Wrong result with current master build

[christoph-cullmann]

Reference result with older version and cplex is 6497547.
value_6497547.lp.txt.gz

/local/ssd/cullmann/build/lpsolve.clpsolve/usr/bin/cbc test/value_6497547.lp
Welcome to the CBC MILP Solver
Version: trunk
Build Date: Feb 15 2024
command line - test/value_6497547.lp (default strategy 1)
 CoinLpIO::readLp(): Maximization problem reformulated as minimization
Coin0009I Switching back to maximization to get correct duals etc
Continuous objective value is 6.49764e+06 - 0.710382 seconds
Cgl0003I 0 fixed, 752 tightened bounds, 89 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 1288 tightened bounds, 666 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 256 tightened bounds, 85 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 858 tightened bounds, 200 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 550 tightened bounds, 135 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 915 tightened bounds, 187 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 540 tightened bounds, 156 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 1182 tightened bounds, 291 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 268 tightened bounds, 105 strengthened rows, 0 substitutions
Cgl0004I processed model has 3982 rows, 4112 columns (4112 integer (1678 of which binary)) and 13840 elements
Coin3009W Conflict graph built in 0.000 seconds, density: 0.017%
Cgl0015I Clique Strengthening extended 0 cliques, 0 were dominated
Cbc0038I Initial state - 3 integers unsatisfied sum - 0.9
Cbc0038I Solution found of 6.44484e+06
Cbc0038I Branch and bound needed to clear up 3 general integers
Cbc0038I Full problem 3982 rows 4112 columns, reduced to 375 rows 397 columns
Cbc0038I Cleaned solution of 6.44482e+06
Cbc0038I Before mini branch and bound, 4109 integers at bound fixed and 0 continuous of which 122 were internal integer and 0 internal continuous
Cbc0038I Full problem 3982 rows 4112 columns, reduced to 0 rows 0 columns
Cbc0038I Mini branch and bound did not improve solution (2.76 seconds)
Cbc0038I Round again with cutoff of 6.44482e+06
Cbc0038I Reduced cost fixing fixed 1772 variables on major pass 2
Cbc0038I Solution found of 6.44484e+06
Cbc0038I Branch and bound needed to clear up 3 general integers
Cbc0038I Full problem 3983 rows 4112 columns, reduced to 58 rows 71 columns
Cbc0038I Mini branch and bound could not fix general integers
Cbc0038I No solution found this major pass
Cbc0038I Before mini branch and bound, 4109 integers at bound fixed and 0 continuous of which 122 were internal integer and 0 internal continuous
Cbc0038I Mini branch and bound did not improve solution (3.11 seconds)
Cbc0038I After 3.13 seconds - Feasibility pump exiting with objective of 6.44482e+06 - took 0.77 seconds
Cbc0012I Integer solution of 6444821 found by feasibility pump after 0 iterations and 0 nodes (3.13 seconds)
Cbc0038I Full problem 3982 rows 4112 columns, reduced to 6 rows 9 columns
Cbc0031I 8 added rows had average density of 7.75
Cbc0013I At root node, 26 cuts changed objective from 6444842 to 6444821 in 2 passes
Cbc0014I Cut generator 0 (Probing) - 0 row cuts average 0.0 elements, 196 column cuts (196 active)  in 0.004 seconds - new frequency is 1
Cbc0014I Cut generator 1 (Gomory) - 12 row cuts average 8.2 elements, 0 column cuts (0 active)  in 0.001 seconds - new frequency is 1
Cbc0014I Cut generator 2 (Knapsack) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.002 seconds - new frequency is -100
Cbc0014I Cut generator 3 (Clique) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.000 seconds - new frequency is -100
Cbc0014I Cut generator 4 (OddWheel) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.004 seconds - new frequency is -100
Cbc0014I Cut generator 5 (MixedIntegerRounding2) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.001 seconds - new frequency is -100
Cbc0014I Cut generator 6 (FlowCover) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.000 seconds - new frequency is -100
Cbc0014I Cut generator 7 (TwoMirCuts) - 17 row cuts average 7.3 elements, 0 column cuts (0 active)  in 0.002 seconds - new frequency is -100
Cbc0001I Search completed - best objective 6444821, took 6 iterations and 0 nodes (3.42 seconds)
Cbc0035I Maximum depth 0, 849 variables fixed on reduced cost
Cuts at root node changed objective from 6.44484e+06 to 6.44482e+06
Probing was tried 2 times and created 196 cuts (0.004435 seconds)
Gomory was tried 2 times and created 12 cuts (0.001218 seconds)
Knapsack was tried 2 times and created 0 cuts (0.00179 seconds)
Clique was tried 2 times and created 0 cuts (0.000151 seconds)
OddWheel was tried 2 times and created 0 cuts (0.004066 seconds)
MixedIntegerRounding2 was tried 2 times and created 0 cuts (0.000943 seconds)
FlowCover was tried 2 times and created 0 cuts (0.000369 seconds)
TwoMirCuts was tried 2 times and created 17 cuts (0.001718 seconds)
ZeroHalf was tried 1 times and created 0 cuts (0.004177 seconds)
Cgl0014I Postprocessing changed objective from 6444821 to 6455513 - possible tolerance issue - try without preprocessing

Result - Optimal solution found
Objective value:                6455513
Enumerated nodes:               0
Total iterations:               6
Time (CPU seconds):             4.14164
Time (Wallclock seconds):       4.60015
Total time (CPU seconds):       4.91778   (Wallclock seconds):       5.44593

[jjhforrest]

Looks like a change to CoinPresolveDupcol.cpp is the culprit - all was OK when I copied that over from stable. Should be able to get it fixed by Monday.

[jjhforrest]

There is some very complicated code in CoinPresolveDupcol.cpp which flips signs all over the place. I know from experience how easy it is to get one of the cases wrong. I have modified so that it does not try as hard. If the author of the changes can fix - then good.

[christoph-cullmann]

Current master looks fine for this example.