ctzhu / docplex

A mirror of IBM's DOCPLEX, a Python modelling package for operational research

DOcplex, IBM® Decision Optimization Modeling for Python

Welcome to the IBM® Decision Optimization CPLEX Modeling for Python. Licensed under the Apache License v2.0.

With this library, you can quickly and easily add the power of optimization to your application. You can model your problems by using the Python API and solve them on the cloud with the IBM® Decision Optimization on Cloud service or on your computer with IBM® ILOG CPLEX Optimization Studio.

This library is composed of 2 modules:

• IBM® Decision Optimization CPLEX Optimizer Modeling for Python - with namespace docplex.mp
• IBM® Decision Optimization CP Optimizer Modeling for Python - with namespace docplex.cp

Solving with CPLEX locally requires that IBM® ILOG CPLEX Optimization Studio V12.7.1 or V12.8 is installed on your machine.

Solving with the IBM® Decision Optimization on Cloud service requires that you register for an account and get the API key.

This library is numpy friendly.

Documentation

Examples

Installation

• pip install docplex

docplex's Issues

How to use Continuous Variables for IF-THEN constraints on DOCPLEX (Python)?

I'm using DOCPLEX to build up a Mixed Integer Linear Programming (MILP) problem which is then solved via CPLEX on Python. However, upon trying to solve the MILP problem using IF-THEN constraints, I receive the following error:

DOcplexException: Model.if_then(), nbBus40 >= 3.0 is not discrete

This is happening because I have declared nbbus40 variable to be continuous, as shown in the code below:

from docplex.mp.model import Model
mdl = Model(name='buses')
nbbus40 = mdl.continuous_var(name='nbBus40')
nbbus30 = mdl.integer_var(name='nbBus30')
mdl.add_constraint(nbbus40*40 + nbbus30*30 >= 300, 'kids')
mdl.add(mdl.if_then((nbbus40>=3),(nbbus30>=7)))
mdl.minimize(nbbus40*500 + nbbus30*400)
mdl.solve()
for v in mdl.iter_integer_vars():
print(v," = ",v.solution_value)

However, if I keep the nbbus40 variable as an integer, then I get the solution to the MILP problem, as shown below:

from docplex.mp.model import Model
mdl = Model(name='buses')
nbbus40 = mdl.integer_var(name='nbBus40')
nbbus30 = mdl.integer_var(name='nbBus30')
mdl.add_constraint(nbbus40*40 + nbbus30*30 >= 300, 'kids')
mdl.add(mdl.if_then((nbbus40>=3),(nbbus30>=7)))
mdl.minimize(nbbus40*500 + nbbus30*400)
mdl.solve()
for v in mdl.iter_integer_vars():
print(v," = ",v.solution_value)

RESULT:

nbBus40 = 0
nbBus30 = 10.0

How can I use the IF-THEN constraint in DOCPLEX for continuous variables?

invalid escape sequences

Your code presents some invalid escape sequences that are considered errors from python 11. Please check: https://docs.astral.sh/ruff/rules/invalid-escape-sequence/
A clear and concise description of the bug.

Steps To Reproduce
With CI workflow for analyzing the code, errors like:

E SyntaxError: invalid escape sequence '?'

rises in the comment lines

Expected Behavior
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Environment

• for all the OS
• for python in range 3.9 to 3.12