The internal routine ios_solve_node was changed to retry solving the current subproblem with a new basis in case of simplex failure (mainly due to singularity of the basis matrix which, in turn, may happen due to inappropriate pivot choice). Thanks to Chris Matrakidis <[email protected]> for patch.
To fix the code please replace file glpk-4.58/src/glpios01.c with a new one (see attachment). Also attached is a model in free mps format that illustrates the effect. (This model looks "innocent", but it has some pathological properties that makes it very hard to solve with glpk.) Andrew Makhorin
glpios01.c.gz
Description: GNU Zip compressed data
water.mps.gz
Description: GNU Zip compressed data
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