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Subject: Re: C optimization: int vs char

Author: Frank Phillips

Date: 11:23:46 10/15/01

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On October 15, 2001 at 05:56:20, David Blackman wrote:

>> I am predicting double the speed.
>>
>>Note that I am not talking about the KAP compiler for Linux (but rather) the
>>Intel C++ compiler 6.0 for Linux (which is now in beta).
>
>Double would be bloody amazing for chess code. I could understand it some kinds
>of floating point on the grounds that:
>
>1. Floating point on the X87 is really ugly
>2. Gcc doesn't try very hard
>3. If anyone can figure out how to make this mess go fast, it should be Intel.
>
>For the integer stuff, gcc is not great, but it's not all that bad either. It's
>mostly about half way between Borland and Microsoft, though occasionally it
>manages to beat both. I haven't heard anyone claim the Intel compiler is twice
>as good as that. I've spent a fair while staring at inside loops of various
>stuff generated by gcc, and in most cases, there is no way anything is going to
>go twice as fast on the same chip.
>
>That said, i will probably try to get hold of this if it isn't to huge.

After something of a struggle (my ISP automatically disconnects after two hours
and at less than 56k/s it takes longer) I finally got the Intel compiler down
and working.

I am impressed.  It is certainly not twice as fast but faster.  On my program
and the little fixed ply search test I do to check that I still get the same
number of nodes when they should not have changed, the comparison is:
gcc2.96        403knps
intel          467knps
(MSVC++        522knps)

The executable has increased in size to 830kB.  If I link it statically it goes
to 2.52MB.

The executables use Intel libraries, so you have to set up the environment
variables.  If anyone knows how to do this at boot, rather than through the
users.bashrc file, please let me know.

Anyway, thanks for the tip Dan.

Frank




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