我需要在 python 中编写一个模型来用 gurobi 解决它。该模型包含一个平方根:Σ(h z a*√(SI+TR))(这是目标函数)
因为 Gurobi 不支持平方根,所以我将目标函数转换为:Σ(h z a*Z)(目标函数)
SI+TR<=Z*Z(额外约束)
Z>=0(额外约束)
但是现在Gurobi还是报错:GurobiError: Q matrix is not positive semi-definite (PSD)
我如何让 Gurobi 解决这个模型?代码:(从第 143 行开始到第 199 行)
#create objective
for j in intermediateStage:
for d in demandStage:
m.setObjective(quicksum(h[d]*Z*VarDemand[d]*Z2[d] for d in demandStage)+quicksum(h[j]*Z*Z1[j]*Var[j] for j in intermediateStage),GRB.MINIMIZE)
#addconstraints
for j in intermediateStage:
m.addConstr(R[j]-SI[j]<=T[j])
for d in demandStage:
m.addConstr(R[d]-SI[d]<=T[d])
for k in supplyStage:
m.addConstr(R[k]-SI[k]<=T[k])
for j in intermediateStage:
m.addQConstr(SI[j]+T[j]-R[j]<=Z1[j]*Z1[j])
for d in demandStage:
m.addQConstr(SI[d]+T[d]-R[d]<=Z2[d]*Z2[d])
for k in supplyStage:
for j in intermediateStage:
m.addConstr(R[k]-SI[j]<=0)
for j in intermediateStage:
for d in demandStage:
m.addConstr(R[j]-SI[d]<=0)
for d in demandStage:
m.addConstr(R[d]<=E[d])
for k in supplyStage:
m.addConstr(SI[k]==0)
for k in supplyStage:
m.addConstr(SI[k]>=0)
for k in supplyStage:
m.addConstr(R[k]>=0)
for d in demandStage:
m.addConstr(SI[d]>=0)
for d in demandStage:
m.addConstr(R[d]>=0)
for d in demandStage:
m.addConstr(Z2[d]>=0)
for j in intermediateStage:
m.addConstr(SI[j]>=0)
for j in intermediateStage:
m.addConstr(R[j]>=0)
for j in intermediateStage:
m.addConstr(Z1[j]>=0)
m.optimize()
print SI[j]
print R[j]
回溯(最后一次调用):文件“C:\gurobi600\win32\examples\python\safetyStock.py”,第 230 行,在安全库存(需求,中级,alfa)文件“C:\gurobi600\win32\examples\python \safetyStock.py”,第 192 行,在 safestock m.optimize() 文件“model.pxi”,第 536 行,在 gurobipy.Model.optimize (../../src/python/gurobipy.c:37543) GurobiError : Q 矩阵不是半正定的 (PSD)