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[MUG] Re: Stopping integration due to what?
| [MUG] Re: Stopping integration due to what? |
|
Author: Allan Wittkopf
Posted: 27/11/2000 23:00:51 GMT
|
>> From: Allan Wittkopf
By default, DEplot uses a fixed step method to integrate the input system.
There could be a number of reasons for the failure.
1) The problem could be too difficult for a fixed step method (there are regions
that need a very small step size).
2) The problem could be stiff
One of the options for DEplot is 'method=<your method of choice>'.
The first thing I would suggest is using method=rkf45 - a variable step
integrator.
If this does not work, then I suggest trying method=lsode - a stiff integrator.
In any event, the message being returned to you is not helpful, and requires a
fix.
Would it be possible for you to post the actual system that is giving you the
problem so I could try it out?
Thanks,
Allan Wittkopf
| >> From:
|
| In running my model (7 ODEs) using DEplot, I sometimes get the error message
| "Stopping integration due to, undefined", depending on the parameter values
| used. In some cases, decreasing the stepsize gives indeed the desired plot.
| COULD the size of the stepsize BE the reason for the error message?
|
| In other cases I have to decrease the stepsize so much that my computer
| crashes (no simulation succeeded for stepsize=0.0001 and t=0..500). My
| computer is a Pentium 794MHz, 128 Mb RAM. Is it possible to write the points
| that are calculated by DEplot to a file, such that after each time step the
| value for each variable is written to a file? If the computer gets stuck in a
| particular run, then at least the points until the crash are available, which
| may provide information on the cause of the crash.
|
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