Author: Vincent Diepeveen
Date: 08:21:40 12/20/02
Go up one level in this thread
On December 19, 2002 at 13:16:02, Frank Sgarra wrote:
After that diep gave away a pawn with the intel c++ compiler
and not with any other compiler (also giving difference in score
for mainlines), i started checking out that intel compiler
more.
I found several bugs in intel c++.
One of them i posted here at CCC some time ago for version 6.0 of
intel c++.
it was something in factorization code to see whether there
is a coefficient somewhere. something like:
int lineaircoefficient(int a,int b) {
float a,b,c;
(formula)
a = ..
b = ..
c = ..
return((int)(a*b+c));
}
There was a big bug in the:
return((int)(a*b+c));
It is not my work to detect bugs in the intel c++ compiler, which
is a fulltime work i bet.
Just compile any non-specint software and see what happens with it.
A good example is to compile some linux stuff with gcc.
Perhaps the gcc compiler itself would be a good example. Please compile
it with intel c++ and you'll see yourself zillions of examples.
Then you first find out whether it's a bug in the software secondly
you try to find out whether it's a compiler bug.
I am not big compiler expert but i even understood what a compiler
expert wrote at a homepage somewhere.
Most compilers are single pass compilers.
the intel c++ compiler is not.
advantage: they can use more optimizations than other compilers especially
for specint that is very useful.
disadvantage: it is a more buggy approach.
also in past (especially 5 versoins) i used to get a lot of internal
intel compiler errors.
I hope you realize that compilers and testing them is going to be
a fulltime job and i for sure am only going to do that when i get
paid for it.
Until then i will skip taking a good look to intel c++.
Additionally i own AMD machines which are faster than the intel machines
i own. Intel is of course not doing effort to be fast on AMD machines.
In contradiction. It's trivial that if version 5.0 is not doing bad for
AMD K7 processors, that when version 6 is doing a lot better for P4,
and a lot worse for K7, that version 7 and 8 aren't going to perform
better.
Even a default compile with a compiler from years ago (msvc6 sp4 procpack)
is already a lot faster on any K7 than intel c++ 6.0 is.
The major problem i have with intel c++ is simply that i cannot trust it.
You can only trust on it that specint and specfp programs run well with it.
Crafty is a good example.
Best regards,
Vincent
>On December 19, 2002 at 12:59:05, Vincent Diepeveen wrote:
>
>>On December 19, 2002 at 11:40:14, Frank Sgarra wrote:
>>
>>use intel c++ at own risk.
>>
>>never use it for code that is very critical for your company.
>>never use it for a version of your chess program that joins
>>a tournament.
>>
>>you'll give away a piece (or pawn in case of diep) because of
>>bugs in a new intel c++ version. Let me assure you that.
>>
>>DIEP did.
>
>
>
>i would be happy to have a pice (my own) of code
>that produces wrong(different) outputs compiled with intel C++,
>because maybe it would give me a pointer to a buggy place in
>my own program.
>
>can you repeat the wrong output of diep when using that compiler?
>
>did you prove, that intel C++ is doing a bad job ?
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