from __future__ import division
from pyomo.environ import *
model = ConcreteModel()
model.x = Var([1,2], domain=NonNegativeReals)
model.OBJ = Objective(expr = 2*model.x[1] + 3*model.x[2])
model.Constraint1 = Constraint(expr = 3*model.x[1] + 4*model.x[2] >= 1)

我执行：

> pyomo solve Pyomo_concrete_v1.py --solver=glpk

根据我自己的计算，结果应该是：

x[1]=0
x[2]=0.25
OBJ=0.75

然而，我发现以下结果。yml'：

# ----------------------------------------------------------
#   Problem Information
# ----------------------------------------------------------
Problem: 
- Name: unknown
  Lower bound: 0.666666666667
  Upper bound: 0.666666666667
  Number of objectives: 1
  Number of constraints: 2
  Number of variables: 3
  Number of nonzeros: 3
  Sense: minimize
# ----------------------------------------------------------
#   Solver Information
# ----------------------------------------------------------
Solver: 
- Status: ok
  Termination condition: optimal
  Statistics: 
    Branch and bound: 
      Number of bounded subproblems: 0
      Number of created subproblems: 0
  Error rc: 0
  Time: 0.018000125885
# ----------------------------------------------------------
#   Solution Information
# ----------------------------------------------------------
Solution: 
- number of solutions: 1
  number of solutions displayed: 1
- Gap: 0.0
  Status: feasible
  Message: None
  Objective:
    OBJ:
      Value: 0.666666666667
  Variable:
    x[1]:
      Value: 0.333333333333
  Constraint: No values

我不明白为什么会有“2个约束”（实际上只有一个约束）、“3个变量”（实际上是2），结果是一个大小为1的向量。

这个results.yml每次执行pyomo时都会更改，但内容总是相同的。