[SCIP] Too long solving time

[Yu Chen]

Hi Matthias

Thanks for your help!

Currently I cannot change my model.

Besides, the reason why I enforced 1e-10 is that I got another problem before. At that time, the feasible solution was actually not constrained by my model. For example there was an equation ‘x+y=0’, but the solution showed ‘x=1e-6’ and ‘y=0’, and I was suggested to use very low tolerance and then I got like ‘x=1e-6’ ‘y=-1e-6’.

Considering this, do you think I can adjust some parameters to save time when running SoPlex instead of changing the model?

Best regards
Yu

Sent from my phone. Excuse the brevity.



On Fri, Aug 17, 2018 at 12:00 PM +0200, "Matthias Miltenberger" <miltenberger at zib.de<mailto:miltenberger at zib.de>> wrote:

Dear Yu Chen,

your model has some numerical issues. The matrix coefficients are in the of 1e-05 to 1e+11. Such a large range can easily cause difficulties and violations in the final result.
To make matters worse, you are disabling presolving/simplification (-s0) and enforce very small tolerances (1e-10).

Testing other solvers on this instances also yielded warnings and violations due to the bad numerics.

My advice: Try to improve the model and verify that your result is actually meaningful with regards to the problem. I don't think that such a small tolerance is really required.

Oh and by the way: On my machine the model was solved within a second using the standard tolerances and default settings.

Cheers
Matthias

On 17.08.2018 10:59, Yu Chen wrote:
Hi,

I am new to Soplex but I encountered a trouble when using it.

I made a LP file and used the code in terminal:


/build/bin/soplex -f1e-10 -o1e-10 -l1e-10 -s0 -x -q -c

But the Soplex took nearly one day to solve it. Do you know how to decrease the solving time?

Best regards,
Yu



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Matthias Miltenberger
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