Formulate optimization problems using sympy expressions and solve them using interfaces to third-party optimization software (e.g. GLPK).
Project description
optlang
Vision
optlang is a Python package for solving mathematical optimization problems, i.e. maximizing or minimizing an objective function over a set of variables subject to a number of constraints. Optlang provides a common interface to a series of optimization tools, so different solver backends can be changed in a transparent way.
Optlang takes advantage of the symbolic math library sympy to allow objective functions and constraints to be easily formulated from symbolic expressions of variables (see examples).
Installation
Install using pip
pip install optlang
Local installations like
python setup.py install
might fail installing the dependencies (unresolved issue with easy_install). Running
pip install -r requirements.txt
beforehand should fix this issue.
Documentation
The documentation for optlang is provided at readthedocs.org.
Dependencies
And at least one of the following
Example
Formulating and solving the problem is straightforward (example taken from GLPK documentation):
from optlang.glpk_interface import Model, Variable, Constraint, Objective x1 = Variable('x1', lb=0) x2 = Variable('x2', lb=0) x3 = Variable('x3', lb=0) c1 = Constraint(x1 + x2 + x3, ub=100) c2 = Constraint(10 * x1 + 4 * x2 + 5 * x3, ub=600) c3 = Constraint(2 * x1 + 2 * x2 + 6 * x3, ub=300) obj = Objective(10 * x1 + 6 * x2 + 4 * x3, direction='max') model = Model(name='Simple model') model.objective = obj model.add([c1, c2, c3]) status = model.optimize() print "status:", model.status print "objective value:", model.objective.value for var_name, var in model.variables.iteritems(): print var_name, "=", var.primal
The example will produce the following output:
status: optimal objective value: 733.333333333 x2 = 66.6666666667 x3 = 0.0 x1 = 33.3333333333
Future outlook
Mosek interface (provides academic licenses)
GAMS output (support non-linear problem formulation)
DEAP (support for heuristic optimization)
Interface to NEOS optimization server (for testing purposes and solver evaluation)
Automatically handle fractional and absolute value problems when dealing with LP/MILP/QP solvers (like GLPK, CPLEX etc.)
The optlang trello board also provides a good overview of the project’s roadmap.
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