64-bit indices

[mlubin]

PaPILO is very impressive work, and I'm evaluating using it in a particular application. One issue I noticed is that PaPILO currently uses int to index variables, constraints, and to count the number of nonzeros in the constraint matrix. int is typically 4 bytes. A number of solvers support more than 2^31 ≈ 2 billion variables, constraints, or nonzero entries. Is this restriction intentional, and how difficult would it be to relax?

[lgottwald]

It would not be super difficult, would be mostly just looking to replace int by int64_t where it is used for columns/rows/. Might trigger a few bugs if done uncarefully but if lucky it might already work to just replace all int as int64 in PaPILO source files.