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MathGroup Archive 1999

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Re: how long is a long evaluation?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19505] Re: how long is a long evaluation?
  • From: "David Bailey" <dave-bailey at freeuk.com>
  • Date: Sat, 28 Aug 1999 15:53:23 -0400
  • References: <7q2158$q9s@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

psalzman at landau.ucdavis.edu wrote in message <7q2158$q9s at smc.vnet.net>...
>dear all,
>
>i have a triple integral of a gaussian and a bunch of step functions of 4
>variables.  the expression is not that difficult, but it's not exactly 2+2
>either.
>
>last night i started Mathematica on it.  went to bed 4 hours later and when
i looked
>in the morning, it had reported "out of memory" (i have 96MB).
>
>next i tried doing the integral with only one of the step functions to see
>if that sped things up.  so far it's been 4 hours and Mathematica is still
plugging
>away.
>
>i'm beginning to suspect that the way i've entered the integral is wrong.
>i asked the department "mathematica guru" but he had no words of wisdom for
>me.
>
>1- is there a way of telling if Mathematica is still plugging away or is
just hung
>in some kind infinite loop?   can i see what Mathematica is working on at
any given
>moment?   what is a reasonable maximum time for a difficult symbolic triple
>integral?   has anyone had something like this that ran for more than 4
>hours?  (dual PII/266)
>
>2- would someone be kind enough to look at this notebook?  it's 4 cells
>long (so it's terribly short) and i'm sure if there's a mistake, it will be
>glaring to the trained eye.
>
>my *sincerest* thanks to anyone who can help.
>
>pete
>

Unfortunately there will always be computer algebra problems that generate a
combinatorial explosion when you try to run them. Yours may be of that type,
or there may be something that can be corrected.  I do not know if you sent
your notebook as an attachment, but it is not here with your message. I
suggest you post again with the text of your notebook appended to the
message. You can remove all the stuff before Notebook[
and all the stuff at the end about cache information.

David Bailey
Salford Software




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