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

Answered

Keerthi Selvan

August 03, 2023 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%

Related to

• MIP

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  Mario Ruthmair

  • Gurobi Staff

  August 16, 2023 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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