Segmentation fault when using openmp

[svigerske]

Issue created by migration from Trac.

Original creator: rbubley

Original creation time: 2015-02-03 17:14:24

Assignee: @tkralphs

Version: trunk (SVN)

I am running SYMPHONY 5.5.6 (Rev 2384), on a Mac, compiled with gcc (both version 4.8.4 and 4.9.2).

When running a MILP problem from the command line, I get a seg fault if I have compiled with OpenMP (and none if I have compiled without it).

The seg fault occurs after all the processing, and at the end of the output. Running it through a debugger, the offending line is line 819 of master_wrapper.c

It seg faults with -O3 and -O2 optimization flags, but didn't with -O0. It seems that it doesn't always seg fault, suggesting some sort of race condition, perhaps.

thread 1: tid = 0x53cd0b, 0x0000000100013219 symphony`free_master_u(env=0x0000000101002400) + 521 at master_wrapper.c:819, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xd4000000db)
    frame #0: 0x0000000100013219 symphony`free_master_u(env=0x0000000101002400) + 521 at master_wrapper.c:819
   816 	      if (env->warm_start->cuts){
   817 		 for (i = env->warm_start->cut_num - 1; i >= 0; i--){
   818 		    if (env->warm_start->cuts[i]){
-> 819 		       FREE(env->warm_start->cuts[i]->coef);
   820 		    }
   821 		    FREE(env->warm_start->cuts[i]);
   822 		 }

[svigerske]

Comment by @tkralphs created at 2015-02-03 17:23:53

Can you try just updating to SYMPHONY 5.6.6? I fixed a lot of bugs related to OpenMP between 5.5 and 5.6 (the difference between the two versions is mostly in the stability of the parallel mode).

[svigerske]

Comment by rbubley created at 2015-02-03 17:28:03

Apologies - that was a typo. I meant 5.6.6 not 5.5.6. I downloaded it fresh from svn this morning.

[svigerske]

Comment by @tkralphs created at 2015-02-03 17:46:36

OK, I will see if I can replicate this. Does it happen consistently with all problems or just with one? Did you run it through valgrind by chance?

[svigerske]

Comment by @tkralphs created at 2015-02-03 22:21:39

I have been able to replicate this seg fault. I will see what I can do. It seems to happen even with -p 0, which should be identical to the build without OpenMP.