PuLP:目标函数:连接多个lpSum

Question

我正在尝试将几个lpSum表达式连接成一个长表达式，这将是我的目标函数。然而，我试图以一种优雅的方式合并这些表达式，导致了不想要的结果。

我想要这样的东西：

a = pulp.lpSum(...)
b = pulp.lpSum(...)
c = pulp.lpSum(...)

prob += a + b - c

我的代码更加具体：

    alloc_prob = pulp.LpProblem("Supplier Allocation Problem", pulp.LpMinimize)

    TPC_func = pulp.lpSum(X[s][p]*procCosts[s][p] for s in supplier for p in 
    project), "Total Procurement Costs"
    TTC_func = pulp.lpSum(X[s][p]*transCosts[s][p] for s in supplier for p in 
    project), "Total Transportation Costs (incl. taxes/duties)"
    TD_func = pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus / ton [€/t]'][c] for 
    c in company), "Total Discounts"`

    # Objective function: TPC + TTC - TD -> min
    alloc_prob += TPC_func  + TTC_func - TD_func

我已经尝试过不同的嵌套方法，例如：

    prob += [pulp.lpSum(X[s][p]*procCosts[s][p] + X[s][p]*transCosts[s][p] for s 
    in supplier for p in project) - pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus 
    / ton [€/t]'][c] for c in company)]

输出做了它应该做的事情。然而，这既不是一个很好的代码，也不能分配给目标函数。有没有一种聪明的实现方式？

谢谢!

Answer 1

在看不到错误的情况下，我可以100%确定，但我认为您在lpsum中包含的名称导致了问题，请尝试以下操作

alloc_prob = pulp.LpProblem("Supplier Allocation Problem", pulp.LpMinimize)

TPC_func = pulp.lpSum(X[s][p]*procCosts[s][p] for s in supplier for p in 
project)
TTC_func = pulp.lpSum(X[s][p]*transCosts[s][p] for s in supplier for p in 
project)
TD_func = pulp.lpSum(X_SEP[c][1]*discountFactor['Bonus / ton [€/t]'][c] for 
c in company)

# Objective function: TPC + TTC - TD -> min
alloc_prob += TPC_func  + TTC_func - TD_func