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From: | Joey Rios |
Subject: | [Help-glpk] Print names of all rows after presolve? |
Date: | Fri, 20 Jun 2008 17:13:58 -0700 |
I am debugging the code I plan to use to generate cplex-format input files. I am comparing my generated files to my "gold standard" which is a MathProg model. I provide the MathProg model to glpsol and write out a cplex translation to compare against my directly-generated cplex file. I am at the point where I can't do much more debugging through text-parsing tools (sed, awk, etc.). I would love to see a list of row names that glpk finds after the presolve. Here is why: Output from my directly generated cplex file: ... lpx_read_cpxlp: 504148 rows, 299500 columns, 1096954 non-zeros lpx_read_cpxlp: 299500 integer columns, all of which are binary lpx_read_cpxlp: 1128550 lines were read glp_simplex: original LP has 504148 rows, 299500 columns, 1096954 non-zeros glp_simplex: presolved LP has 504148 rows, 299500 columns, 1096954 non-zeros lpx_adv_basis: size of triangular part = 504148 0: objval = 0.000000000e+00 infeas = 1.000000000e+00 (0) ... And here is the output from my reference model: ... lpx_read_cpxlp: 547545 rows, 302843 columns, 1418415 non-zeros lpx_read_cpxlp: 302843 integer columns, all of which are binary lpx_read_cpxlp: 1851799 lines were read glp_simplex: original LP has 547545 rows, 302843 columns, 1418415 non-zeros glp_simplex: presolved LP has 504162 rows, 299500 columns, 1097272 non-zeros lpx_adv_basis: size of triangular part = 504162 0: objval = 0.000000000e+00 infeas = 1.000000000e+00 (0) ... So for my directly generated model I am trying to do my own "presolving" (in a sense) by avoiding generation of trivial rows/cols. You can see that I am producing 14 too few rows (504162 - 504148) in my directly generated cplex file. Oh, how I'd love to know the names of those rows. Any thoughts on how to tease those out? I am fine using the API. It seems that the presolver is too much of a "black box" to get at via the API? Ideally before the phase I simplex takes over but after the presolver, I'd like to dump that column name info. Will I have to hack into the source to do this? Any suggestions appreciated. I can provide more info if it's helpful. Thanks in advance, Joey Earn cashback on your purchases with Live Search - the search that pays you back! Learn More |
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