Reuse variables in CP-SAT solver

[Yuehan Li]

Hi,

Is it possible to reset Boolean variables once they have been solved?

We have a lot of Boolean variables associated with a large dataset and use CP-SAT solver to determine their values .A small portion of the dataset undergoes frequent modifications.  Instead of rebuild the model each time, is it possible to reset and reuse the Boolean variables and solve them?

[Frederic Didier]

The input to CP-SAT is a CpModel proto, there is no issue modifying this in place between solves.

But the gain will be minimal since the solver will still rescan the whole proto and restart from scratch each time.

If the code to create a model is slow, then this can be beneficial though.

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[Yuehan Li]

Yes, the creation of the model is slow. How do I modify the variables so that I can reuse them ?

[grego...@gmail.com]

Is it possible that large part without modifications doesn't need to be modeled completely ? I model a problem also with constraint solver. After initial propagation I have limited domains of variables, this information is very useful for cp-sat model since I can skip some parts of a model without feasible solution.

[Laurent Perron]

Solve is stateless. So I guess the answer is no. 

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[watchdogs132]

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