Re: [Help-glpk] MPS model has zero objective function in version 4_32

[Jack Franklin]

Hi, 

I need to read mps file and then call glpk(c, a, b, lb, ub, ctype, vartype,
sense, param) .

In the mps files of MIPLIB, the MIP problems are not standard form , now I
need to reform it so
that the glpk can get correct input arguments for (c, a, b, lb, ub, ctype,
vartype, sense, param).

I have very large matrix , so how to load these data for glpk such that I
can get input arguments for

function [xopt, fmin, status, extra] = glpk (c, a, b, lb, ub, ctype,
vartype, sense, param)

How to transform the MIP to standard forms such that glpk can solve it ?

Because I need to do some modifications on the original MIP problems , I
need to get
its components such as constrain matrix so that I can change it for the
following operations.


Jack

Nov.  29  2008 


Marc Goetschalckx wrote:
> 
> I am writing an identical GLPK problem out in MPS format and LP format 
> from the API.  I then read and solve the models with glpsol.  The LP 
> model solves correctly.  The MPS model solves but has objective function 
> zero.  A similar behavior occurred in earlier version unless the 
> parameter LPS_K_MPSOBJ was set to 1.  However, the function 
> lpx_set_int_parm is no longer available in version 4.32.  How do I 
> specify the objective function in the MPS model with version 4_32 (and I 
> assume the current version as well).  The following lines are the output 
> of the LP and the MPS models solved with glpsol.
> Thanks
> 
> glpsol_4_32 --freemps VRP100_best.mps
> glp_read_mps: reading problem data from `VRP100_best.mps'...
> glp_read_mps: problem VRP100_Best
> glp_read_mps: 102 rows, 9 columns, 108 non-zeros
> glp_read_mps: 8 integer columns, all of which are binary
> glp_read_mps: 232 records were read
> ipp_basic_tech:  102 row(s) and 9 column(s) removed
> ipp_reduce_bnds: 1 pass(es) made, 0 bound(s) reduced
> ipp_basic_tech:  0 row(s) and 0 column(s) removed
> ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
> Objective value = 0
> INTEGER OPTIMAL SOLUTION FOUND BY MIP PRESOLVER
> Time used:   0.0 secs
> Memory used: 0.1 Mb (61348 bytes)
> 
> glpsol_4_32 --cpxlp VRP100_best.lp
> glp_read_lp: reading problem data from `VRP100_best.lp'...
> glp_read_lp: 101 rows, 9 columns, 108 non-zeros
> glp_read_lp: 8 integer columns, all of which are binary
> glp_read_lp: 134 lines were read
> ipp_basic_tech:  101 row(s) and 9 column(s) removed
> ipp_reduce_bnds: 1 pass(es) made, 0 bound(s) reduced
> ipp_basic_tech:  0 row(s) and 0 column(s) removed
> ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
> Objective value = 113800.9085
> INTEGER OPTIMAL SOLUTION FOUND BY MIP PRESOLVER
> Time used:   0.0 secs
> Memory used: 0.1 Mb (53324 bytes)
> 
> 
> 
> _______________________________________________
> Help-glpk mailing list
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> http://lists.gnu.org/mailman/listinfo/help-glpk
> 
> 

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