纸浆线性整数优化

Question

在开始一个更大的问题之前，我试图做以下简单的优化问题示例。代码:

from pulp import *
x = LpVariable("x", 0, 3)
y = LpVariable("y", 0, 1)
prob = LpProblem("myProblem", LpMinimize)
prob += x + y <= 2
#objective function
prob += -4*x + y
status = prob.solve(GLPK(msg = 0))
#results
value(x)

我得到以下错误:

Traceback (most recent call last):
  File "C:UsersmahabubalamDesktopWorksGUIwhiskas.py", line 85, in <module>
    status = prob.solve(GLPK(msg = 0))
  File "C:Python34libsite-packagespulp-1.5.6-py3.4.eggpulppulp.py", line 1619, in solve
    status = solver.actualSolve(self, **kwargs)
  File "C:Python34libsite-packagespulp-1.5.6-py3.4.eggpulpsolvers.py", line 335, in actualSolve
    raise PulpSolverError("PuLP: cannot execute "+self.path)
pulp.solvers.PulpSolverError: PuLP: cannot execute glpsol.exe

谁能告诉我为什么会这样?

Answer 1

执行以下两步后，我已经成功运行了您的代码:

1. 从

   下载GLPK

   http://sourceforge.net/projects/winglpk/files/latest/download(如yyvind所述)

2. 解压缩到(例如):C:glpk_is_here

3. 在运行python之前将GLPK二进制文件添加到系统路径中C:>set PATH=%PATH%;C:glpk_is_hereglpk-4.55w64

4. 使用与(3)相同的cmd窗口，使用python/ipython来运行您的代码:
   C:>ipython your_code.py

5. 查看结果Out[4]: 2.0

好运。

Answer 2

当我在变量名中使用非法字符时，我得到了这个错误。从我在pulp的代码(确切地说是LpElement)中收集到的信息来看，字符-+[] ->/是不允许的，并且全部被下划线替换。

发现错误后，我使用以下函数预处理变量名，解决了这个问题:

  def variableName(s):
    # illegalChars = "-+[] ->/"
    s = s.replace("-","(hyphen)")
    s = s.replace("+","(plus)")
    s = s.replace("[","(leftBracket)")
    s = s.replace("]","(rightBracket)")
    s = s.replace(" ","(space)")
    s = s.replace(">","(greaterThan)")
    s = s.replace("/","(slash)")
    return s

Answer 3

这在unbuntu中适合我:

   sudo apt-get install python-glpk  
   sudo apt-get install glpk-utils

我想在windows中也有类似的解决方案

Answer 4

安装GLPK，例如从sourceforge.net/projects/winglpk

Answer 5

Mac - brew install glpk终端

Homebrew是最好的。