Intel and GNU C++ compilers

José M. Pérez Sánchez iosephus at
Mon Oct 13 09:38:36 EDT 2003


I just wanna thank everybody for the responses to my last question about
Intel compiler, I tried both 'gcc' and 'icc', and got the following results
for one of our work files containing 10^6 steps of calculation:

*** gcc version 2.95.4 ***
flags                bin-size   elapsed-time
-----                --------   ------------
none                 9.5 KB     311 sec
"-O3"                8.7 KB     192 sec
"-O3 -ffast-math"    8.7 KB     165 sec

*** icc version 7.1 ***
flags                                    bin-size   elapsed-time
-----                                    --------   ------------
none                                     597 KB     100 sec
"-O2 -tpp7 -xW -D_IOSTREAM_OP_LOCKS=0"   563 KB      89 sec

the flags -tpp7 and -xW in 'icc' activate Pentium4 and SSE2 extensions
respectively, I guess that using a newer 'gcc', capable of '-march=pentium4'
and SSE2 extensions would improve 'gcc' results.

I am running on a Dual Xeon 2.4 Ghz machine, with 2Gb of RAM. I use
Debian Woody with a 2.4.22 kernel compiled by myself. HyperThreading
is disabled at the BIOS level.

The test were run on one processor only.


Jose M. Perez.
Madrid, Spain.

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