CODEWITHSUNDEEP
cplexpyomo
dylee
dylee

Reputation: 75

Pyomo - CPLEX returns no solutions, no constraints, no variables

I'm just starting out with Pyomo. I tried to solve example problems from Pyomo Overview using CPLEX 12.8, Python 3.6 on Ubuntu 14.06.

# abstract1.py
from __future__ import division
from pyomo.environ import *

model = AbstractModel()

model.m = Param(within=NonNegativeIntegers)
model.n = Param(within=NonNegativeIntegers)

model.I = RangeSet(1, model.m)
model.J = RangeSet(1, model.n)

model.a = Param(model.I, model.J)
model.b = Param(model.I)
model.c = Param(model.J)

# the next line declares a variable indexed by the set J
model.x = Var(model.J, domain=NonNegativeReals)

def obj_expression(model):
    return summation(model.c, model.x)

model.OBJ = Objective(rule=obj_expression)

def ax_constraint_rule(model, i):
    # return the expression for the constraint for i
    return sum(model.a[i,j] * model.x[j] for j in model.J) >= model.b[i]

# the next line creates one constraint for each member of the set model.I
model.AxbConstraint = Constraint(model.I, rule=ax_constraint_rule)

# abstract1.dat
param m := 1 ;
param n := 2 ;

param a :=
1 1 3
1 2 4
;

param c:=
1 2
2 3
;

param b := 1 1 ;

Running this $ pyomo solve abstract1.py abstract1.dat --solver=cplex , however, returns no solution. In fact, the model seems to have no constraints and no variables, and produces the following results.

# ==========================================================
# = Solver Results                                         =
# ==========================================================
# ----------------------------------------------------------
#   Problem Information
# ----------------------------------------------------------
Problem: 
- Lower bound: -inf
  Upper bound: inf
  Number of objectives: 1
  Number of constraints: 0
  Number of variables: None
  Number of nonzeros: None
  Sense: unknown
# ----------------------------------------------------------
#   Solver Information
# ----------------------------------------------------------
Solver: 
- Status: ok
  Termination condition: unknown
  Error rc: 0
  Time: 0.01150965690612793

I have tried the ConcreteModel example, as well as abstract2.py, but still get the above results. Anyone have any idea what's happening, or where I can look into?

Upvotes: 1

Views: 980

Answers (1)

dylee
dylee

Reputation: 75

I was pointed to this solution. It was a silly mistake, I had a space in the name of my working directory (e.g., 'two Words'). Getting rid of the space as should be standard practice for a developer (I'm not a developer by training) (e.g., 'twoWords') fixed this issue.

Upvotes: 1

Related Questions