Parallel Computing Explained Porting Issues. Slides Prepared from the CI-Tutor Courses at NCSA http://ci-tutor.ncsa.uiuc.edu/ By S. Masoud Sadjadi School of Computing and Information Sciences Florida International University March 2009. Agenda. 1 Parallel Computing Overview
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Parallel Computing ExplainedPorting Issues
Slides Prepared from the CI-Tutor Courses at NCSA
S. Masoud Sadjadi
School of Computing and Information Sciences
Florida International University
1 Parallel Computing Overview
2 How to Parallelize a Code
3 Porting Issues
3.2 Word Length
3.3 Compiler Options for Debugging
3.4 Standards Violations
3.5 IEEE Arithmetic Differences
3.6 Math Library Differences
3.7 Compute Order Related Differences
3.8 Optimization Level Too High
3.9 Diagnostic Listings
3.10 Further Information
f90 -OPT:IEEEarithmetic=n ... prog.f where n is 1, 2, or 3.
f90 -c -O0 prog1.f
f90 -c -O3 prog2.f
f90 prog1.o prog2.o
a.out > results
f90 -c -O0 prog1a.f
f90 -c -O3 prog1b.f
f90 prog1a.o prog1b.o prog2.o
a.out > results
f90 -listing ...
f90 -fullwarn ...
f90 -showdefaults ...
f90 -version ...
f90 -help ...
-On where n ranges from 0 to 3.
-O0 turns off all optimizations.
-O1 and -O2 do beneficial optimizations that will not effect the accuracy of results.
-O3 specifies the most aggressive optimizations. It takes the most compile time, may produce changes in accuracy, and turns on software pipelining.
-Ofast = ip27
is also available. This option specifies the most aggressive optimizations that are specifically tuned for the Origin2000 computer.