如何用Python在Cplex中表示线性规划问题
我试图使用IBM的Cplex解决一个线性编程问题,同时从Python调用它 问题是最小化a+c 受Ax'=m'的约束 其中x=[a,b,c] A=[[20,0,0],[0,20,30]] m=[20,30] a,b,c在0和1之间 该问题的一个正确解决方案是a=1、b=0和c=1。但是Cplex给出了解决方案,a=1,b=1,c=0。这个问题的表述有错误,但我不知道在哪里。代码如下如何用Python在Cplex中表示线性规划问题,python,linear-programming,cplex,Python,Linear Programming,Cplex,我试图使用IBM的Cplex解决一个线性编程问题,同时从Python调用它 问题是最小化a+c 受Ax'=m'的约束 其中x=[a,b,c] A=[[20,0,0],[0,20,30]] m=[20,30] a,b,c在0和1之间 该问题的一个正确解决方案是a=1、b=0和c=1。但是Cplex给出了解决方案,a=1,b=1,c=0。这个问题的表述有错误,但我不知道在哪里。代码如下 import cplex from cplex.exceptions import CplexError impo
import cplex
from cplex.exceptions import CplexError
import sys
my_obj = [1.0, 0.0, 1.0]
my_ub = [1.0] * len(my_obj)
my_lb = [0.0] * len(my_obj)
my_colnames = ["a", "b", "c"]
my_rhs = [20.0, 30.0]
my_rownames = ["c1", "c2"]
my_sense = "E" * len(my_rownames)
def populatebynonzero(prob):
prob.objective.set_sense(prob.objective.sense.minimize)
prob.linear_constraints.add(rhs = my_rhs, senses = my_sense,names = my_rownames)
prob.variables.add(obj = my_obj, ub = my_ub, lb = my_lb ,names = my_colnames)
rows = [0,1]
cols = [0,1]
vals = [20.0,30.0]
prob.linear_constraints.set_coefficients(zip(rows, cols, vals))
def lpex1():
try:
my_prob = cplex.Cplex()
handle = populatebynonzero(my_prob)
my_prob.solve()
except CplexError, exc:
print exc
return
numrows = my_prob.linear_constraints.get_num()
numcols = my_prob.variables.get_num()
print
# solution.get_status() returns an integer code
print "Solution status = " , my_prob.solution.get_status(), ":",
# the following line prints the corresponding string
print my_prob.solution.status[my_prob.solution.get_status()]
print "Solution value = ", my_prob.solution.get_objective_value()
slack = my_prob.solution.get_linear_slacks()
pi = my_prob.solution.get_dual_values()
x = my_prob.solution.get_values()
dj = my_prob.solution.get_reduced_costs()
for i in range(numrows):
print "Row %d: Slack = %10f Pi = %10f" % (i, slack[i], pi[i])
for j in range(numcols):
print "Column %d: Value = %10f Reduced cost = %10f" % (j, x[j], dj[j])
my_prob.write("lpex1.lp")
print x, "SOLUTIONS"
lpex1()
约束的行和列的定义有错误,下面的更正现在起作用
rows = [0,1,1]
cols = [0,1,2]
vals = [20.0,20.0,30.0]