[Solver Proposal] Pumpkin support #95

• feat: Add pumpkin_solver solver #96

Pumpkin is a solver with a variety of constraints:

The solver currently supports integer variables and a number of (global) constraints:

• Cumulative global constraint.
• Element global constraint.
• Arithmetic constraints: linear integer (in)equalities, integer division, integer multiplication, maximum, absolute value.
• Clausal constraints.

I note that it only says

Pumpkin serves as a backend solver for the MiniZinc modelling language.

I came across Pumpkin when looking for a Rust interface to MiniZinc. I have used good_lp so am now wondering whether it would be possible/desirable to have Pumpkin as a solver in good lp (and if so, how comprehensively out of the many constraint types listed above)

My expectation is that possibly only the linear integer arithmetic inequalities would be supported, but perhaps this would still be desirable?

Edit I plumbed it in and built with the new feature, trying to get some tests to pass…

• main...lmmx:good_lp:feat-pumpkin-solver#diff-ff158e26966b790505d504f34befb9542baea602c5d035314e7b6fc7ffcb1e68