Re: Calculation mystery

From:
"Doug Harrison [MVP]" <dsh@mvps.org>
Newsgroups:
microsoft.public.vc.mfc
Date:
Sat, 17 May 2008 16:14:00 -0500
Message-ID:
<p8iu249f6sglbneupdfe2ia7mr80c158b3@4ax.com>
On Thu, 15 May 2008 13:08:00 +0100, Stephen Wolstenholme
<steve@tropheus.demon.co.uk> wrote:

I have problem with calculations in a program produced using VC++ and
MFC. The calculation is using double floats. It loops until the result
is reduced to a target value.

In debug mode the calculation needs 178 loops. In release mode the
calculation is not consistent and sometimes needs over 38000 loops.


On Sat, 17 May 2008 18:05:26 +0100, Stephen Wolstenholme
<steve@tropheus.demon.co.uk> wrote:

The threads read a link list. The results are written to four
different lists that are merged when the calculating has finished. The
four threads are to take advantage of multi's. However, I am testing
on a single core machine to keep things simple.


Is it possible to define the subset of the problem each thread will solve,
such that run-to-run, the results are reproducible? This could help you
discover concurrency problems, and it could help you further understand the
nature of the discrepancy between debug and release.

--
Doug Harrison
Visual C++ MVP

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