[SCIP] MPS Read and Write and Structure Detection

["Büsing, Henrik"]

Dear SCIP users, 

 

I would like to read in an MPS-file, detect a possible arrowhead structure
via dec_hcgpartition.cpp and then write the MPS-file with the new structure.
I was able to read in an MPS-file and solve it, but I get a segmentation
fault while writing the MPS-file (see [2] for the code). When running in
debugger I get error [1].

Could you point out what I am doing wrong while trying to write the
MPS-file? 
Additionally, why is vars two-dimensional? Should this not be just a long
array with all the variables in it? How do I print the solution in a correct
way? A nested loop over i and j does not honor the sparse structure of the
constraint matrix A. 

Finally, is there an example on how to use the structure detection of GCG? 

 

Thank you very much for your help! 

Best, 
Henrik

 

 

[1]

Program received signal SIGSEGV, Segmentation fault.

SCIPreaderGetData (reader=reader at entry=0x0)

    at /home/henrik/Code/scipoptsuite-6.0.1/scip/src/scip/reader.c:488

488            return reader->readerdata;

 

[2]

// Derived from Queens example by Cornelius Schwarz

#include <scip/scip.h>

#include <scip/scipdefplugins.h>

#include "scip_exception.hpp"

#include <iostream>

 

using namespace std;

 

 

/** main function **/

int

main()

{

   // Define scip pointer and filename

   SCIP* scip;

   SCIP_READER* reader;

   const char* filename="/home/henrik/JSC/FINE_exampleMpsFiles/toy.MPS";

   cout << filename  << endl;

   SCIP_RESULT* result;

   result = new SCIP_RESULT[3];

 

   // Create scip environment

   SCIP_CALL_EXC(SCIPcreate(& scip));

 

   // Load desired plugins

   SCIP_CALL_EXC(SCIPincludeDefaultPlugins(scip));

 

   // disable scip output to stdout

   SCIPmessagehdlrSetQuiet(SCIPgetMessagehdlr(scip), TRUE);

 

   // Read in *.MPS file

   SCIPreadMps(scip, reader, filename, result, 

               NULL,NULL,

                NULL,NULL, 

               NULL,NULL

                      );

   // Solve

   SCIP_CALL_EXC(SCIPsolve(scip));

 

   // Display solution

   SCIP_VAR** vars;

   vars  = SCIPgetVars(scip);

   SCIP_SOL* sol;

   sol = SCIPgetBestSol(scip);

 

   for (int i=0; i<3; ++i)

     for (int j=0; j<3; ++j)

   {

     cout << "Solution: " << SCIPgetSolVal(scip, sol, &vars[i][j]) << endl;

   }

 

   int nvars = SCIPgetNVars(scip); 

   int nbinvars = SCIPgetNBinVars(scip);

   int nintvars = SCIPgetNIntVars(scip);

   int nimplvars = SCIPgetNImplVars(scip); 

   int ncontvars =  SCIPgetNContVars(scip);

   SCIP_Real objscale = 1.0;

   SCIP_Real objoffset = 0.0;

   SCIP_VAR** fixedvars = SCIPgetFixedVars(scip);

   int nfixedvars =  SCIPgetNFixedVars(scip);

   SCIP_CONS** conss = SCIPgetConss(scip);

   int nconss = SCIPgetNConss(scip); 

   const char* name="Toy"; 

 

   SCIPwriteMps(scip, reader, NULL, name, FALSE, SCIP_OBJSENSE_MINIMIZE,

                               objscale, objoffset, vars, nvars, nbinvars,
nintvars,

                               nimplvars, ncontvars, fixedvars, nfixedvars,
conss,

                               nconss, result

                );

 

   return EXIT_SUCCESS;

}

-- 

Dipl.-Math. Henrik Büsing

Jülich Supercomputing Centre

Institute for Advanced Simulation

 

Forschungszentrum Jülich

Wilhelm-Johnen-Straße

52425 Jülich, Germany

 

Phone:  +49-2461-61-9884

Fax:    +49-2461-61-6656

E-Mail: H.Buesing at fz-juelich.de

WWW:    http://www.fz-juelich.de/ias/jsc

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Forschungszentrum Juelich GmbH

52425 Juelich

Sitz der Gesellschaft: Juelich

Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498

Vorsitzender des Aufsichtsrats: MinDir Volker Rieke

Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender),

Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt,

Prof. Dr. Sebastian M. Schmidt

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