cbc hangs and doesn't terminate on infeasible model even with `sec` and `maxN` set

[ssche]

I tried to run this model (see .mps, zipped), but cbc isn't returning when the termination conditions are reached (maximum nodes and maximum runtime).

Try to call cbc ./cbc-hangs.mps max presolve on sec 120 ratio 0.01 randomCbcSeed 42 randomSeed 42 allow 1 maxN 80000 integerTolerance 0.5 branch printingOptions all solution ./cbc-hangs.sol

Welcome to the CBC MILP Solver 
Version: 2.10.12 
Build Date: Aug 20 2024 

command line - ./cbc ./cbc-hangs.mps max presolve on sec 120 ratio 0.01 randomCbcSeed 42 randomSeed 42 allow 1 maxN 80000 integerTolerance 0.5 branch printingOptions all solution ./cbc-hangs.sol (default strategy 1)
At line 2 NAME          MODEL
At line 3 ROWS
At line 636 COLUMNS
At line 9373 RHS
At line 10005 BOUNDS
At line 10888 ENDATA
Problem MODEL has 631 rows, 882 columns and 6772 elements
Coin0008I MODEL read with 0 errors
seconds was changed from 1e+100 to 120
ratioGap was changed from 0 to 0.01
randomCbcSeed was changed from -1 to 42
randomSeed was changed from 1234567 to 42
allowableGap was changed from 1e-10 to 1
maxNodes was changed from 2147483647 to 80000
integerTolerance was changed from 1e-07 to 0.5
Continuous objective value is 1.66281e+09 - 0.00 seconds
Cgl0003I 0 fixed, 3 tightened bounds, 5 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 2 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 2 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0 substitutions
Cgl0004I processed model has 75 rows, 151 columns (151 integer (68 of which binary)) and 919 elements
Cbc0038I Initial state - 14 integers unsatisfied sum - 3.27769
Cbc0038I Pass   1: suminf.    3.28464 (14) obj. 1.41809e+09 iterations 5
Cbc0038I Pass   2: suminf.    3.02795 (13) obj. 1.34869e+09 iterations 2
Cbc0038I Solution found of 1.34869e+09
Cbc0038I Branch and bound needed to clear up 13 general integers
Cbc0038I Full problem 75 rows 151 columns, reduced to 59 rows 82 columns

Further observations:

• A call with sec 10 also hangs.
• CTRL+C doesn't terminate the process either.
• Highs solver returns immediately (default arguments, no mapping from the cbc command line call)

[jjhforrest]

master seems to work - will look into it.

[jjhforrest]

Have put a fix into stable. Will look further to see underlying problem.

[jjhforrest]

Interesting bug due to a defect in Osi. A basis is stored very compactly with just two bits per variable. This allows for free, basic, at lower bound and at upper bound. Superbasic i.e. not basic but between bounds is mapped to free. Superbasic variables are very very rare in branch and bound and normally there is no problem. Somehow primal got confused and looped.

Should be fixed - checking only adds a tiny amount of time.