Collect all feasible solutions

[ivborissov]

Hi,

is it possible to add support for optimizer_attribute to collect all feasible solutions:
set_optimizer_attribute(model, "constraints/countsols/collect", 1)

The question appeared on discourse and it seems SCIP is the only free MIP solver, which supports it
https://discourse.julialang.org/t/right-solver-for-jump-to-find-every-solution-of-a-linear-system-of-equations-with-integer-solutions/44709
https://www.scipopt.org/doc/html/COUNTER.php

[matbesancon]

Hi, yes this is abolutely possible.
I would be available to help if you open a PR but don't have time myself now.

The steps would be:

1. creating the MOI optimizer attribute
2. implement get and set for it
3. pass the parameter to SCIP when set (that way we do not need to store it)

[ivborissov]

Thanks for such a quick response!

Will try to implement it.

[matbesancon]

hi @ivborissov, in the meantime, was the solution of setting the raw parameter "constraints/countsols/collect" working for you?

[ivborissov]

Hi @matbesancon Sorry, I didn't have time to get back to this issue yet( But as I remember simply setting set_optimizer_attribute(model, "constraints/countsols/collect", 1) didn't work for me.