Chuffed free search

[Roberto Amadini]

Hi,

I noticed that with the attached model/data, the performance difference of Chuffed is noticeable with vs. without the -f parameter (on my laptop, with free search it takes around 90 seconds, while without -f it takes around 20 seconds)

This looks weird to me, as no search heuristics is specified so I was assuming that in this case Chuffed would resort to free search, so using -f would be useless (in fact, e.g., for Gecode there is no difference when using -f)

Do you know what happens to Chuffed when -f is not set and no search heuristics is specified?

Thanks,

Roberto

[Jip Dekker]

Hi Roberto,

When the "-f" flag is not set for Chuffed, then the VSIDS search method is not enabled: https://github.com/chuffed/chuffed/blob/91c60ec6c1613b8e7f5595dce4dca370dbbc5864/chuffed/core/options.cpp#L591-L592

The FlatZinc interface in turn will always make sure that (default) branching instructions are put in place for the solver: https://github.com/chuffed/chuffed/blob/91c60ec6c1613b8e7f5595dce4dca370dbbc5864/chuffed/flatzinc/flatzinc.cpp#L565-L602

You are of course right that the free-search strategy could always be used when no branching instructions are provided in a FlatZinc model, but this is at least not what the current implementation does.

Cheers,

Jip