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[Bug-glpk] bug in spx_prim_chuzr and solution
From: |
Kiriakos Vlahos |
Subject: |
[Bug-glpk] bug in spx_prim_chuzr and solution |
Date: |
Sun, 6 Oct 2002 02:55:57 +0100 |
I found a rather rare bug in spx_prim_chuzr.
If all elements of the q-th column of the simplex table are too small,
ret is set to 1 to tell the calling routine to reinvert the basis (which
is currently not implemented and causes an error).
But if (typx[k] == LPX_DB) this is OK and should not cause concern.
I suggest the following modification at line 740:
if (typx[k] == LPX_DB)
{ /* xN[q] has both lower and upper bounds */
p = -1, p_tag = 0, teta = (ub[k] - lb[k]) + relax, big = 1.0;
ret = 0; //<- added line
}
This logic error may exist in similar routines used in the dual variant
of the simplex method but I have not checked. I came across it while
solving a very simple problem with one constraint!
Many thanks
Kiriakos Vlahos
- [Bug-glpk] bug in spx_prim_chuzr and solution,
Kiriakos Vlahos <=