PuLP：目标函数：连接多个lpSum

Question

我试图将几个lpSum表达式连接为一个长表达式，这将是我的目标函数。 但是，我尝试以优雅的方式合并这些表达式会导致不良结果。

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

我已经尝试了不同的嵌套方法，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)]

输出会执行应有的操作。 但是，这既不是很好的代码，也不能分配给目标函数。 有没有明智的实施方式？

谢谢！

Answer 1

没有看到错误，我可以百分百确定，但是我认为您在lpsum中包含的名称引起了问题，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