Question

我已经建立了一个pyomo模型，并通过以下代码编写了该模型的lp文件：

# write LP file
filename = os.path.join(os.path.dirname(__file__), 'model.lp')
model.write(filename, io_options={'symbolic_solver_labels': True})

我在文件夹中得到model.lp文件。看起来像这样：

\* Source Pyomo model name=urbs *\

min 
obj:
+1 costs(Environmental)
+1 costs(Fixed)
+1 costs(Fuel)
+1 costs(Invest)
+1 costs(Variable)

s.t.

c_e_res_vertex(1_Mid_Biomass_Stock)_:
+1 e_co_stock(1_Mid_Biomass_Stock)
-1 e_pro_in(1_Mid_Biomass_plant_Biomass)
= 0

c_e_res_vertex(1_Mid_Coal_Stock)_:
+1 e_co_stock(1_Mid_Coal_Stock)
-1 e_pro_in(1_Mid_Coal_plant_Coal)
= 0

我的问题是，我还想保存模型的变量值。

是否有一种方法可以强制求解器将模型变量的值写入lp文件？

还是其他东西，以不同的方式做相同的事情？

Answer 1

我想到两种方法。

很好的旧搜索并替换

使用您的LP文件进行搜索并替换。例如，具有索引x和2（在Pyomo：'productA'中的索引model.x[2,'productA']的变量x(2_productA)被写为LP文件lpFileContent。知道这一点后，对于每个变量及其每个索引，以LP格式生成其名称，并在LP文件中搜索所有出现的这些变量，以它们的值替换它们。

如果for v in model.component_objects(Var, active=True): varName = str(v) varObject = getattr(model, varName) for index in varObject: indexStr = str(index) # Convert your index string: indexStr.replace(",","_") indexStr.replace(" ","_") indexStr.replace("'","") # Add more as you need. #Replace by value: lpFileContent.replace(varName + "(" + indexStr + ")", varObject[index].value) with open("output.txt", "w") as outputFile outputFile.write(lpFileContent)是您的LP文件中包含的字符串，则它将类似于：

model.A = RangeSet(1,10)
model.a = Param(model.A, within=PositiveReals)
model.ToBuy = Var(model.A)
def bud_rule(model, i):
    return model.a[i]*model.ToBuy[i] <= i
aBudget = Constraint(model.A, rule=bud_rule)

使用紧急情况

在定义约束时，通常以这种方式来实现（来自Pyomo doc）：

model.A = RangeSet(1,10)
model.a = Param(model.A, within=PositiveReals)
model.ToBuy = Var(model.A)
def bud_rule(model, i):
    print(str(model.a[i]*model.ToBuy[i]) + " <= " + str(i))
    return model.a[i]*model.ToBuy[i] <= i
aBudget = Constraint(model.A, rule=bud_rule)

然后，总是可以通过执行以下小技巧来检索此约束的表达式：

1 * model.ToBuy[1] <= 1
2 * model.ToBuy[2] <= 2
3 * model.ToBuy[3] <= 3
4 * model.ToBuy[4] <= 4
... #It goes on
10 * model.ToBuy[10] <= 10

将会产生类似

 import tkinter as tk
 from tkinter.filedialog 
 import askopenfilename
 import shutil
 import os
 from PIL import Image, ImageTk

 window = tk.Tk()

 window.title(" ")

  window.geometry("500x510")
  window.configure(background ="lightgreen")
  title = tk.Label(text="Click below to choose picture for testing disease....", background = "lightgreen", fg="Brown", font=("", 15))
  title.grid()
 def feature():
    window.destroy()
    window1 = tk.Tk()

    window1.title(" ")

    window1.geometry("650x510")
                      window1.configure(background="lightgreen")

      def exit():
             window1.destroy()
    #i want to print some features of image e.g. Mean, variance,s.d. Etc.
      button = tk.Button(text="Exit", command=exit)
      button.grid(column=0, row=9, padx=20, pady=20)

      window1.mainloop()


def openphoto():
    import cv2
    import numpy as np

    dirPath = " "
    fileList = os.listdir(dirPath)
    for fileName in fileList:
         os.remove(dirPath + "/" + fileName)

          fileName = askopenfilename(initialdir='', title='Select image for analysis ',
                       filetypes=[('image files', '.jpg')])
          dst = " "
          shutil.copy(fileName, dst)
          #this is the image
          Photo = Image.open(fileName)

          render = ImageTk.PhotoImage(photo)
          img = tk.Label(image=render, height="250", width="500")
          img.image = render
          img.place(x=0, y=0)
          img.grid(column=0, row=1, padx=10, pady = 10)
          title.destroy()
          button1.destroy()
          button2 = tk.Button(text="Analyse Image", command=feature)
         button2.grid(column=0, row=2, padx=10, pady = 10)
 button1 = tk.Button(text="Get Photo", command = openphoto)
 button1.grid(column=0, row=1, padx=10, pady = 10)
window.mainloop()

我相信这也是您可以使用的方法（通过搜索和替换，或者在解决之后再建立约束时打印变量值）。它赋予了自定义输出更多的功能，易于调试，但是如果表达式很长（例如对数千个元素求和的话）将非常慢。

具有可变值的Pyomo Model LP文件

1 个答案:

很好的旧搜索并替换

使用紧急情况