[英]transfer CPLEX mathematical model from C++ to Python
I have programmed my mathematical model in C++ using CPLEX,now I want to transfer it to Python using docplex.mp.model I met some problems in adding constraints. I have programmed my mathematical model in C++ using CPLEX,now I want to transfer it to Python using docplex.mp.model I met some problems in adding constraints. In C++,I am used to add constraints like this
在C++中,我习惯这样添加约束
for (j = NumD; j < NumDC; j++)
{
IloExpr v(env);
for (i = 0; i < NumDC; i++)
{
for (k = 0; k < NumV; k++)
{
v += xijk[i][j][k];
}
}
model.add(v >= 1);
}
I write this code in python like this:我在 python 中这样写代码:
for j in range(NumD,NumDC):
v = model.linear_expr()
for i in range(NumDC):
for k in range(NumV):
v+=xijk[i,j,k]
model.add_constraint(v >= 1)
Is this right?这是正确的吗? Thanks:)
谢谢:)
You could use python sum or even model.sum您可以使用 python sum 甚至 model.sum
NB: Always use model.sum instead of python sum that is O(n*n)注意:始终使用 model.sum 而不是 python 总和,即 O(n*n)
See example in参见示例
https://github.com/AlexFleischerParis/zoodocplex/blob/master/zoodatainalistoftuple.py https://github.com/AlexFleischerParis/zoodocplex/blob/master/zoodatainalistoftuple.py
from docplex.mp.model import Model
# Data
Buses=[
(40,500),
(30,400)
]
nbKids=300
# Indexes
busSize=0;
busCost=1;
for b in Buses:
print("buses with ",b[busSize]," seats cost ",b[busCost])
mdl = Model(name='buses')
#decision variables
mdl.nbBus=mdl.integer_var_dict(Buses,name="nbBus")
# Constraint
mdl.add_constraint(mdl.sum(mdl.nbBus[b]*b[busSize] for b in Buses) >= nbKids, 'kids')
# Objective
mdl.minimize(mdl.sum(mdl.nbBus[b]*b[busCost] for b in Buses))
mdl.solve()
# Display solution
for b in Buses:
print(mdl.nbBus[b].solution_value," buses with ",b[busSize]," seats");
"""
which gives
buses with 40 seats cost 500
buses with 30 seats cost 400
6.0 buses with 40 seats
2.0 buses with 30 seats
"""
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