On Thu, 02 Nov 2000, you wrote:
> Hi,
>
> I have got a problem: I have tried to run old large Fortran code
> (compiled with fort -fast) and have noticed that it is unexpectedly slow.
> Closer investigation revealed that it spends more than 50% of CPU time in
> kernel. I suspect that the program does some kind of ugly floating point
> operations that require kernel support. The final numbers appear to be
> correct (compared against other architecture).
>
> Does anybody has ANY advice how to approach this problem? Is there any
> way to find out the offending part of code? I thought I could run gprof
> but I am not sure it show up in the output time spent in kernel..
Probably the kernel needs to be recompiled with the "kernel FP
software completion" set to "yes". This item is is the kernel hacking menu-
the last menu when you run "make xconfig".
Also, have you tried compiling your code using the following flags:
-fpe0 -synchronous_exceptions -arch host -tune host
Good luck,
Nikos
-- Dr. Nikolaos A. Margaritis Molecular Modelling of Materials Laboratory Department of Physical Chemistry National Centre for Scientific Research "Demokritos" Ag. Paraskevi, Athens 15310, Greece. Tel.: +30(0)1 650 3960, +30(0)944 773242 (mobile) Fax.: +30(0)1 651 1766 URL: http://mmml.chem.demokritos.gr/~nmargar --------------------------------------------------------- So, if anybody wants to have hardware sent to them; don't call me, but instead write your own operating system. It has worked every time for me.Linus Torvalds
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