CBC gets stuck after fixing variables

[sebheger]

When solving the attached model.lp.zip on Mac OS 10.15.4 with CBC 2.10.3 installed via brew, the optimizer gets stuck after the root relaxation when variables are fixed. It is not crashing but after several hours nothing happens (might be an endless loop or something, ...) Would you please check that behavior, as gurobi for example solves this problem in under 2 minutes.

Welcome to the CBC MILP Solver
Version: 2.10.3
Build Date: May 26 2020

command line - cbc model.lp (default strategy 1)
Continuous objective value is 368.615 - 301.35 seconds
Cgl0002I 1369 variables fixed

[jjhforrest]

Sebastian,

Will look at it. It is a very easy problem! - just very large. I think there are two reasons why it takes so long. One is that probing in pre-processing will take a long time, so I will see if there is an easy way to say whether to switch off probing.

The more serious - and at the moment more mysterious problem is that after Cbc makes a few changes to tighten the problem, the LP resolve takes a very very long time.

cbc model.lp -duals -cgraph off -cuts off -preprocess off -solve

solves it in a few minutes!