feat: Add pumpkin_solver solver

[lmmx]

• Following [Solver Proposal] Pumpkin support #95

• feat(pumpkin-solver): add Pumpkin solver integration to Cargo features and solvers
• fix(temporary): unsure how to set objective bounds properly, hotfix [-1000, +1000]

I’m not sure about a couple of things here:

• Could I get feedback on whether I’ve added the conditional compilation directives correctly in lib.rs?
• I have temporarily set bounds of [-1000, +1000] but obviously this needs to be done properly

TODO

• Remove solve once assertion (ownership model precludes reuse) 0adc5c6
• Add to CI 3dd3330
• Add to README
  • Solvers table row b254116
  • Solvers section 127c244
• Fix CI test failures
  • default solver not exported (here) - fixed in a550c97
    • TODO: cargo test --no-default-features --features pumpkin-solver should pass
• Add more tests
• Work out how to set bounds properly in objective var (remove [-1000, +1000] hotfix)

[lovasoa]

The overall approach looks good to me. You may want to add some more tests, and update the README.

[lovasoa]

You also need to update the CI to test the new solver: https://github.com/rust-or/good_lp/blob/main/.github/workflows/rust.yml

[lovasoa]

https://github.com/rust-or/good_lp/blob/main/CONTRIBUTING.md

[lmmx]

Thanks a lot, I added pumpkin-solver* to the table with a no on the WASM box but I am not actually sure if that is something that needs special support or if you get it out of the box via good_lp

• edit I tried and there was a specific requirement for Unix handlers so I can confirm WASM is not available (I imagine a workaround could be to stub out a workspace crate for the signal hooks crate providing SIGINT but it's better to fix upstream) WebAssembly compatible? ConSol-Lab/Pumpkin#161

*I feel like pumpkin would be a nicer feature name but I don’t know if it’s preferable to keep it exactly the same as the crate name…

I’ll try using it with existing good_lp code and see if I can road test it this week, add those missing tests and try to find a solution to the objective var bounds