Mail Archives: djgpp/1998/05/07/04:31:14
Eli Zaretski wrote:
>On Mon, 4 May 1998, Johan van Ooijen wrote:
>
>> So the question is, whether there is an explanation for these large
>> variations in run-time when using go32 ?
>
>Does the program use disk I/O significant proportion of its run time?
No, once every millions of iterations a 100 lines are written to a file and
one line to the screen.
>Does it swap to disk? If so, your disk cache can skew the run time a
>great deal.
I don't see swapping activity. Memory allocated before the iterations is
less than 100 Kb, in the iterations about 1 Kb is malloc()'ed and free()'ed
each time. Total memory allocated doesn't grow. There's sufficient megabytes
of free memory.
>Another possibility might be the size of your innermost loop: if it
>sometimes overflows the CPU caches, you will see a factor of 2-4 in
>performance without any apparent explanation.
How does this happen?
>> and go32 says:
> > go32 version 1.12.maint3
>
>Huh? Is this program compiled with DJGPP v1.12? If it's v2.01, run
>go32-v2, not go32 (it's a completely different program, and reports
>completely different results).
Yes, I still use go32 version 1.12 and gcc version 2.6.0. It works great for
me (except for this strange phenomenon...). I'll go over to go32-v2 some
time...
By the way, I also ran these simulations on an Alpha under OpenVMS using
dec-cc and there everything runs as expected.
Johan van Ooijen
j DOT w DOT vanooijen AT cpro DOT dlo DOT nl
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