如何在CPLEX python中编写条件约束? [英] how to write a conditional constraint in CPLEX python?

问题描述

我有一个具有一个二进制变量x [i] [j] [k]的模型.我需要添加一个满足此条件的约束:

I have a model that has one binary variable x [i] [j] [k]. I need to add a constraint that fullfils this condition:

if x[i][j][k1]==1  and  x[j][i][k2]==1 

Then:

 k2-k1>8

我有此代码，但我认为这是不正确的:

I have this code but I assum it is not correct :

  mdl.add((y[(i,j,k)]+y[(j,i,k1)]==2),(k1-k>8) )

我也这样:

 mdl.add(mdl.if_then(y[(i,j,k1)]+y[(j,i,k2)]==2, k2-k1>8))

但是我得到了这个错误:

but I got this error:

    raise DOcplexException(resolved_message)

DOcplexException: Expecting linear constraint, got: False

如何使用cplex python API对此建模?

How can I model this with cplex python API?

推荐答案

让我分享

https://www.linkedin.com/脉冲/制作优化-简单-python-alex-fleischer/

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.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

for v in mdl.iter_integer_vars():
   print(v," = ",v.solution_value)

print()
print("with if nb buses 40 more than 3  then nbBuses30 more than 7")

#if then constraint
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) 

以及如果要查看和在

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.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

for v in mdl.iter_integer_vars():
   print(v," = ",v.solution_value)

print()
print("with if nb buses 40 more than 3 and less than 7 then nbBuses30 more than 7")

#if then constraint
mdl.add(mdl.if_then((nbbus40>=3) + (nbbus40<=7)>=2,nbbus30>=7))
mdl.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()



for v in mdl.iter_integer_vars():
    print(v," = ",v.solution_value) 

您也可以重写

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.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()

for v in mdl.iter_integer_vars():
   print(v," = ",v.solution_value)

print()
print("with if nb buses 40 more than 3 and less than 7 then nbBuses30 more than 7")

#if then constraint
mdl.add((((nbbus40>=3) + (nbbus40<=7)>=2))<=(nbbus30>=7))
mdl.minimize(nbbus40*500 + nbbus30*400)

mdl.solve()



for v in mdl.iter_integer_vars():
    print(v," = ",v.solution_value) 

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