Add support for nonlinear variables

[Aliebc]

Add support for nonlinear variable expressions

Currently, Pulp does not support nonlinear variable expressions, and it will raise an error for such expressions.
`
import pulp as pl

x1 = pl.LpVariable("x1", lowBound=0, upBound=5)
x2 = pl.LpVariable("x2", lowBound=0, upBound=5)

problem = pl.LpProblem("MILP", pl.LpMaximize)

problem += x1 * x1 + x2 * x2

problem += x1 + x2 <= 10

problem.solve()

for v in problem.variables():
print(v.name, v.varValue)

print("Obj: ", pl.value(problem.objective))
`

It gives the following error:
TypeError: Non-constant expressions cannot be multiplied

However, GUROBI supports such expressions.

`
from gurobipy import Model, GRB

model = Model("MILP")

x1 = model.addVar(vtype=GRB.CONTINUOUS, name="x1")
x2 = model.addVar(vtype=GRB.CONTINUOUS, name="x2")

model.addConstr(x1 >= 0)
model.addConstr(x1 <= 5)
model.addConstr(x2 >= 0)
model.addConstr(x2 <= 5)

model.setObjective(x1 * x1 + x2 * x2, GRB.MAXIMIZE)

model.addConstr(x1 + x2 <= 10, "c0")

model.optimize()

for v in model.getVars():
print('%s %g' % (v.varName, v.x))

print('Obj: %g' % model.objVal)
`

Can Pulp support such nonlinear variable expressions with GUROBI?

[pchtsp]

Hello! That's a good point. Unfortunately we try to keep pulp valid for many solvers and sometimes this means not being able to provide the full functionality of each solver. As a workaround, you can build most of the problem in pulp and then manipulate the GUROBI model just before running, as explained here : https://coin-or.github.io/pulp/guides/how_to_configure_solvers.html#using-solver-specific-functionality The example uses cplex but it's valid for the GUROBI solver

…

---------- Forwarded message --------- From: AX ***@***.***> Date: Sun, Jun 23, 2024, 04:37 Subject: [coin-or/pulp] Add support for nonlinear variables (Issue #756) To: coin-or/pulp ***@***.***> Cc: Subscribed ***@***.***> Add support for nonlinear variable expressions Currently, Pulp does not support nonlinear variable expressions, and it will raise an error for such expressions. ` import pulp as pl x1 = pl.LpVariable("x1", lowBound=0, upBound=5) x2 = pl.LpVariable("x2", lowBound=0, upBound=5) problem = pl.LpProblem("MILP", pl.LpMaximize) problem += x1 * x1 + x2 * x2 problem += x1 + x2 <= 10 problem.solve() for v in problem.variables(): print(v.name, v.varValue) print("Obj: ", pl.value(problem.objective)) ` It gives the following error: TypeError: Non-constant expressions cannot be multiplied However, GUROBI supports such expressions. ` from gurobipy import Model, GRB model = Model("MILP") x1 = model.addVar(vtype=GRB.CONTINUOUS, name="x1") x2 = model.addVar(vtype=GRB.CONTINUOUS, name="x2") model.addConstr(x1 >= 0) model.addConstr(x1 <= 5) model.addConstr(x2 >= 0) model.addConstr(x2 <= 5) model.setObjective(x1 * x1 + x2 * x2, GRB.MAXIMIZE) model.addConstr(x1 + x2 <= 10, "c0") model.optimize() for v in model.getVars(): print('%s %g' % (v.varName, v.x)) print('Obj: %g' % model.objVal) ` Can Pulp support such nonlinear variable expressions with GUROBI? — Reply to this email directly, view it on GitHub <#756>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABJUZ4YETRSU2I3NQEKGTQ3ZIYYFRAVCNFSM6AAAAABJX6CYESVHI2DSMVQWIX3LMV43ASLTON2WKOZSGM3DQMJWGUYDCMQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Aliebc]

OK. Thank you very much!