same model running twice using 48 and 32 threads, the first is infeasible and the other is feasible

回答済み

Muhammad ElSheikh

2020年08月19日 02:12

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Hi

I have run an  MIP model twice using 48 and 32 threads. I set "LazyConstraints=1" because I will use the callback to exclude some feasible solution.

my code:

from gurobipy import *
def mycallback(model, where):
  if where == GRB.Callback.MIPSOL:
    # Adding some lazy constraints
    pass

# The number of threads, 48 or 32
Threads = 48

m = read('model.lp')

# Set the number of threads
m.setParam("Threads", Threads)

# Set LazyConstraints = 1
m.setParam("LazyConstraints", 1)

m.optimize(mycallback)

if m.Status == 2:
  print("Find Solution")
  m.write('solution_%i_cores.sol' %Threads)
elif m.Status == 3:
  print("the model is infeasible")
else:
  print("Unkown Error")

The 48-thread run gave "Model is infeasible", however the 32-thread run gave a feasible solution.

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 03:08 編集済み

  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 why not try our AI Gurobot?.
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  Muhammad ElSheikh

  2020年08月19日 02:23

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  the MIP model: https://www.dropbox.com/s/l7t6cyqmfcusiom/model.lp?dl=0

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  Jaromił Najman

  • Gurobi Staff

  2020年08月26日 11:03

  Hi,

  I created a ticket on this issue. Please proceed in the ticket.

  Best regards,
  Jaromił

  1
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  Eli Towle

  • Gurobi Staff

  2020年11月06日 23:16

  This has been fixed in Gurobi 9.1, which is now available for download. Thanks for reporting the issue!

  0

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