How to output all feasible solutions?

Answered

FEI XUE

May 24, 2022 01:11

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from gurobipy import *
import numpy as np
import math
space=gurobipy.Model('matchpattern')
n=6
pij=space.addVars(range(1,n+1), range(1,n+1),vtype=gurobipy.GRB.BINARY)

space.update()
space.setObjective(quicksum(pij[i,j] for i in range (1,n+1) for j in range(1,n+1)),GRB.MINIMIZE)

space.addConstrs(quicksum(pij[i,j] for i in range(1,n+1))==1 for j in range(1,n+1))
space.addConstrs(quicksum(pij[i,j] for j in range(1,n+1))==1 for i in range(1,n+1))

space.addConstrs(pij[i,j]==pij[j,i] for i in range (1,n+1) for j in range(1,n+1))
space.addConstrs(pij[i,i]==0 for i in range (1,n+1))

space.optimize()

 

Here is my code, when n is 6, there should be 15 possible solutions, how can I output all 15 possible solutions as a matrix like this?

Looking forward your reply. Thank you very much.

([[[0,1,0,0,0,0],[1,0,0,0,0,0],[0,0,0,1,0,0],[0,0,1,0,0,0],[0,0,0,0,0,1],[0,0,0,0,1,0]],\
               [[0,1,0,0,0,0],[1,0,0,0,0,0],[0,0,0,0,1,0],[0,0,0,0,0,1],[0,0,1,0,0,1],[0,0,0,1,0,0]],\
               [[0,1,0,0,0,0],[1,0,0,0,0,0],[0,0,0,0,0,1],[0,0,0,0,1,0],[0,0,0,1,0,0],[0,0,1,0,0,0]],\
               [[0,0,1,0,0,0],[0,0,0,1,0,0],[1,0,0,0,0,0],[0,1,0,0,0,0],[0,0,0,0,0,1],[0,0,0,0,1,0]],\
               [[0,0,1,0,0,0],[0,0,0,0,1,0],[1,0,0,0,0,0],[0,0,0,0,0,1],[0,1,0,0,0,0],[0,0,0,1,0,0]],\
               [[0,0,1,0,0,0],[0,0,0,0,0,1],[1,0,0,0,0,0],[0,0,0,0,1,0],[0,0,0,1,0,0],[0,1,0,0,0,0]],\
               [[0,0,0,1,0,0],[0,0,1,0,0,0],[0,1,0,0,0,0],[1,0,0,0,0,0],[0,0,0,0,0,1],[0,0,0,0,1,0]],\
               [[0,0,0,1,0,0],[0,0,0,0,1,0],[0,0,0,0,0,1],[1,0,0,0,0,0],[0,1,0,0,0,0],[0,0,1,0,0,0]],\
               [[0,0,0,1,0,0],[0,0,0,0,0,1],[0,0,0,0,1,0],[1,0,0,0,0,0],[0,0,1,0,0,0],[0,1,0,0,0,0]],\
               [[0,0,0,0,1,0],[0,0,1,0,0,0],[0,1,0,0,0,0],[0,0,0,0,0,1],[1,0,0,0,0,0],[0,0,0,1,0,0]],\
               [[0,0,0,0,1,0],[0,0,0,1,0,0],[0,0,0,0,0,1],[0,1,0,0,0,0],[1,0,0,0,0,0],[0,0,1,0,0,0]],\
               [[0,0,0,0,1,0],[0,0,0,0,0,1],[0,0,0,1,0,0],[0,0,1,0,0,0],[1,0,0,0,0,0],[0,1,0,0,0,0]],\
               [[0,0,0,0,0,1],[0,0,1,0,0,0],[0,1,0,0,0,0],[0,0,0,0,1,0],[0,0,0,1,0,0],[1,0,0,0,0,0]],\
               [[0,0,0,0,0,1],[0,0,0,1,0,0],[0,0,0,0,1,0],[0,1,0,0,0,0],[0,0,1,0,0,0],[1,0,0,0,0,0]],\
               [[0,0,0,0,0,1],[0,0,0,0,1,0],[0,0,0,1,0,0],[0,0,1,0,0,0],[0,1,0,0,0,0],[1,0,0,0,0,0]]])

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 16, 2025 23:36

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
• 

  Jonasz Staszek

  • Community Moderator

  May 25, 2022 12:51

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  If you know upfront that there will be 15 solutions, you can add these two lines before the optimize call:

  space.setParam("PoolSolutions", 15)
  space.setParam("PoolSearchMode", 2)

  Further info can be found here.

  Best regards,
  Jonasz

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  FEI XUE

  May 28, 2022 12:59

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  Doctor Jonasz

  Thank you very much.

  It helps me a lot.

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