Question

我有以下型号：

from gurobipy import *

n_units = 1
n_periods = 3
n_ageclasses = 4

units = range(1,n_units+1)
periods = range(1,n_periods+1)
periods_plus1 = periods[:]
periods_plus1.append(max(periods_plus1)+1)
ageclasses = range(1,n_ageclasses+1)
nothickets = ageclasses[1:]


model = Model('MPPM')

HARVEST = model.addVars(units, periods, nothickets, vtype=GRB.INTEGER, name="HARVEST")
FOREST = model.addVars(units, periods_plus1, ageclasses, vtype=GRB.INTEGER, name="FOREST")


model.addConstrs((quicksum(HARVEST[(k+1), (t+1), nothicket] for k in range(n_units) for t in range(n_periods) for nothicket in nothickets)  == FOREST[unit, period+1, 1] for unit in units for period in periods if period < max(periods_plus1)), name="A_Thicket")

我在制定约束时遇到问题。我想要为每个单位和每个时期总结变量HARVEST的nothickets部分。具体地说我想要x _{k = 1，t = 1,2} + x _{k = 1，t = 1,3} + x _{k = 1，t = 1 ，4
等等。这应该导致约束矩阵的每行只有三个。但是根据上面的表述我得到了9个。
我尝试在总和之外使用for循环，但这会导致另一个问题：}

 for k in range(n_units):
    for t in range(n_periods):
        model.addConstrs((quicksum(HARVEST[(k+1), (t+1), nothicket] for nothicket in nothickets)  == FOREST[unit,period+1, 1] for unit in units for period in periods if period < max(periods_plus1)), name="A_Thicket")

通过这个公式，我得到了这个矩阵： constraint matrix

但我想要的是：

row_idx | col_idx | coeff
0   | 0  | 1
0   | 1  | 1
0   | 2  | 1
0   | 13  | -1
1   | 3  | 1
1   | 4  | 1
1   | 5  | 1
1   | 17  | -1
2   | 6  | 1
2   | 7  | 1
2   | 8  | 1
2   | 21  | -1

有人可以帮我重新制定这种约束吗？

Answer 1

这对我有用：

 model.addConstrs((HARVEST.sum(unit, period, '*') == ...

Gurobi：我怎样才能将变量的一部分加起来？

1 个答案: