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Date: Sat, 05 Sep 1998 02:30:19 +0000
To: strasbur AT chkw386 DOT ch DOT pwr DOT wroc DOT pl (Krzysztof Strasburger),
        beastium-list AT Desk DOT nl
From: Vincent Diepeveen <diep AT xs4all DOT nl>
Subject: Re: pgcc and your remarks
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At 04:37 PM 9/4/98, you wrote:
>Vincent, I can't reach you via private mail!
>I'm sorry for sending this to the list.
>>|------------------------- Failed addresses follow: ---------------------|
>> diep AT xs4all DOT nl ... transport smtp: 571 <diep AT xs4all DOT nl>... You can't use
this mailserver as a relay for this address.
>>Subject: Re: pgcc-1.1a - first impression
>
>>What about using MSVC and programming stuff somewhat better?
>>Then you only need to wait for a few months.
>MSVC? No, thanks. Do you have MSVC for something other than Windows or DOS?
>Could you imagine Windows machine running flawlessly for few months? Running
>a cluster of Windows machines flawlessly?
>Let us stop the discussion at this point. I don't have MSVC and won't buy
>or even steal one.
>And the program is mixed FORTRAN and C code (trivial, if you have f2c).
>It went already through many improvement iterations. This is not
>the right place for discussion about it. There are problems in computational
>quantum chemistry/physics, which cannot be done in an hour.

I ran 2 weeks with msvc at NT sp3. Memory leak in sp3 is fixed.

>>The reason that those bizarre optimizations like -fno-runtime-lift-stores
>>are faster is only because the program is not written very well.
>Not _faster_, but _reliable_. This option gives _bad_ code.
>Krzysztof

Wow, that's weird. Why need it? Another problem in (p)gcc?

I've tried all gcc compilers and almost all options available.
NOT A SINGLE OPTION gives better code than -O2

Same for MSVC.
NOT A SINGLE OPTION in msvc gives better code than the -O2

I'm using Watcom c++ for the DOS version

in watcom c++ all options except for the normal pentium and optimiztion
option hardly make difference. It doesn't get it a single percent faster.

In the past this did made difference.

Code of chessprograms is among the best checked and best
programmed code in the world, no doubt about that.

I've rewritten and tested nearly every line 100 times. No kidding.
Some parts probably even more. 

Yet hard to see is where the difference in speed is between the
compilers. Loops are so well written that both gcc and msvc optimize it
equally well. Not an instruction i would be able to spare when thinking as a 
compiler. Easy to code patterns too.

The main problem for my program is that the btb cannot be used too much.
I'm having thousands of patterns (if then else), so a good optimization
of 'if then else' gives more than anything else.

At a certain point i would guess compilers cannot optimize better anymore,
without using the special pro/PII non-mmx-instruction set.

Most of the loops in DIEP have been checked. Both GCC and MSVC perform equally
well. So the only diff is in the pattern optimization.

Yet that gives already 10% extra speed.