how to provide an initial solution in SCIP？

[dopejams chan]

Hi，I have met a problem about SCIP recently.

In cp-sat,i provide an initial solution by 'hint'.

How can I add in SCIP？

[Xiang Chen]

Use the solver.SetHint(variables, values) method

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[dopejams chan]

hi, I have used the function SetHint in CP-SAT  .

But it doesn't seem to be available in SCIP.  

[Mizux Seiha]

Are you sure SetHint() is it not available ?

https://github.com/google/or-tools/blob/b37d9c786b69128f3505f15beca09e89bf078a89/ortools/linear_solver/linear_solver.h#L635-L648
and it seems the SCIP backend takes it into account
https://github.com/google/or-tools/blob/b37d9c786b69128f3505f15beca09e89bf078a89/ortools/linear_solver/scip_interface.cc#L743-L773

and it seems binded in python using a custom overload

https://github.com/google/or-tools/blob/b37d9c786b69128f3505f15beca09e89bf078a89/ortools/linear_solver/python/linear_solver.i#L130-L153

[dopejams chan]

Hi, Mizux:

I have used SetHint() to provide a feasible solution,.However ,the  SCIP returns that can't find a solution.And this is a model that I can solve using CP-SAT.

https://groups.google.com/g/or-tools-discuss/c/-PYyjmyrNIk/m/rTttASSFAgAJ
I think I have the same problem as him. How to solve it?

[dopejams chan]

I have checked the SCIP's logs.

It said that 'WARNING: ignore partial solution (0) because unknown rate is too large (0.997967 > 0.85)',but the values i gave is Int.

What is unknown rate?

[Laurent Perron]

Dunno. This is a SCIP warning :-)

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

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[Mizux Seiha]

seems it has been answered here: https://or.stackexchange.com/questions/6240/or-tools-partial-solution-ignored-due-to-unknown-rate-is-too-large

[dopejams chan]

Thanks Mizux. 

However, it still can't give a feasible solution when I used SetHint().

The log is 'all 5 solutions given by solution candidate storage are infeasible

WARNING: LP solver reached time limit, but SCIP time limit is not exceeded yet; you might consider switching the clock type of SCIP

completion of a partial solution failed (time limit exceeded)'.Why?

[dopejams chan]

I found a function in https://github.com/google/or-tools/blob/stable/ortools/linear_solver/scip_interface.cc#L847

how can i use it ?

[dopejams chan]

I have solved the problem.

And the reason why it's wrong is that my decision variable is two dimensional.I didn't turn it into a one-dimensional array and put it in SetHint.

Thank you very much for your valuable suggestions!!!