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MathGroup Archive 2006

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"In progress" saving of data collected using Reap/Sow

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66081] "In progress" saving of data collected using Reap/Sow
  • From: giacomo.ciani at gmail.com
  • Date: Sat, 29 Apr 2006 03:40:11 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello to everyone,

I'm quite new to Mathematica, so please be patient if I ask something
trivial.
I wrote a little simulation program that need to iterate a calculation
thousand of times, storing the result of each iteration. At first, I
used the "Append" function to store data in a list at every iteration,
but I noticed that this operation become slower and slower as the list
increases in size, so that appending a single data at the end of a
quite big list takes a lot of time.
So I migrated to the reap/sow functions that are written exactly for
this purpose, ad gives much better performances. My code now is
something like:

results = Reap[Do[a lot of iterations with almost a call to Sow in
each]]];

The problem now is that, since the collected data are returned by the
Reap function only whern it terminates, I have no way to access that
data if the calculation is in progress, ie if the Do loop is not
completed. This way, I can't check the status of the calculation nor
provide backup save of data during the calculation itself, that can
last for days...
As you can imagine, using the Append function both this (and others)
tasks where easily accomplishable, since in every moment I had a list
whith all the results obtained so far...

Any idea on how I can solve the problem?

Thanks a lot

Giacomo


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