Retrieving MVar from Model read from file
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After loading a Gurobi model from file (e.g. m = gp.read('my_model.mps')), I am unable to retrieve matrix variables.
For example, if the model had MVar with name "X" when it was previously constructed and saved, reloading the model and doing m.getVars() will return a list of every scalar entry in X (and all other matrix variables), and m.getVarByName("X") returns None.
How can I retrieve my MVars?
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Apparently it is a new feature, but it would be really nice to be able to retrieve them as a matrix.
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Unfortunately, this is not how gurobipy and Gurobi work. The Python API in gurobipy is, by design, just a layer around the C API of Gurobi. And the C API does not understand the concept of matrix variables. The writing and reading of model files happens on the C layer. Hence, the structure of matrix variables is not contained in the *.mps files.
Regards,
Tobias
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I have come across the same issue. What works well for me is creating a model with the same variables (MVars), then reading the values to model from the *.sol file.
In Python:
model = gb.Model()
var = model.addMVar((correct, dimensions), name="var")
model.update() # prepare the variables to be accessible to read
model.read("solution.sol") # load up the values
model.optimize() # without constraints, this is almost instant
print(val.X) # val.X can now be accessed0 -
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