
From:  massimo scantamburlo 
Subject:  [Bugglpk] bugs 
Date:  Mon, 9 Dec 2002 11:52:35 +0100 
hi andrew. i'm an italian student and for my thesis
i'm workig with your glpk. first of all thank you for your work. i think it is a
very hard and big one. i've found some lacks so here they are (i use
microsoft VC++ 6.0 under winXP):
 in glplpt.c change of maximum lenght for a line
form 155 to 1155 (just a big value because i deal with very long
constraints)
 in glplpt.c change of maximum lenght for a token
image to catch variables with long name (from 16 to 160)
 i've noticed some wrong behaviours with integer
section parsing. i've changed the T_BINARY define setting to 66 (maybe
other likely defines can be wrong but i didn't test them yet)
 the parsing of the model is very sensitive to the
blank spaces or line feeds or some data card missing for mps files (Cplex read
them all with no problems), too restrictive because it doesn't support
definitions like lb<=constraint<=ub .
 many times the solver close with messages like
O : lpx_simplex: numerical instability
Assertion failed: spx_check_bbar(lp, lp>tol_bnd) == 0.0; file C:\glpk\glpk3.2. 2\source\glplpx6a.c; line 701 ======================================================
B : spx_invert: trying to factorize the basis using threshold tolerance 0.3 spx_invert: trying to factorize the basis using threshold tolerance 0.7 spx_invert: the basis matrix is singular lpx_simplex: numerical problems with basis matrix lpx_simplex: sorry, basis recovery procedure not implemented yet lpx_integer: optimal solution of LP relaxation required Sorry. Unable to find a start solution. Solver error code: 204. Elapsed time 1 (secs) Exiting... ======================================================
E: spx_invert: trying to factorize the basis using threshold tolerance
0.3
spx_invert: trying to factorize the basis using threshold tolerance 0.7 spx_invert: the basis matrix is singular lpx_simplex: numerical problems with basis matrix lpx_simplex: sorry, basis recovery procedure not implemented yet lpx_integer: optimal solution of LP relaxation required Sorry. Unable to find a start solution. Solver error code: 204. Elapsed time 36 (secs) Exiting... don't you think that could be more helpfull to set an infinite value for no
upper or lower bound than setting them to 0 when they are not defined?
i'll tell you everything else i'll find in future. if you already have some
updates please make me know. elsewhere i'll try to solve at least the simplest
problems. thank you very much.
Massimo Scantamburlo address@hidden 
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