加载模型时出现意外异常：(0, 0)

Question

我刚开始使用 pyomo 框架和 python。我正在尝试解决简单的模型。当我制定 objective 函数时，在运行代码

之前收到以下错误

按键错误：(0, 0)

问题的表述如下： Formulation

代码：

from pyomo.environ import *  

N = 3
M = 4
P = 3
d = {(1, 1): 1.7, (1, 2): 7.2, (1, 3): 9.0, (1, 4): 8.3,
(2, 1): 2.9, (2, 2): 6.3, (2, 3): 9.8, (2, 4): 0.7,
(3, 1): 4.5, (3, 2): 4.8, (3, 3): 4.2, (3, 4): 9.3}

seq = ConcreteModel()
seq.Locations = range(N) #Set N
seq.Customers = range(M) #Set M

seq.x = Var(seq.Locations, seq.Customers, bounds=(0.0, 1.0)) #x[n,m]
seq.y = Var(seq.Locations, within=Binary)

seq.obj=Objective(expr = sum( d[n,m]*seq.x[n,m] for n in seq.Locations for m in seq.Customers))

seq.single_x = ConstraintList()
for m in seq.Customers:
    seq.single_x.add(
        sum(seq.x[n,m] for n in model.Locations ) == 1.0)
    
seq.bound_y = ConstraintList()
for n in seq.Locations:
    for m in seq.Customers:
        seq.bound_y.add( seq.x[n,m] <= seq.y[n] )

seq.num_facilities = Constraint(
    expr=sum( seq.y[n] for n in seq.Locations) == P)

可能是什么问题？谢谢！

Answer 1

您遇到的关键错误是因为您的字典 d 没有 [0, 0] 的条目。

我的建议是将所有内容都带入模型（请参阅下面我的编辑）。这样你就可以“漂亮地打印”模型，这使得在构建时排除故障变得非常容易。

祝你好运！

from pyomo.environ import *  

N = 3
M = 4
P = 3
d = {(1, 1): 1.7, (1, 2): 7.2, (1, 3): 9.0, (1, 4): 8.3,
(2, 1): 2.9, (2, 2): 6.3, (2, 3): 9.8, (2, 4): 0.7,
(3, 1): 4.5, (3, 2): 4.8, (3, 3): 4.2, (3, 4): 9.3}

seq = ConcreteModel()

###  SETS
seq.Locations = Set(initialize = list(range(1, N+1))) #Set N  # note the capitalization Set, the pyomo type
seq.Customers = Set(initialize = list(range(1, M+1))) #Set M

### PARAMS
seq.d = Param(seq.Locations, seq.Customers, initialize=d)

### VARS
seq.x = Var(seq.Locations, seq.Customers, bounds=(0.0, 1.0)) #x[n,m]
seq.y = Var(seq.Locations, within=Binary)

seq.obj=Objective(expr = sum( seq.d[n,m]*seq.x[n,m] for n in seq.Locations for m in seq.Customers))

seq.single_x = ConstraintList()
for m in seq.Customers:
    seq.single_x.add(
        sum(seq.x[n,m] for n in seq.Locations ) == 1.0)
    
seq.bound_y = ConstraintList()
for n in seq.Locations:
    for m in seq.Customers:
        seq.bound_y.add( seq.x[n,m] <= seq.y[n] )

seq.num_facilities = Constraint(
    expr=sum( seq.y[n] for n in seq.Locations) == P)

seq.pprint()

加载模型时出现意外异常：(0, 0)

Unexpected exception while loading model: (0, 0)

pyomo