Which Algorithm it is using for solving problem ? Is it Cutting Plane Method?

回答済み

Keerthi Selvan

2023年08月03日 07:12

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Gurobi 10.0.2 (win64) logging started Tue Aug  1 22:12:52 2023

Set parameter LogFile to value "gurobi_log.log"
Gurobi Optimizer version 10.0.2 build v10.0.2rc0 (win64)

CPU model: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, instruction set [SSE2|AVX|AVX2]
Thread count: 4 physical cores, 4 logical processors, using up to 4 threads

Optimize a model with 3533 rows, 2640 columns and 13250 nonzeros
Model fingerprint: 0xd6ff85c9
Variable types: 0 continuous, 2640 integer (0 binary)
Coefficient statistics:
  Matrix range     [1e+00, 1e+02]
  Objective range  [6e-01, 3e+01]
  Bounds range     [0e+00, 0e+00]
  RHS range        [4e+02, 1e+05]
Presolve removed 2640 rows and 24 columns
Presolve time: 0.01s
Presolved: 893 rows, 2616 columns, 7322 nonzeros
Variable types: 0 continuous, 2616 integer (0 binary)

Root relaxation: objective 1.139480e+08, 2527 iterations, 0.06 seconds (0.04 work units)

    Nodes    |    Current Node    |     Objective Bounds      |     Work
 Expl Unexpl |  Obj  Depth IntInf | Incumbent    BestBd   Gap | It/Node Time

     0     0 1.1395e+08    0  143          - 1.1395e+08      -     -    0s
H    0     0                    1.139481e+08 1.1395e+08  0.00%     -    0s

Cutting planes:
  Gomory: 8
  MIR: 2
  StrongCG: 5
  Zero half: 2

Explored 1 nodes (2578 simplex iterations) in 0.13 seconds (0.08 work units)
Thread count was 4 (of 4 available processors)

Solution count 1: 1.13948e+08 

Optimal solution found (tolerance 1.00e-04)
Best objective 1.139480513032e+08, best bound 1.139479808017e+08, gap 0.0001%

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  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:39

  This post is more than two 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.
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  Mario Ruthmair

  • Gurobi Staff

  2023年08月16日 10:21

  Hi Keerthi,

  The Gurobi solver uses multiple algorithms to solve a model involving presolving, branch-and-bound, adding cutting planes, heuristics, etc.
  In your case, the dual bound obtained from the root relaxation (relaxing integrality) is already the optimal value (under tolerances). Then, some heuristic found a primal solution with the same (optimal) objective value, leading to a zero gap. Some cutting planes have been added here and the branch-and-bound phase has not yet started.

  Best regards,
  Mario

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