How to modify variables and constraints of an existing CP-model

[Devarshi Raval]

Hey!

I have written a CP model in Python, which uses CP-SAT solver. I need to run that model multiple times, and in each run I modify constraints. Currently, I create the model object from scratch, every time I want to run the model. Is there anyway, I can modify variables/constraints of an existing model, so that I don't need to build the model from scratch every time?

To give better context, please consider the below sample model.

from ortools.sat.python import cp_model

model = cp_model.CpModel()

num_vals = 3

a = model.NewIntVar(0, num_vals -1, 'a')

b = model.NewIntVar(0, num_vals -1, 'b')

c = model.NewIntVar(0, num_vals -1, 'c')

model.Add(a == b)

solver = cp_model.CpSolver()

solver.Solve(model)

Now, in the 2nd run of the problem, I want to do following changes.

1. Change the upper bound of variable c to 5
2. Delete the constraint a==b
3. Create a new constraint a==c

How can this be achieved without building the model from scratch?

[Xiang Chen]

X-Post: https://stackoverflow.com/questions/68207910/how-to-modify-variables-and-constraints-of-an-existing-google-or-tools-constrain

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