RE: [Help-glpk] Getting more info from presolver

[Joey Rios]

> You may look at the output listing produced by either glpsol (with

> -o option) or the api routine lpx_print_sol.

It was actually more economical for me to go to the source code on this.  In the time it would take glpsol to provide the KKT info (several hours), I threw some lines into glpk and got the info I needed.  Of course, I have no idea if what I added will break other things or will work for all cases, it just gave me what I needed.  For completeness of this discussion thread, here is the message I was receiving originally:

lpx_read_cpxlp: reading problem data from `dw_monolithic.cplex'...
lpx_read_cpxlp: 440350 rows, 299500 columns, 969398 non-zeros
lpx_read_cpxlp: 299500 integer columns, all of which are binary
lpx_read_cpxlp: 1089422 lines were read
glp_simplex: original LP has 440350 rows, 299500 columns, 969398 non-zeros
PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION
glp_intopt: optimal basis to initial LP relaxation not provided
Time used:   1.0 secs
Memory used: 211.3 Mb (221541952 bytes)


And with less than 10-20 lines of additional code I could get this:


lpx_read_cpxlp: reading problem data from `dw_monolithic.cplex'...
lpx_read_cpxlp: 440350 rows, 299500 columns, 969398 non-zeros
lpx_read_cpxlp: 299500 integer columns, all of which are binary
lpx_read_cpxlp: 1089422 lines were read
glp_simplex: original LP has 440350 rows, 299500 columns, 969398 non-zeros
General Row Analysis.  Row 437495.
PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION
The problem row was 437495, DepartCap(CLE,2).
glp_intopt: optimal basis to initial LP relaxation not provided
Time used:   0.0 secs
Memory used: 211.3 Mb (221541956 bytes)


This is going to help me debug my code for generating my input file to glpsol.  I'd be happy to send you my changes, Andrew, if you thought it would be helpful.  They seem very minor, but again, I can't say I've considered every implication of their inclusion.

Joey

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