Choosing a solver¶

How to solve on a solver other than HiGHS, pass it options, or write the model to a file. HiGHS ships with specsolve and is the default.

See which solvers this build has¶

Name a solver that does not exist, and the refusal lists the ones that do:

import specsolve as sps

try:
    sps.solve('examples/dispatch.yaml', {}, solver_name='cplex')
except sps.errors.SpecsolveError as exc:
    print(exc)

unknown solver 'cplex' — this build solves with gurobi, highs, xpress.

Install the solver¶

Every solver except HiGHS comes with the extra of the same name:

pip install "specsolve[gurobi]"

Name it in the call¶

solver_name= goes on solve, Model.solve and solve_over:

result = sps.solve('dispatch.yaml', sources, solver_name='gurobi')

Pass solver options¶

solver_options= goes to the solver verbatim, in its own vocabulary:

result = sps.solve('dispatch.yaml', sources, solver_name='gurobi', solver_options={'TimeLimit': 60})

A solver that cannot take the model¶

solve refuses a model the solver cannot take, such as SOS sets on HiGHS, and names the solvers that do. To ask without solving, build and check:

import specsolve as sps

model = sps.build('dispatch.yaml', sources)
model.check('gurobi')

The full table is what each sink takes.

Write the model to a file¶

For a solver specsolve does not run, write the model. The suffix picks the format, .lp or .mps:

sps.write('dispatch.yaml', sources, 'dispatch.lp')