Newsgroups: comp.os.msdos.djgpp
Subject: large variation in run-time
Message-ID: <354DAFD3.8D277F06@CPRO.DLO.NL>
From: Johan van Ooijen <J DOT W DOT vanOOIJEN AT CPRO DOT DLO DOT NL>
Date: Mon, 04 May 1998 13:08:51 +0100
Reply-To: J DOT W DOT vanOOIJEN AT CPRO DOT DLO DOT NL
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To: djgpp AT delorie DOT com
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Hi,
I am performing Monte Carlo simulation studies that require millions of
runs. In order to predict how long each session is going to take I use
trial sessions of 1000 runs. I find that it not possible to predict the
duration of 10^6 runs. For instance, two sessions I predict to take 34
and 68 hours, respectively (one should be exactly twice as long as the
other), and they took 10 and 43 hours. It is fine that the sessions take
shorter, but it is strange that the second is not even close to taking
twice as long as the other. So this leaves me with the uncertain feeling
of the correctness of the results, although they appear to be what I
expect.

So the question is, whether there is an explanation for these large
variations in run-time when using go32 ?

The software is pure ANSI C, no warnings are given by the compiler (gcc)
whatsoever. The program uses little memory, it does millions of
malloc()'s and free()'s, but total used memory doesn't grow (so that is
OK) and there is no swapping activity.
I run under MSDOS 6.22, with 
   device=himem.sys
   device=emm386.exe ram x=d800-dfff
   dos=high,umb
and go32 says:
   go32 version 1.12.maint3
   ...
   VCPI (Expanded) memory available: 29312 Kb
   Swap space available: 131040 Kb

Any help is appreciated. Please also mail me directly:
   j DOT w DOT vanooijen AT CPRO DOT DLO DOT NL

Thanks,
Johan van Ooijen