Decoding the log file

[waltek001]

While the solver runs, it periodically updates with an improved solution. The corresponding line has a letter code that I presume indicates the methodology used to improve the solution. For example, here's a snippet showing R, but I've seen C and L as well:

Solving MIP model with:
   24768 rows
   322553 cols (2390 binary, 0 integer, 3 implied int., 320160 continuous)
   1631512 nonzeros

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work
     Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   -inf            inf                  inf        0      0      0         0     7.6s
         0       0         0   0.00%   -57099573.48275 inf                  inf        0      0      2    145773   127.4s
 R       0       0         0   0.00%   -57086550.97073 -56477184.59953    1.08%       32      1      2    146131   139.1s
         0       0         0   0.00%   -57078622.67195 -56477184.59953    1.06%       64      8      2    146725   147.6s

Is there any documentation that describes what these codes mean?

Cheers,
Karl

[jajhall]

In short, no, but I got to the bottom of them recently when working on the MIP solver. and here's a key

• B => Branching;
• C => Central rounding;
• F => Feasibility pump;
• H => Heuristic;
• I => Initial;
• L => Sub-MIP
• P => Empty MIP;
• R => Randomized rounding;
• S => Solve LP;
• T => Evaluate node;
• U => Unbounded;

To help decode this, but probably TMI, here are my detailed notes

bool HighsMipSolverData::addIncumbent(sol, solobj, source);

Use of source is only as the argument to HighsMipSolverData::printDisplayLine

When resolving the LP in HighsLpRelaxation

1281: source is ‘S’

When handling special cases in mip/HighsMipSolverData.cpp

79: Call from trySolution; source is passed in

bool HighsMipSolverData::trySolution computes the objective and row activities, returning false if the solution is not feasible, otherwise returns the truth of addIncumbent

trySolution is called from

    HighsLpRelaxation::run() if the node LP is unbounded; source is 'U'
    HighsPrimalHeuristics::solveSubMip when there is an optimal solution to a sub-MIP; source is 'L'

469: Call from runSetup when mipsolver.numCol() == 0; source is ‘P’

1361: Call from HighsMipSolverData::evaluateRootLp() when root node is optimal and has no fractional integers; source is ‘T’

When using primal heuristics (mip/HighsPrimalHeuristics.cpp)

879: Call from tryRoundedPoint; source is passed in

bool HighsPrimalHeuristics::tryRoundedPoint is called from bool HighsPrimalHeuristics::linesearchRounding, which is called from

    HighsPrimalHeuristics::centralRounding() with source 'C'
    HighsPrimalHeuristics::feasibilityPump() with source 'F'

1002: Call from randomizedRounding; source is ‘R’

1111: Call from feasibilityPump; source is ‘F’

When performing vanilla searches (mip/HighsSearch.cpp)

601: Call from selectBranchingCandidate; source is 'H' if inheuristic is true, otherwise 'B'

734: Call from selectBranchingCandidate; source is 'H' if inheuristic is true, otherwise 'B'

1064: Call from evaluateNode; source is 'H' if inheuristic is true, otherwise 'T'

[waltek001]

Perfect! Thank you!

K