When does gurobipy call C code?

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Samuel Mallick

• 2024年04月17日 12:34

I am wondering at which point in the execution of a python program, using gurobipy, does C code get called?

Is it at the point where the model is created, i.e., m = gp.Model()?

Or is it when the model is optimized, i.e., m.optimize()?

Additionally, is the C code that is called compiled/object code? Finally, does the execution return to the python program at any point during the solving, or does everything happen in C code until the solution is returned to the python program?

Thank you,

Samuel

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  Simon Bowly

  Gurobi Staff

  • 2024年04月29日 09:09

  Hi Samuel,

  gurobipy is tightly integrated with the Gurobi C API, so C code is called any time you make a gurobipy API call. For example:

  1. gp.Model(...) calls the C API to construct a model
  2. x = model.addVar() calls the C API to add a variable to a model
  3. model.addConstr(x + y <= 1) calls the C API to add a constraint (though the expression arithmetic is done on the python side)

  All C code that is called here is compiled: gurobipy itself is a compiled extension module, which is linked to the compiled Gurobi library.

  Execution does return back to Python during solving in a few cases. One case is logging: log messages from the solver are routed back to Python's logging module and output streams. Another case is callbacks: if you provide a callback function, execution returns to your Python code on every callback invocation.

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