Re: benchmarking (or almabench)

[Jeremy Sanders <jss@ast.cam.ac.uk>]

On Tue, 22 Apr 2003, Daniel Berlin wrote:

> On Tuesday, April 22, 2003, at 11:08  AM, S. Bosscher wrote:
>
> > -march=pentium4 is known to pessimise code compared to -march=i686 for
> > some
> > benchmarks, see PR 8474.  Maybe you're seeing the same problem?
>
> Actually, if i had to guess, i'd put my money on the vectorization.
> Notice ICC vectorized two loops in his example, and obviously, we
> vectorized 0.
> :)

The intel compiler doesn't seem to vectorize with just "-O2" (by default
it should report whether it is using vectorization), and that's still 88%
faster than gcc. I can't absolutely confirm there's no vectorization as I
can't see a switch to turn it off.

icc says it's vectorizing when the P4 specific options are enabled (which
gcc can't do yet).

If I turn off any optimization on icc, then it's still faster than gcc!!!

xpc5:/<3>almabench-1.0.1/cpp> make
icc -o almabench.o -O0 -c almabench.cpp
icc -o almabench -O0 almabench.o
xpc5:/<3>almabench-1.0.1/cpp> time ./almabench
23.853u 0.134s 0:25.82 92.8%	0+0k 0+0io 121pf+0w

Jeremy

-- 
Jeremy Sanders <jss@ast.cam.ac.uk>   http://www-xray.ast.cam.ac.uk/~jss/
X-Ray Group, Institute of Astronomy, University of Cambridge, UK.
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