} The multiplication
constants will be replaced by
member pointers if
functions are listed in the
the case then
SIZE % 128
the answers in
+ r.b;}
series: ex
using position-independent
TR 18015,
or -fsource-asm). This
modern CPUs,
Pointers, references, and stack entries
signed with
We take the
identified.
When you
purposes
benefit from its
- x-xx----x x-xxxxxx-
this: // Example 12.4e. Same
Reading
< size; i +=
Yet,
// If Microsoft compiler
(2.5f
loop-branch
also recommended
efficient. 64 bit systems have
consequences.
reduces
keep the same precision
system is often
is called, a
................................................................................................. 103 12
(methods)
recycled? There
to make aligned arrays
cache cannot prefetch
an application
Intel CPU’s. Another
12.8b.
obstacles to
|)
to minimize the amount
error-prone.
two 64-bit operations so
truth
{ return ipow(x,10); //
both have addresses divisible by
I am giving this example
and fine-grained
count how
again, but it would
service routine should
be obvious
the vector size
dilemma.
513
called only
Call to virtual function
need to check if the
= OneOrTwo5[b & 1];
0.57
c1 for all squares: for
runtime.
an up-to-date
must be inside
containing integers.
situations where pre-increment is
0; for (int i =
though.
is. The
log(2.0)
of a floating point
the first result
language for
or reference to anything
that does floating point
code could benefit
Static versus dynamic
other is -0
Example 8.8b
N&(N-1) gives the
calculate the most common
the entire program
the memory. The
one register less so that
just by turning
4 128 SSE2 long long
must be read
can be joined into
classes ............................................................................................. 113 12.6 Transforming
programming languages
this example, a, b
with the option -fpic according
ARM
reduction
compiled for 64-bit operating systems
either in the
1./4.790016E8, 1./6.22702E9,
be copied into registers. A
} The function F1 is
mov mov
all code branches
r;
by 64, but the alignment
in example
I have provided several
0x20; 46
efficient and you want
algebraic
significantly
is significant if a parameter
64-bit double,
strings.
subsequent manuals. Please note that
C++ compilers. Wikipedia
n.a. 2.23 0.95 0.6 1.19
subsequent manuals. Please note
more resources,
cast The static_cast
possible to do an
real
to integer can
variables ......................... 142 14.10 Mathematical
systems, especially if the
several files
then the multiplication can
a function pointer typically
moved,
32, 64, ...). We
See the compiler
big block of memory
of that branch and other
same object. There is
// Example 8.12b int a[2];
Factors
process
The library function will return
exceptions a
method for transferring composite objects
around at
are used. Conversions of float
register temp in
calls alternately
instructions cannot multiply integers
155 test. You can
basic
form. A
Example 14.29 union
user will be
memory,
microprocessor doesn't
computer.
2.11
susceptible
four float's when the
of the loop counter can
more reliable results.
need metaprogramming. The
have Boolean variables as input
} } } } else
Integers of
scattered everywhere
by multiple threads Parallelization
save by avoiding the
have
// Find
Microsoft
to insert
32 bits of a double
for N
Make functions local A function
vectorclass manual for details. //
behaviors. Arrays
programmed. Therefore, it is
101 Multithreading works more
the processor and
Calling a function through
row < NUMROWS;
?Func@@YAXQAHAAH@Z
possibilities for optimization. For
test feature into
Microprocessors with the
This is safe and flexible,
// square x // get
CPU detection mechanism in Intel
normally belongs
the processor). Optimizing compilers will
specialization, not with
invalid,
a1,
may make some tests with
calculations of (2n
local non-member functions. 80
executed
85
calculated asa << 4,
never spend
that a specific pointer
18 3.4 Automatic updates
cout << "Error: Index
may be situations
example 14.23 page 143. The
have been added and then
contain either sixteen integers of
memset:
will always select the
language While C++ has many
(other than log) inside the
be fetched
instance for each thread. Thread-local
Mars compiler is mostly
Extra memory space
and parsing are
allocation. You
work,
a fully compiled code.
Iu32vec2 64 1 int64_t 64
engineering
and analyzing program
the operating system and
eax,
resources and
niche in
even though it could
relational
reducing the
thread. Pointers to contained objects?
function can throw. In
optimize away a
imprecision in some
developers choose other
of optimizations. The results
list[300]
= 2; Unfortunately, some
microprocessors. Integer
the program 153 spends most
is rarely enough to
allocation of memory for
It doesn't
diagonal swapd(a[r][c], a[c][r]); // swap
rest
It is less efficient
If a function is not
addressing
that the table is
maximum,
unrelated to each
types available. declaration size,
may report
don't understand it. I am
and other hardware-related details depend
integers
the IDE
SSE2 instruction set makes
of security,
operations and choose the
// 8 bytes. first
13.1,
to receive
will be joined together in
powN is
single or double precision,
expect to 99 read from
the same result if
of 100 doubles: union
identification (RTTI). See
for each thread. Thread-local storage
makes testing
one contiguous
is included in the profile.
+ log(c[i]); // Increment
setup
are generally very fast.
may work
in so that they
temp = a+1; b
needed: // Example
performance problems.
file)
profiler which
string; while
by itself. But a
"move constructor" to transfer
to contain all data
block
result ebx is then stored
1; } } A
16. Library
Unfortunately, the standard
except for char pointers.
aa: a.store(aa+i); } } The
the least significant n bits
cleanup jobs
declaration makes
of two different implementations
following alternatives: Make the
? 1.0f : 2.5f;
Older CPUs with
system
consumer if
in the choice
more integer to
typical degree of
to 12.8b automatically and vectorize
useful to copy
units, one or two floating
PathScale. 2.
is and
choose the most often used
sqaure: for (r2 = r1;
soon
member functions have a 'this'
adhere
tested,
information, such
public B2 {
Algebraic reduction Most compilers can
stand
imported
which may be
variable size.
a technological point
light-weight
unaligned op. AMD Opteron K8
a; double b; int
The developers
elements b.load(bb+i);
the desired functionality without polymorphism
64-bit
one container for
type by type-casting its
pointer is deleted. Smart pointers
the generic
call this distance the critical
may vary dynamically and that
forget to make the local
shared object
user interface than on
Template Library (STL) which comes
b * 3.5; c
exponential function can be calculated
only if, a level-2
of costs to multithreading that
area for a
using InstructionSet():
log(2.0);
occur: if (SIZE
update
enable the compiler to reduce
compiled for a
File
classes
These profilers
the operating
called whole
a2
b1,
possibility that a
The &
other way is
the multiplication is exact. Multiple
but unfortunately
clock cycles. Calculations in
versions of the CPU
which method is likely to
be accomplished
insufficient
us
because there may be
r1+1;
float or
(eax)
(-a==-b)=(a==b)
Returns time
conversions can sometimes be
and for fast and easy
functions. I disagree with
to override public symbols, but
the producer will
sets)
new one. I
number then we would
time loading files or
inlined so that the
columns below
binutils
or int 8 AVX2 _mm_i32gather_epi32
works less
addition. If
enabled.
destructors after
include
pointers, references, 'this' pointer, common
conditions using
itself is
c1 <
( short int aa[size]
eax edx, DWORD
other purposes
to have constructors
is the
to write the members individually.
becomes bigger
happened
call a virtual
become a serious
loop will take 1000
systems". The parameters a and
to this the time
caches
accessible from
is definitely
have an option
CriticalFunction = &CriticalFunction_386;
List[ArraySize];
message if it
the child class members.
__attribute__((const))
previous iteration. This allows it
of range. This may typically
number of DLLs, configuration
14.24
OpenMP and automatic vectorization. It
a function but
ways of copying
many renamed instances of the
and a GOT for
current .cpp
// Example 9.2b void
of calculations,
very time-consuming garbage collector
compatible instruction
than signed
x; x *= x;
an integer, then
well it optimizes
variables or hide them
reordering the data
give overflow and negative inputs
costly to
hand,
depending on how
is a disadvantage
105.
all writes to load a
been called
bottlenecks is to
architecture of the software.
;
the cost of longer response
position-independent, makes a PLT
multiple versions for different CPUs.
arraysize)
the throughput of CPU-intensive programs
231-1
into account. You
12.9a. Taylor series
instruction sets have
blog
functions, or if
structures in
process is used when
method
m.
individual array elements more
as entry point. //
and see which one works
divide
requires an
the {}
1];
up cache space.
in b[i]
multiplication, to mix
Such hybrid
10) { ... Conversions
this important new
remove or modify objects
vector.
own
\n fistpl
the memory if
thenaandbcannot
QueryPerformanceCounter functions for
7.34a. Use macro as
throw() statement
examples I
For example,a * 16is
the class Vec16s
bytes smaller. Structure
-ipo
same cache line. But these
prevents it from
Func1(2);
lengths to reduce this problem.
{ return vector(x
A reference
but the compiler uses position-independent
and reusable classes.
function, means that
simple variables, loop
a[N]; public:
(Windows,
bias
be non-zero, and
interface (OnIdle in Windows
(16
next line provokes an
float Exp(float
references are equally efficient
faster and smaller.
register stack is used. It
for interrupt
x-xxxxxx-
of some
timediff[i]
make container classes in
not compatible across compilers.
constructing
syntax:
modularity
Single
based on its
Virtual function
<.
complication
independent of changes
the new value of
and VIA. The
loaded into memory when the
the processor. This
or column. The access
0.11 1.21 0.57
14.12 Position-independent code..................................................................................
frustration and waste of
x, unsigned
functions Some programming
vectorization is.
as possible for usability reasons.
programming principles in order to
manual at
this loop?
are mutually incompatible. A function
called by the rest
address. Pointers
8.23b.
it to. It
the thread function
execution is
memory. This can be done
class. The child class is
of template parameters.
makes sense
with many labels that have
105). If the
platform independence,
Size
a function is called, it
calculations usually take the same
are so big that overflow
with enum,
135 14.4 Integer multiplication .............................................................................................
interval:
You may think
names of inlined
innermost loop: for (i =
81 optimization
operating system to swap memory
data with all
Function prototype CriticalFunctionType CriticalFunction_Dispatch; //
Z;
is created, deleted, copied
+= TILESIZE) {
simpler in 64-bit mode
to
powerful
only for objects
then d+e,
into a single branch if
this address is
actions like a
does not occur. See
2exponent 1023 1 fraction
or C++.
AMD LIBM library.
static or
(see p. 22). 159 18
end users have.
float s0
_mm_mullo_epi16
table of const double A
/arch:SSE2. The
Similar
done as a
allocates one memory
brand, family
uncommon for software
version int CriticalFunction_386(int parm1, int
check after
manageable
would be invalid
to make a new
regardless of precision on most
We can only
measured in this
balanced
and Gnu compilers are actually
Sandy Bridge) because
is not possible to add
is able
cache contentions,
platforms. The Clang compiler
runtime check that
*(++p)
satisfied
module
fine then it is
Choosing
fraction. The sign is stored
instructions without help of
int a[1000]; F1(a); }
union {double
used, even
1980
or structure
= b * 1.2f; //
10 -
C2
containing (2,2,2,2), and store
instructions SSE4.2 string search
an address below 2 GB,
produced
caches.
i is interpreted
pointer in an
39916800,
conclude this section by summing
* 4 = 32. This
decision.
name for the child
such a check
The effect
is discussed on page
A compiler has to
~a = -1 (a&~b)|(~a&b)=a^b ---------
code may be stored
efficient than investing in a
the YMM register
considerable.
According
function is called.
non-Intel
of cores will grow
the loop unroll
unique
instructions rather
Comes
{ int r,
and accessed
an exception. Therefore,
the loop and reorganize: //
the divisor is known
-(-a)=a
number of bits
addresses, or if pointers are
www.agner.org/optimize/cppexamples.zip. If
is repetitive. The
You cannot expect a directive
polymorphism.
less computing resources than standard
while most
vector. The other STL containers
CPUs".
series of calculations, where
the address of the array
an attribute which can be
than 33%
important that the
additions. Divisions
as i
language has full metaprogramming
to temporarily lock a container
if (absvalue >
Development time
code is fragmented
98
reason that they
int row, column;
the execution speed
both get the
a*1=a (-a)*(-b)=a*b a/a=1 ----x---x
calculations then you
only one CPU core
$B2$3: ret ALIGN ;
extern "C" int
Only the
give
to integer can be
actually more
Espresso) that can
case.
The user expects
order. Example: // Example 14.9
qword
LoadVector(bb
value of
for local references. If we
advantageous because registers is
a[c][r]);
aware of.
-S - masm=intel /FA
vector division. 12.4
example, the conversion
u.i[1] ^= 0x80000000; because
latencies.
between efficiency, portability and development
on performance. 7.18
will be better because
= s; An integer
D :
the speed here
poorly for the end
bits Instruction set char
jumping around and less efficient
on, then it will run
doubled. A thread that
resources cleaned up.
use situation where the network
access. Available protocols and
speed Testing the
can be optimized if a
107.
more then the offset
x-xxxx--x Profile-guided
are not. Supports 32-bit and
values
appropriate.
of performance on AMD and
programming style. The time consumption
be reduced to always
set Prefetch PREFETCH _mm_prefetch SSE
is AND'ed with the inverted
support,
called when
}; class C1
other are also stored
reduce example 12.1b to
less than 128
loop body begins
(2,2,2,2), and
type of
are approximately six integer registers
exit the
16.2 calls the critical
only a single function or
16.
method.
or static or by
consumer if it involves allocation
set control no
14.14b
the program must clean up
Adding 1
stack frame makes
operations,
are called. The safe
busy concentrating on
This data conversion and shuffling
starts
point registers and correspondingly two
under the worst- case conditions.
int)(max
1.1
// Example 8.2a
by choosing the
dependency chains can be
of the polymorphic functions. The
use different
compilers may be
1024 bits
64-bit programs to run
debug breakpoints at every function
call to a
process running when
and delete is to
to take advantage
make a function local: 1.
known before
Use intrinsic functions Use
Mac. The Gnu compiler is
profile-guided optimization.
Vectors
(6
it
Time-
units,
mutexes
Several function libraries published
38.7 512 512 2048
space explicitly when alloca
up to some positive value,
or const reference
p;
// Example 8.16 float
and it
result is the same
type int.
errors in C++ programs.
occupying
compactness
scan instruction and
y = sin(x); }
textbook on
unused returns // Volatile to
right = divide by 2
counter. Example: //
very large data
for the Intel Core
may ignore the problem and
for inlining a function if
better.
is a very efficient way
PC platform. However,
-msse2 SSE3
function is called a leaf
The Boolean operators produce
longer time. It can
zero within a
precision, but
for the instruction set that
longer used and
code. The reason
64-bit operating systems.
int8_t short
_controlfp_s(&dummy, 0, _EM_OVERFLOW); // _controlfp(0,
listing reveals
for one segment
a double takes 8
at vectorization. 3.
and the critical functions
by subtracting
const x) { return
overhead cost
unknown at the time
b+a,
allocate
||,
.......................................................... 107 12.3
line: static
flip-flops, multiplexers,
expressions also occur quite
occurs in each
x---x---x
instead.
or double because
platform. Intel
work. Data
2-dimensional
not work on
functions have no check
32 bits
6,
time on deciding which
.................................................................
be calculated in advance.
between different parts of a
a*0=0
The string classes allocate a
See page 153 for further
fail if both are negative
7.32b
facilities
Now s0, s1, s2
sched_setaffinity).
cannot be executed as
{ goto CFALSE; }
multiplications. How was
preferably be responded to at
Code
microarchitecture.
were splitting
three clauses: initialization, condition, and
larger memory footprint than the
well in tests on Intel
AES,
formulas
local non-member functions.
or 3-dimensional
that uses
very much on
iterative in nature,
bit of i ;
See the manual for
manner by
to fix the problem and
refresh
some cases take memory space
multiplied by the clock
non-inlined
by the 107 number
// Example 7.5. Set flush-to-zero
the code if we
has support for
dynamic memory allocation is
slice
sequence in
the first time because it
coincides
development, each
= pow(x,n) As we can
if the compiler doesn't know
be used as command-line versions
can look like and
track of when
__fastcall __attribute((
parameter, so
Example 8.25 void
got
to make a piece
unsigned for fast
dilemma
complicated reductions.
// x^4 F32vec4 s(0.f,
moved. A binary
Supported
network
set AVX instr.
capable of register renaming
prototypes for each version FuncType
powN<true,1>
&Object1; p1->Hello();
0.28
randomness in order to get
is good for the
and you cannot
alignment and the
column <
WriteFile(handle, ...))
as well,
be overloaded or
Sunday,
registers rather
x--
false
indeed
but efficient, way
count is odd and
a cheap compiler for 32-bit
return prediction).
b with a
Library" contains
then FuncC.
specifies
{ short
can disable exception
identification (RTTI)
a simple algorithm
unwinding. All functions have to
to fake an
branch mispredictions, floating point exceptions,
occur. See page 78
x^10
4.0.1.
program happen to
example: //
fixed
b =
a[c][r] =
soon became available because
'this'. We
C++ compilers exist for all
are not suited for
the program in a debugger
the FAQ for
object that
!(a || b) a &&
or update
writing:
A class member variable
is executed even
we want to measure
using static linking rather than
Which of
a matrix and stores the
/ nfac;
from the leftmost
b[i] and c[i]
exploiting
subexpressions, and
spaces for
all the inputs to the
size of abc is a
do manually. It must be
address of the end
give annoyingly long and irregular
the alignment.
allow you to manipulate the
expansions.
put seldom
six in 32-bit systems and
signed than with
solution, but
nearest integer. If two integers
several versions for different
Library" and "Integrated
Are objects accessed
increases
prevent cache
optimization by
= (memory address) /
a compiler generates
is out
reductions Most
a minor error in
lrintf and
implementations of C++, directly compiled
systems and 8 bytes in
should test the
The Clang compiler is
in the list causes all
times the first way
#include <asmlib.h> void CriticalFunction(); ...
destructor.
instruction set are expected to
kept
not support static linking. A
to make and
inte-
code.................................................................................. 148
bit, the
particular brand is likely to
data used in the
230.7 513 513 2056
far from
operator ++i
--xxxx-xx a*1=a
$B1$1:
as additions. Divisions
_mm_blendv_epi8(bc, c2,
powN<true,N-N1>::p(x); #undef N1 } };
void CriticalFunction(); ... // Use
is often easier to
the compiler doesn't know the
says.
I have ever seen can
a matrix using example
if a and b take
sequentially. It works
not the case we
the clock frequency is limited
is poor
bloat. It is common for
i < n; i++) {
SSE2 and later instruction
the performance dramatically by
the effort. Square blocking
// Loop counter //=2*A //=A*x*x+B*x+C
+ 1 is
pattern,
a[i] = *p +
use branches, provided
minimize the
cores, and
able to predict correctly whether
cache MOVNTDQ _mm_stream_si128 SSE2 Table
cannot make
some things very smart
int unsigned char 8 0
compile time. //
files).
executable file
---xxx-x-
stride then this can cause
function through a function pointer
one thread than
virtual table. Unfortunately,
make overflow
counter is
care about
3.13 Memory access Accessing data
driver.
pointed
the goal of
most important addition to
serves as
that the operands
compiled. #if directives
supported");
by random events
updates.
relative to
calculations. Even
audience
Windows and Mac.
#include <intrin.h> long long ReadTSC()
principles are
as many encryption
on the hardware platform and
and more error prone. A
see the excessive memory
return route.
several different ways of
have more references to
another
27.
a short
loop counter when
non-AVX code. This
function pointer
get the value 10
mode. See the
or integrated in
doesn't compromise safety
or reads to the same
decreased
8.9a
functions, trigonometric
course that reflects
? 1.5f :
/Fm Generate optimization report
processor core. Try to
Code that is
also work, 133
a register except in
Time for transposing and copying
lrint. Unfortunately, these functions are
Threads are useful
Even
was called
this topic,
functions are included
used for prefetching data
IDE's
list[size], sum = 0;
use vector classes,
usually take
casting, but
Extra
2 can
database ...................................................................................................... 20 3.9
table from static memory
wrap
different microprocessors, different alignments and
TILESIZE // Loop r1 and
parameter to the
A thread-safe
single-thread
exceptions in this block:
one array
(a&&b&&c)
different alignments and different
to the different versions of
mode or
together
is not an Intel, even
122 for
which part
1.0f;}
cost in performance. Integer size
incomplete information
taking cache
cc[])
of 32-bit
All x86 platforms (Windows, Linux,
calculations whenever they are
if the unsafe code is
error messages
increment.
T+6,
"standard
changes of the
Dispatcher.
static link libraries. These factors
a significant amount of
Adolfy
test setup but slow or
through a pointer to
compilers are not very
Compile
specific CPU feature
// Implicit
number of integer register
about an
FuncB, then FuncC.
+ C; }
is used. For
solutions
the next vector, and the
jump to a
possible to do such
how the if branch
a float,
are very similar
strictness
scalar (Scalar means not a
they can block the execution
propagation,
attempts
x,y
noalias) __restrict #pragma
there are a
(XMM), 256 bits
also prevents the
isolate
n.a. a+0 =
p(double
seen, is certainly a
dynamic libraries
---x---xx
simple tasks. Sometimes it
areas.
mangling are explained
and divisions are
flush-to-zero mode rather
includes the low-level C language
<= (unsigned
the chosen compiler doesn't provide
this). Use rounding instead
standard is used in almost
the part of the
type conversions:
basis
handles this code.
of an array element. In
41
access these instructions.
Because
which otherwise
for CPU dispatching and
the data cache. The same
to x?"
useful source of
a graphics card
Namespaces........................................................................................................... 65 8 Optimizations in
This
is chosen for the
SIZE = 64; //
program development more expensive and
| (~a&c) a&b&c&d
bytes without cache MOVNTPS _mm_stream_ps
performance monitor counters .................................................................... 155
Example 8.11b
most advanced code version on,
= temp;
ab[i].b = Func(ab[i].a); }
= 1; a[1]
iteration needs the
through pointers or references
objects are
profiler.
instead
programmer does not have to
= 20, columns = 32;
or malloc and free.
64)
To prevent this kind of
Software Developer’s Manual", Volume 1,
2.2 Choice
~,
functions have a 'this'
replace this line by any
likely to go away
1)sign
a loop repeats
printf("Delta");
is a try block. There
it has allocated
mispredicted
queue should
Therefore, 64-bit Linux
parallelism.
Locked mutexes.
the other hand, the
are swapped then both can
to invest
for(i=0; i<100; i++)a[i]=2*i; The
6 2.3 Choice of operating
char, signed or unsigned
should rely on
if the repeat
realistic set of data in
pointer to the desired version
be determined in advance,
} sum = (s0+s1)+(s2+s3); Now
speed.
you turn them
interrupt should preferably
Critical pieces
An object cannot
the thread.
a block of 16 bytes.
If you forget to make
_finite()) and redo
shared_ptr than
int 256 unsigned 256
Other system
short int (16 bits), unless
be wrapped
purpose: Contain one
b+a
4 = 2048 bytes =
objects (rather than
that it adds an
Installing
an inefficient way.
errors.
or model
only the first
two threads with
Newton-Raphson iterations. Here
Graphics and
the DelayFiveSeconds function
Such schemes
operating system, and therefore
nearby
macro,
the table in
pointers ..........................................................................................................
511
Literature ..................................................................................................................... 163
space becomes more fragmented when
to use static
2005;
if a program has many
Files on remote
are: Optimizing for present
time. It simply stores
for relative addressing of
be necessary to optimize
for studying a piece
the most important
up in
which then calls
lookup table is advantageous
automatically. There
guess,
target buffer.
inline keyword is used or
is set in the variable
a hundred times
is OS
first in a series of
list is large because the
big endian
0x8040); See page 145 and
application program
work cannot be ignored if
the functions memset and memcpy:
A code that does floating
more efficient way if
MOVNTQ _mm_stream_pi
Then
certain that the 64-bit
much time
return square(x) + 1.0f;}
or See page 95 and
{ // Define vector objects
performance because the contents
Other manuals
because it makes floating point
time consumers.
on page 146 below. Position-independent
point:
a far
clumsy AND-OR
FuncType
many people who have sent
0.27
may consider whether others
an option that
static memory and
....................................................................................... 24 6 Development process......................................................................................................
task that consumes most
Obviously, the
AVX support. There
be wired for a
RTTI then
linking is used,
two entries.
into a vector of
one thread
Example 8.8a
newest
the programming
its value is multiplied by
Trying
{x
__int64 64
....................................................................................................... 19
may be the
the time slices to
16)
speed exceeding
layers
the error code. If the
ultimate solution would
by using function inlining,
All non-static variables and
Common
platforms (Windows, Linux, BSD, Intel-based
then the instance in main
will work only on Intel/x86-compatible
libraries: Intel vector math
number 6! The
program execution then it is
preceding addition then
and data caching less
C++ implementation may look
ends
graphics function that
cannot use the same register.
Java, C#,
not always accurate, however, and
brands
other compilers can reduce other
to use that for
libraries Test Processor
each statement that calls the
The allocation of
same as if
operating systems").
element zero.
measures the speed
of range (see page 134
-100,
uses a procedure
object through a smart
into multiple functions. I disagree
smallest integer size
be quite time-consuming (see
for updates should
find the one
of these also treat
library).
((unsigned int)n < 4)
absvalue,
pointer to a table
units. If any of the
and causes the
columns;
fourteen in 64-bit systems. 67
1./8.71782E10,
is possible to do
31
- 30 // f is
and) will cut
in a programmable
In order to access
Bounds checking In
p2
45.
has a parallel structure
range from -128 to
linked libraries or
on the result of the
forces the compiler
at the object file
Eliminate
compilers have support for whole
loaded only
recommendation
unsigned integers In most
complications
// u.d
it comes before the compiler
256-bit YMM registers. The first
the addresses are spaced
MultiplyBy
64-bit.
all. Fortunately,
start of the program, and
Long double precision
all. In the case
memory. See
profiler that can tell how
systems and fourteen in
Core
7.31a
edx but the
example, which calculates the
execution,
be divisible
application can make
computer users
values:
Other cases
variables const double
!b)
need induction variables to
of storage space.
heap can easily become
than 8,
do the check after
functions, called procedure
and 3B.
you cannot always
This is useful when
add the last
be available, we may choose
that can
to gain if such dependency
mode. See the manual for
or interpretation
a must
accelerators
j * (columns
C++ and Fortran
many of the advantages
fragmented. An alternative is to
the library file and
says
may replace
structure then
of branch that can
vector function libraries.
long double precision. Conversions
graceful way.
0.5ns. 2GHz A clock cycle
xx4(x4);
objects that
of the 32 sets
you have big
development environment (IDE)
__int64
with out-of-order capabilities are very
Of
X?"
same way, the first processors
because it needs only
is available for free.
the size.
the structure 8
that compiler makers
different types cannot
representation
sizes. Fortunately, the solution
M
floating point addition and
chains
when their live ranges do
{ FuncB(i); }
163
Obviously,
that use these methods
the value of the divisor
jl
s2 =
usually 32. In 64-bit systems
processing
code then you can get
omitted,
= a;
both cheaper
sum of a
0; i--,
for example if you write
are making a
etc. The efficiency of
a variable which is
execution time because the memory
use just-in-time compilation. The
of how compilers and
to one thread than
reading disk files. See page
only on some processors that
create a new one.
= -1.0E8,
example 8.21, you could
clock counts. The
store help
automatic parallelization. The
columns
calls. There are three
Those who
instruction can
it feeds a
slower than intended because
to 36. There may
into vector c: __m128i c
a built-in
1
vector size. Later models
the same thing. Example: //
Float
39
bits Instruction set
you forget to
then the expression
3.x.
{ // abs(u.f) > abs(v.f)
problem are
the code is not optimized.
unsigned integer to a
a * 3; return
inputs when the
be repeated 1024/4
integers. 7.5 Booleans The order
on the advanced principles
can expect
(4096). This will make all
all the factors
faster than the
This example is specific
application,
unsigned variables.
of a data
instructions that are coded in
collection can occur at random
setting an array
15.1b, and
through a
support for relative addressing of
position-independent
the function name is
(page 77)
C
Templates make the source code
in a union:
precisions when
that standard
is inefficient, especially in 32-bit
Overview of compiler
be updated
languages where everything
interfaces and interfaces to network
3.9 Other databases ....................................................................................................... 21
a first-in-last-out fashion. It
code (byte
"worst
much longer
terms
database can
than the level-2
functions You have
pool.
(int
function name
Supports both
members. It is recommended to
zero. A good
of list[i] is equal to
Pentium 4 processors,
inefficient if a program creates
more well-structured
"Intel® C++ Compiler
register.
structure),
most common
self-relative
miss
more resources than the code
with more RAM than end
integer size that is larger
for "assume no
systems, but in registers
that work
0=
Example: // Example 9.2a void
an extra cache
valid only until
optimal,
NumberOfTests = 10; int
ago,
Container
true
pointer in member functions
b)
of floating point expressions.
14.30
faster if the dividend is
a BSF (bit
Underestimating the
a feature called
stride) = (number of
152
the program if there is
game or animation.
operand is not
optimizations that we want
14.13
do something
a list should preferably
^0
as buffers
FuncA(i); FuncC(i); FuncB(i+1);
applications even on such
to the beginning
Some
fetch the
compiler from doing optimizations on
overwritten, and even worse,
................................................................................
way: bool
away and the result is
installation of the program
15. C++ is definitely the
(not
do much of the trivial
69
optimize across the function call.
installed,
with millisecond resolution and the
= order(i); matrix[j][0] = i;
If the granularity is too
to force the swapping of
metaprogramming is the only way
way three times. Then
c;
where there are
overflow,
time. You can
The value of cc[i]+2
// Example 14.4b
&&
to make sure the result
("int 3"); or __debugbreak();. If
maintenance - to
treat
call inline void SelectAddMul(short
90% of
Works well with non-Intel
computer starts
double Y = C;
sorting and
code Assume that a function
threads are areas
an integer in
worse, it can overwrite
longer time. It is possible
telling
length function
code took 50 clock
language".
-ipo No
Sum2 and Sum3 are doing
&SelectAddMul_SSE41;
is free
interrupt 3. The code
Gnu directives work
transfer a pointer or reference
+= sum2; If the
compilers will align large static
induction variable Y // Update
code and lazy binding by
up the data into
n to
move.
parallel if
that a function is not
way. The Codeplay
less efficient. The performance
Interrupt
the best
when the original
several drivers, configuration files
In Windows, you
program is more manageable
the preceding iteration is
size = 100; float
if all functions
the framework, during start
unless you have special reasons
programs spend
A dispatcher function decides
This reduces
u[2]} a[size];
has changed.
Zero
vectors are preferably
for detecting
It is therefore important
reversed if
critical because
that a loop
addresses of array
reflected,
Michael Abrash: "Zen of
integer and double
the factorial function looks like
several other less well-known languages.
copy Function inlining
calculate the address
83
find elsewhere. Faster
time then the sampling
disturb
crash.
preceding iteration
incompatible.
return _mm_load_si128((__m128i
Each graphics
as possible for usability
((unsigned int)n < 4) {
of disk
a:
members. This alignment can
Compiler-specific
}; // constant data
-(-a)
Primitives
executed 10 times rather than
is initialized only the
tables are
call with a table
to list
inline keyword
for overflow and works
code the offset as a
14.21
address of the preceding
SSE3 tmmintrin.h
// vector
f
processors are not
problems of overflow
the code can
bit // u.d is
math core
134 }
//Loopby4
+ d;
regular pattern,
44.
algebraic expressions on seven
< b
pulses
Windows). There are several ways
to the standards for
rather than Boolean expressions. There
copying them
projects have
exceeds
if (a
term for running multiple threads
define application-specific instructions that
in other modules
operation using the |
(-a)*(-b)
volatile keyword makes sure that
2, Tuesday = 4,
tables.
is available then each vector
etc.,
a try block.
is admittedly very kludgy. The
Different compilers
condition is
160 /Qparallel
operand first.
the speed or not. There
not need updating in
same as a
ignore, then the solution
used without
violate or circumvent operating
const,
if the program had
slow implementations of
go the same way
compiled with different
while a
purity.
Intel libraries are used with
seem illogical that
cause
memory pooling. It
latter is more efficient. 64-bit
Context
to it. This is inefficient
programmed. Therefore,
A model
(float const
<intrin.h>
program size, while
transferred
this address. Step (1)
the work load. The clock
operation,
file can be wrapped
vector register size. Vectorized
.......................................................................................................................
Pointer
* _mm_load_ps(coef+i); // s
123 and static const
below. Microsoft Visual Studio
the general case where
normal afterwards.
min)
on page 26. Avoid global
much higher
construct an object with
binary value of i to
such as email and web
} int main() {
for transferring composite objects to
Intel math function
registers. The vector
mechanism
indicates
the mouse. This task must
loop for // multiply //
software packages
Factors that make vectorization favorable:
first call to
doubled. This makes it possible
mispredictions,
though it is doing
17
dictates that
one (see
? a
and they waste a
uninstallation of programs should be
a bottleneck. Organize the
and maintaining a
than rounding. This is unfortunate
template specialization is allowed
breakpoints at
causes misses in
1. Add the
for your application then you
to Func1,
style type-casting with a
a hard disk
time when performance
// Example 14.18c
by 16 is required.
Greek[4] =
intended, while the
bytes without cache MOVNTI
(new and
Environments)
'this'. We can
later.
Some compilers can
one 256-bit
a1, a2, b1, b2, y1,
< 5) {
instruction set available, e.g.
Pascal used an intermediate
may consider whether it
counters when they are
and destructors of each
or data used in the
zero within a block of
controlling
until a few
} module2.cpp int Func2()
shared_ptr
type short int
module or a
case that the next
on all elements of a
that needs them. Pure functions
complicated.
/O3
a[i+1]
removed,
platform-independent
Iss. 4, 2007 (www.intel.com/technology/itj/).
AVX2 long long
API
handling support anyway. The exception
or Espresso)
laws of algebra.
list[ARRAYSIZE]; if (i < ARRAYSIZE
compiler for Windows, while most
very useful for many different
which it has calculated in
// Round to
would be even
