Error Messages/9351

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Revision as of 18:40, 16 June 2010 by Lchrisman (talk | contribs) (Guidance for what to do)

Solver Error

SolverSDK: Unexpected error. Please contact Technical Support.

Cause

This error indicates the presence of a bug inside the Solver engine. If you see it, please let us know by providing an example (such as your Analytica model) and steps to reproduce it. You can report this bug to Lumina Technical Support support@lumina.com and we will interact with Frontline Systems' engineering team to fix.

Since it is an internal bug, there isn't any information in the error message alone to give a clue as to what might factor might be tripping up the solver. If they knew what caused this error in this particular case, they'd have fixed it. But since the solver solves the vast majority of problems without encountering this error, we can assume there is some property of your formulation that is somewhat unusual. Perhaps:

  • Maybe it pushes the bounds of available memory, and an out-of-memory condition wasn't handled gracefully?
  • Maybe your problem involves NaN, Null, or INF values that might trip it up?
  • Maybe you have some unusual search parameter settings (i.e., the «Parameter» and «Settings» parameters to DefineOptimization, LpDefine, NlpDefine or QpDefine).
  • Maybe your quadratic constraints have a singularity?


Remedies

First, make sure you are using the latest Analytica release, so that if the underlying problem has previously been identified and fixed, you will have the fix. Go to the Analytica Download Page to check what the most recent release is.

The problem might be specific to a particular solver engine, so changing engines might make it go away. For a non-linear problem, you might be able to change from the "GRG Engine" to the "Evolutionary" engine. For a linear or quadratic, you might be able to changed from the "LP/Quadratic" engine to the "SOCP Barrier" engine, or for a LP, QP or quadratically constrained QP, you could try changing to "GRG Nonlinear". There are also numerous add-on engines also available. To change the engine, specify the engine name in the «Engine» parameter.

Next, you would want to see if you can identify something unusual about your formulation. For an LP or QP, examine all the input parameters carefully. Look for any INF, NaN or Null values, or other extremes that might be unusual.

For a non-linear problem, add the «traceFile» parameter (specify a filename) and try solving it. Then pull the trace file up in a text editor and examine the sequence of steps that the solver explored. Sometimes you can see something unexpected happening -- the solution going off in a strange direction. Maybe that led the solver into a spot where it got tripped up. It might expose a problem in your formulation, so that if you correct that, it'll avoid this internal error.

Try changing integer decisions to continous and see if it makes a difference. Unset unusual parameter settings.

If you do manage to find a workaround in your case, you should still report this to support@lumina.com, who will look at it and forward bug reports to Frontline if necessary. This way, the underlying cause can be identified and fixed for future releases.



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