gurobi 'Missing constraint index'

"Missing constraint index" error in Gurobi usually occurs when you are trying to modify or delete a constraint that does not exist in the model. This error can also occur if you are trying to add a new constraint with an index that already exists.

To resolve this error, you can try the following steps:

1. Check if the constraint index you are trying to modify or delete actually exists in the model. You can use the getConstrs() method to get a list of all the constraints in the model and their indices.

2. If you are trying to add a new constraint, make sure that the constraint index you are using does not already exist in the model. You can use the same getConstrs() method to check for existing constraint indices.

3. Check if you have any typos or errors in the constraint index you are using. Make sure that the index is a valid integer and that it matches the format of the other constraint indices in the model.

4. If none of the above steps work, try resetting the model and adding all the constraints again from scratch.

I hope this helps you resolve the "Missing constraint index" error in Gurobi.