ICC performance gain

testi · 2008-11-19, 19:06

Hello, just out of interest i compared msieve performance when compiled with ICC and gcc 4.3.

Hardware :
model name : Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz
ram : DD2 8500

Software:
gcc (Debian 4.3.2-1) 4.3.2
icc (ICC) 11.0 20080930

Flags :
gcc : -O3 -fomit-frame-pointer -march=core2 -D_FILE_OFFSET_BITS=64
icc : -fast -fp-model precise -D_FILE_OFFSET_BITS=64

GMP was used, compiled with gcc (I could'nt get it to compile with ICC before giving up)

Number to be factored (random 100 digits number generated with openssl):
1802716097522165018257858828415111497060066282677325501816640492782221110851604465066510547671104729

I tried to be as fair as possible and copied the factor base from the first run (gcc) for the icc run and fixed the random number in the source.

Results :
GCC :

Code:

Mon Nov 17 03:29:59 2008  prp50 factor: 38589340584901213653958931179714585367490014795273
Mon Nov 17 03:29:59 2008  prp50 factor: 46715390058453362424711065024780497160328505582673
Mon Nov 17 03:29:59 2008  elapsed time 31:46:11

ICC:

Code:

Tue Nov 18 13:39:01 2008  prp50 factor: 38589340584901213653958931179714585367490014795273
Tue Nov 18 13:39:01 2008  prp50 factor: 46715390058453362424711065024780497160328505582673
Tue Nov 18 13:39:01 2008  elapsed time 27:00:43

Full logs are attached

jasonp · 2008-11-19, 21:28

Thanks, that's good to know. Brian Gladman has kindly performed a complete overhaul of the preprocessor defines for compiler-specific inline asm, so that the next version will allow icc to reuse all the gcc-specific assembly language. I suspect that it currently does not.

Was this a 64-bit or 32-bit binary?

testi · 2008-11-19, 22:45

64 bits.
Do you mean msieve will use gcc intrinsics ?

I have seen with other programs that ICC register allocator and optimisations are dramatically more efficient than gcc (for SSE2)

jasonp · 2008-11-19, 23:41

I meant using gcc-format inline asm statements, which according to Brian can be parsed by icc. He also reports favorable speedups on windows.

testi · 2008-11-19, 23:46

maybe it would be worth trying intrinsics, i'll try to check if I have time

jasonp · 2008-11-20, 03:00

Actually, Intel's compiler could probably benefit from a prefetch intrinsic. The code has gcc and MSVC versions but no icc version in include/util.h

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Attempted User Privilege Gain	TObject	Forum Feedback	2	2015-02-27 17:25
64 bit performance?	zacariaz	Hardware	1	2007-05-10 13:08
no speed gain in Prime95's benchmark when overclocking	forcemaker	Hardware	8	2006-04-02 15:18
LLR performance on k and n	robert44444uk	15k Search	1	2006-02-09 01:43
5% performance gain running NFSNET + PRIME on a P 4 HT	TauCeti	Hardware	1	2003-07-02 22:22

2008-11-19, 21:28	#2
jasonp Tribal Bullet Oct 2004 3,541 Posts	Thanks, that's good to know. Brian Gladman has kindly performed a complete overhaul of the preprocessor defines for compiler-specific inline asm, so that the next version will allow icc to reuse all the gcc-specific assembly language. I suspect that it currently does not. Was this a 64-bit or 32-bit binary?

2008-11-19, 22:45	#3
testi Nov 2008 3 Posts	64 bits. Do you mean msieve will use gcc intrinsics ? I have seen with other programs that ICC register allocator and optimisations are dramatically more efficient than gcc (for SSE2)

2008-11-19, 23:41	#4
jasonp Tribal Bullet Oct 2004 110111010101₂ Posts	I meant using gcc-format inline asm statements, which according to Brian can be parsed by icc. He also reports favorable speedups on windows.

2008-11-19, 23:46	#5
testi Nov 2008 3 Posts	maybe it would be worth trying intrinsics, i'll try to check if I have time

2008-11-20, 03:00	#6
jasonp Tribal Bullet Oct 2004 3541₁₀ Posts	Actually, Intel's compiler could probably benefit from a prefetch intrinsic. The code has gcc and MSVC versions but no icc version in include/util.h