Support MOI.VariableBasisStatus and MOI.ConstraintBasisStatus attributes

[mzy2240]

Currently when running lp_sensitivity_report after getting an optimal solution, the following error would be raised

Unable to query LP sensitivity information because this solver does not support querying the status of variables in the optimal basis.

[odow]

AmplNLWriter does not support returning basis information for the variables and constraints.

Can you point to any examples or options where calling an AMPL executable would write out the basis information to the .sol file?

[odow]

Some solvers return a sstatus suffix. Here's a Gurobi solve:

shell> cat model.nl
g3 1 1 0
 1 1 1 0 0 0
 0 1
 0 0
 0 0 0
 0 0 0 1
 0 0 0 0 0
 1 1
 0 0
 0 0 0 0 0
C0
n0
O0 1
n0
x1
0 0
r
1 1
b
2 0
k0
J0 1
0 1
G0 1
0 1

shell> cat model.sol
Gurobi 9.5.1: optimal solution; objective 1

Options
3
1
1
0
1
1
1
1
1
1
objno 0 0
suffix 0 1 8 0 0
sstatus
0 1
suffix 1 1 8 0 0
sstatus
0 2

but adding basis support to AmplNLWriter seems very niche. Just use the proper solver APIs instead. The NL files are really intended for nonlinear programs.

[odow]

Closing as won't fix. I don't see a need for this. The solvers which support basis status have corresponding packages with proper APIs.