Re: [Bug-glpk] glp_intopt recovery feature added

[Sascha Brügmann]

Am 21.02.2016 um 22:57 schrieb Chris Matrakidis:
> With glpk compiled using "-O1 -msse3 -mfpmath=sse" on a 32 bit system
> with gcc 4.6.1 and running:
> glpsol --bestp --nointopt water.mps
> I was able to reproduce an error that was reported earlier:
> http://lists.gnu.org/archive/html/bug-glpk/2016-01/msg00000.html
>
> The last lines of output were:
> Integer optimization begins...
> +   198: mip =     not found yet >=              -inf        (1; 0)
> Error: unable to factorize the basis matrix (1)
> Constructing initial basis...
> Size of triangular part is 521
> + 23751: mip =     not found yet >=  8.372570868e+004        (916; 2246)
> + 49757: mip =     not found yet >=  8.372570868e+004        (1518; 4753)
> + 75846: mip =     not found yet >=  8.372570868e+004        (2031; 7453)
> Assertion failed: tcol[csa->p] != 0.0
> Error detected in file simplex/spydual.c at line 999
Yeah!!! Since posting my issue i've collected at least two LPs which let 
GLPK crash with this error. The bad thing is that the crash only occures 
when I call GLPK from my Java-application via java-glpk. Writing the 
completely created LP to disk with glp_write_prob() and letting glpsol 
int-opt the LP, with apparently the same parameters as used in my Java 
application, never caused the crash. Made me crazy not being able to 
reproduce the problem in a viable manner. I'm so glad you found an LP to 
reproduce!

The cycling I have noticed too, but it occues much less than the spydual 
crash in my cases and i wasn't able to collect causing LPs.