Troubleshooting Guide for Error -100180

If you're seeing a score of "-100180" (that's a negative number) for one of your generated schedules, it means that the scheduling engine is working to ensure that sessions don't interrupt other sessions.

If the scheduler completed with this error code (i.e. you see the text "Did not find any solutions" in the Stage column), then this article describes the next steps you should take.  (For background, you may also want to check out Why didn't the engine find any results?.)

If the scheduler is still running (i.e. you see the text "Solving (4 of 6)" in the Stage column), and it's been stuck on this error code for a while (i.e. over an hour), you might want to take corrective action right now. There's a small chance that your caseload will still produce viable schedules before the end of its computation window, but it's not looking good. This article describes the next steps you should take.

Resolve Conflicting Constraints

If your caseload has any conflicting constraints, those must be resolved before the scheduler will succeed. In other words, the scheduler can only find a solution if the puzzle pieces you give it somehow fit together.  More info.

Generally, conflicting constraints are caused by mistakes while entering the caseload data.  Check back over your caseload configuration, and ensure that there are no conflicting pieces of information.

Here are some common conflicts that you might want to look for in your caseload:

  • Double-check the "Class Periods" for any entry mistakes
  • Double-check the "Building" value for every student in your caseload for any entry mistakes
  • Double-check the "Grade" value for every student in your caseload for any entry mistakes
  • Double-check the "Exact Time Spans" for every student session in your caseload for any entry mistakes

If you find any of these conflicts, simply remove the conflict and try scheduling again.  While you're editing your caseload, also look for additional instances of that same conflict.

Reduce "Hard" Constraints

If your caseload has too many "hard" constraints, then it will severely slow down the scheduler. In fact, it may slow down so much that it will take weeks or months for the supercomputers to find a solution.  More info.

If this is happening to you, you may either:

  • Remove the "hard" constraints altogether
  • Replace the "hard" constraints with "soft" constraints.  More info.

Generally speaking, please reconsider any self-imposed constraints. Some of your constraints come from your state's laws, or from policies that your administration has put in place. If any of the constraints you've entered are really your own preferences, try removing them. The scheduler works best when the only hard constraints are the ones that are absolutely necessary.

Here are some suggestions for your caseload:

  • Remove exact time spans from students in your caseload
  • Don't schedule your sessions in alignment with class periods
  • Remove any non-critical "Must Not" entries for every student in your caseload, or convert them to "Prefer Not" entries

The easiest way to do some of these things is to use one of the following "Caseload Transformations" on your caseload page:

  • Remove exact time spans
  • Convert student "Must Not" entries
  • Do all reversible transformations
  • The Nuclear Option

However, you can also make manual changes to your caseload to make the updates yourself.

After removing or replacing some/all of your hard constraints, try scheduling again.

Last Resort

If you have an unusually large caseload, or relatively few days to see all of your students, the scheduling engine may not have enough available therapy time to squeeze everything in.  More info.

Before applying the last resort, you should first try the above suggestions:

  • Resolve all of your conflicting constraints
  • Remove/replace all of your "hard" constraints

If you've already done these things, and are still having trouble, please follow the generic instructions here under "Caseload Is Too Large".

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Historical notes:

  • In previous versions of the scheduler, this was covered by error -100008 or -100245.

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