sgi® altix™ introduction to intel compilers · 2007. 2. 9. · sgi gmbh reiner@sgi.com | january...

January 19, 2005

SGI® Altix™Introduction to Intel Compilers

Reiner VogelsangSGI GmbH

reiner@sgi.com

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Objectives

• After completion you understand –some fundamental optimizations of the Intel compiler and–the informations of the optimizer report provided by the

compiler

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New command line switches

Run-time checking (-check)

Floating point exception handling (-fpe)

Non-native I/O conversion (-convert)

Detect FP stack corruption (-fpstkchk)

Display traceback on errors (-trace)

Link in threaded libraries (-threads)

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Compiler Directives

Fortran:cdir$ ivdep

cdir$ swp

cdir$ noswp

cdir$ loop count (NN)

cdir$ distribute point

cdir$ unroll (n)

cdir$ nounroll

cdir$ prefetch a

cdir$ noprefetch c

no aliasing

try to software-pipeline

disable software-pipelining

hint for SWP

split this large loop

unroll n times

do not unroll

prefetch array “a”

do not prefetch array “c”

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Compiler Directives

C/C++:#pragma ivdep

#pragma swp

#pragma noswp

#pragma loop count (NN)

#pragma distribute point

#pragma unroll (n)

#pragma nounroll

#pragma prefetch a

#pragma noprefetch c

no aliasing

try to software-pipeline

disable software-pipelining

hint for SWP

split this large loop

unroll n times

do not unroll

prefetch array “a”

do not prefetch array “c”

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