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Re: [OT] GCC vs Intel C++ compiler benchmark


On Sunday 27 January 2002 03:48, Claus Fischer wrote:
> The rather biased article on http://www.open-mag.com/754088105111.htm
> compares Intel's C++ favourably to GCC, without disclosing many
> enlightening details.
>
> I'm not concerned with that but with the notable OS difference
> between Linux (SuSE 7.3) and Windows (XP Pro). IMHO a CPU bound
> benchmark should see less than 1 % influence from OS and C library.
> The graphics shows roughly 7% better performance on Windows for the
> same (Intel) compiler.
Both gcc and icc (beta versions available to customers) have improved 
significantly since then.
>
> Are there any ABI differences which would justify such a difference?
> Register use conventions? Other stuff that you could identify?
glibc vs Windows libraries; greater maturity of the Windows version under 
test; different default compiler options
>
> Unfortunately the benchmark gives no details about compiler options,
> so presumably the answer is `the benchmark is flawed' and `go ask
> them'. In this case don't bother to answer.
Probably many of the comparisons are deficient in matching compiler options
gcc				icc			icl
-fstrict-aliasing (default on) 	-ansi (default off)		-Qansi (default off)
according to data type		-pc64 (default 80)	pc64, no choice
-march=pentiumpro		-tpp6			-G6
-march=pentium4 (gcc-3.1)	-tpp7			-G7
-msse2	(gcc-3.1)		-xW			-QxW

and the default for the Intel compilers resembles
 gcc -ffast-math -Os -funroll-loops -mpreferred-stack-boundary=4
to mention only a few of the simpler comparisons which will affect performance

>
> Claus


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