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[英]How to use cplex or gurobi solver with cvxopt in Python?
[英]How to use MIPGap and TimeLimit from Gurobi in python?
我正在研究大規模的 MILP。 所以我必須將時間限制設置為一個合理的值,或者我必須將 MIPGap 設置為一個合理的水平。 我已經知道 gurobi 的文檔。
MIPGap: https ://www.gurobi.com/documentation/6.5/refman/mipgap.html
時間限制: https ://www.gurobi.com/documentation/8.0/refman/timelimit.html#parameter:TimeLimit
MIPGap Gurobi 在找到最優解的百分比時將停止
TimeLimit Gurobi 將在一定時間后停止。
但是你能給我一個例子,例如將時間限制設置為 5 分鍾或將 MIPGap 設置為 5% 嗎?
我不知道如何准確實現這些字符?
請幫助我我對python很陌生
我試過了,但這不起作用
model.Params.TimeLimit = 5
model.setParam("MIPGap", mipgap)
這是我的模型的簡短版本
from gurobipy import *
import csv
import geopandas as gpd
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
from pandas.core.common import flatten
import math
################################# SOLVE function START ###################################################################
def solve(
vpmaint, wpunit, wuunit, vumaint,
kfuel, koil, kbio,
hb, ht,
cj, ci,
zinvestp, zinvestu,
DEMAND, DEMANDM,
LOCATION, SOURCE, BTYPE, SOURCEM,
osi, oij, ojm
):
model = Model("Biomass to liquid supply chain network design")
################################# SOLVE function END ###################################################################
####################################################### variable section START ####################################################################################################
#binary variables ############################# Binary 1-2 ####################################################
#binary 1: Pyrolyse i with capacity p open?
fpopen = {}
for i in LOCATION:
for p in R:
fpopen[i,p] = model.addVar(vtype = GRB.BINARY,name = "fpopen_%s_%s" % (i,p))
#binary 2: Upgrading j with capacity r and technology t open?
fuopen = {}
for j in LOCATION:
for r in R:
for t in TECHNOLOGY:
fuopen[j,r,t] = model.addVar(vtype = GRB.BINARY,name = "fuopen_%s_%s_%s" % (j,r,t))
################################################ continous variables Integer 1-9 #############################################################
#integer 1: Mass of Biomass type b from Source s to Pyrolyse i
xsi = {}
for s in SOURCE:
for i in LOCATION:
for b in BTYPE:
xsi[s,i,b] = model.addVar(vtype = GRB.INTEGER,name = "xsi_%s_%s_%s" % (s,i,b))
#integer 2:Mass of Biomass type b from Source s to Pyrolyse i
xjm = {}
for j in LOCATION:
for m in DEMAND:
xjm[j,m] = model.addVar(vtype = GRB.INTEGER,name = "xjm_%s_%s" % (j,m))
model.update()
model.modelSense = GRB.MAXIMIZE
####################################################### Objective Function START
model.setObjective(
#quicksum(DEMANDM[m] * l for m in DEMANDM )
quicksum(xjm[j,m] * l for j in LOCATION for m in DEMAND)
- quicksum(ainvest[i] + aoperation[i] + aprod[i] for i in LOCATION)
- quicksum(einvest[j] + eoperation[j] + eprod[j] for j in LOCATION)
## ......
####################################################### Constraints
############################## Satisfy Demand Constraint 1-3
# Constraint 1: Always Satisfy Demand at marketplace m
for m in DEMAND:
model.addConstr(quicksum(xjm[j,m] for j in LOCATION) <= int(DEMANDM[m]))
# for m in DEMAND:
# model.addConstr(quicksum(x[j,m] for j in LOCATION) >= DEMANDM[m])
# Constraint 2: The amount of bio-oil sent from pyrolyse station i to Upgrading
###...Here are more constraints
model.optimize()
model.getVars()
model.MIPGap = 5
model.Params.TimeLimit = 1.0
model.setParam("MIPGap", mipgap)
您需要在調用 Model.optimize() 之前設置參數。 此外,MIPGap 和 TimeLimit 的單位分別是分數和秒。 所以你的代碼應該是:
model.Params.MIPGap = 0.05 # 5%
model.Params.TimeLimit = 300 # 5 minutes
model.optimize()
或者,您可以調用模型的setParam()
方法:
model.setParam('MIPGap', 0.05)
model.setParam('Timelimit', 300)
我已經有幾年沒有運行過這段代碼了……我沒有 Gurobi 許可證了。 但是,這樣的事情應該有效。 你沒有提到你如何編碼你的模型。 以下來自pyomo
腳本。 我認為類似的東西會起作用,但是您可以處理求解器實例。
solver = SolverFactory("gurobi")
solver.options['timeLimit'] = 1200 # seconds
solver.options['mipgap'] = 0.01
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