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IA-32 Intel® Architecture Optimization
A-6
Multithreading with OpenMP*
Both the Intel C++ and Fortran Compilers support shared memory
parallelism via OpenMP compiler directives, library functions and
environment variables. OpenMP directives are activated by the compiler
switch
-Qopenmp. The available directives are described in the Compiler
User's Guides available with the Intel C++ and Fortran Compilers.
Further information about the OpenMP standard is available at
http://www.openmp.org.
Automatic Multithreading
Both the Intel C++ and Fortran Compilers can generate multithreaded
code automatically for simple loops with no dependencies. This is
activated by the compiler switch -Qparallel.
Inline Expansion of Library Functions (-Oi, -Oi-)
The compiler inlines a number of standard C, C++, and math library
functions by default. This usually results in faster execution of your
program. Sometimes, however, inline expansion of library functions can
cause unexpected results. For explanation, see the Intel
®
C++ Compiler
User’s Guide.
Floating-point Arithmetic Precision (-Op, -Op-, -Qprec,
-Qprec_div, -Qpc, -Qlong_double)
These options provide a means of controlling optimization that might
result in a small change in the precision of floating-point arithmetic.
Rounding Control Option (-Qrcd)
The compiler uses the -Qrcd option to improve the performance of
code that requires floating-point calculations. The optimization is
obtained by controlling the change of the rounding mode.