That being said, very recently, python-mip was released and it supports both removing variables and constraints and has c-bindings. # change the bounds on constr2 to recycle it and add new variables If you wanted to add a new constraints, you can So in your code example, to rerun without creating an new model from scratch you need to do: (.)Ĭonstr2.SetBounds(-solver.infinity(), solver.infinity()) I heavily suspect that I get floating points noise in the recycling but it's stable enough in practice for my needs. In my wrapper, I would keep a list of deactivated constraints/variables and recycle them instead of creating new ones (which was proven to lead to both increased runtimes and memory leaks because C++ + python is a nightmare in those areas). To deactivate a variable or a constraint, I would set coefficients to zero and free bounds (set to +/- infinity) and set costs to zero to effectively deactivate the constraint. So to answer your question: to 'remove' variables or constraints with or-tools, I had to build my own python wrapper around or-tools. So if I remember correctly, only pylp and or-tools had c bindings and again if I remember correctly, pylp was NOT python 3 compatible (and has been in limbo ever since) so I settled on or-tools. It is unscalable due to the overhead of writing and reading files on disk. I absolutely needed that feature for my tech stack and tried multiple python linear programming librairies out there (wrappers around clp/cbc really) and I settle on or-tools despite that flaw for 2 main reasons 1) this was the only librairy with the minimal features support I required out of the box and 2) at the time (~4-5 years ago) it was the only librairy using C bindings.Īll others used one form of another of interfacing with the cbc command line which is a. Some words about ProjectLibre costing features: For each resource you can define: Effective date: From when do the following rates are valid Standard rate: Rate per hour for normal working hours Overtime rate: Rate per hour for overtime working hours Cost per use: Cost for resource usage independent of duration. From an engineering perspective, messing with the internal logic to remove them 'by hand' is dangerous. In this semi code the number of constraints were limited but actually, in my real code the number of constraint are many and I can not define them from first.Īs far as I know, or-tools does not provide any interface that removes constraints or variables. Now in the second time of running my code I want to remove constraint number 2, but I can not find any operation to do it and the only way is to clear solver and define constraint from first. New and updated version of OpenProj with hundreds of updates/bug fixes. Variable = solver.IntVar(0, 20, variable 2 )Ĭonstraints.append(solver.Constraint(8,10))Ĭonstraints.SetCoefficient(variable,1)Ĭonstraints.append(solver.Constraint(5,10)) Variable = solver.IntVar(0, 10, variable 1 ) Variable = solver.IntVar(0, 5, variable 0 ) Solver = pywraplp.Solver('SolveIntegerProblem', Suppose my problem is to maximize sum of 3 variables which two constraintsĬonstraint1: variable 2 should be between 8 - 10Ĭonstraint2: variable 3 should be between 5 - 10 from ortools.linear_solver import pywraplp Is there any way to remove defined constraint from solver with out clearing solver and creating constraints from first?
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