solver.Add(solver.Sum()) is crazy slow

[Nathan Petty]

Potential game breaker here:

using python, adding constraints of any real world size is prohibitively slow using solver.Add(solver.Sum(blah))

adding a mere 2k constraints takes 60s on top tier i7.  That's slower than the solve itself!  Each constraint has about 10k vars (the problem itself has 90k vars)

RIP or-tools?  bug fix in the works?  maybe a workaround for now?

Thanks, Nathan

[Nathan Petty]

Still struggling with this.  Is anyone else noticing very slow runtime on adding constraints of any substantial size?  The big problem with this and the reason it could temporarily be a game breaker for or-tools, is that loading the problem is taking longer than solving the problem.   Any ideas would be greatly appreciated.  Thanks

[Laurent Perron]

I have no good answer that do not use python for it.

I profiled it, just storing the data in the hash map, and rereading it to pass to the C++ makes for most of the time.

At best, I can gain a 2x, but I am not sure we can do better with python. I would love to be proven wrong.

Thanks

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

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[Nathan Petty]

Thanks Laurent for looking into it. Does this mean I should go to c++ ?

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[Laurent Perron]

Can you write the same loop in C++ and see if it is worth it?