Actual source code: bipartite.c
petsc-3.10.5 2019-03-28
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      1:  #include <petsc/private/matimpl.h>
      2:  #include <petscsf.h>

      4: PETSC_EXTERN PetscErrorCode MatColoringCreateBipartiteGraph(MatColoring mc,PetscSF *etoc,PetscSF *etor)
      5: {
      6:   PetscErrorCode    ierr;
      7:   PetscInt          nentries,ncolentries,idx;
      8:   PetscInt          i,j,rs,re,cs,ce,cn;
      9:   PetscInt          *rowleaf,*colleaf,*rowdata;
     10:   PetscInt          ncol;
     11:   const PetscScalar *vcol;
     12:   const PetscInt    *icol;
     13:   const PetscInt    *coldegrees,*rowdegrees;
     14:   Mat               m = mc->mat;

     17:   MatGetOwnershipRange(m,&rs,&re);
     18:   MatGetOwnershipRangeColumn(m,&cs,&ce);
     19:   cn = ce-cs;
     20:   nentries=0;
     21:   for (i=rs;i<re;i++) {
     22:     MatGetRow(m,i,&ncol,NULL,&vcol);
     23:     for (j=0;j<ncol;j++) {
     24:       nentries++;
     25:     }
     26:     MatRestoreRow(m,i,&ncol,NULL,&vcol);
     27:   }
     28:   PetscMalloc1(nentries,&rowleaf);
     29:   PetscMalloc1(nentries,&rowdata);
     30:   idx=0;
     31:   for (i=rs;i<re;i++) {
     32:     MatGetRow(m,i,&ncol,&icol,&vcol);
     33:     for (j=0;j<ncol;j++) {
     34:       rowleaf[idx] = icol[j];
     35:       rowdata[idx] = i;
     36:       idx++;
     37:     }
     38:     MatRestoreRow(m,i,&ncol,&icol,&vcol);
     39:   }
     40:   if (idx != nentries) SETERRQ2(PetscObjectComm((PetscObject)m),PETSC_ERR_NOT_CONVERGED,"Bad number of entries %d vs %d",idx,nentries);
     41:   PetscSFCreate(PetscObjectComm((PetscObject)m),etoc);
     42:   PetscSFCreate(PetscObjectComm((PetscObject)m),etor);

     44:   PetscSFSetGraphLayout(*etoc,m->cmap,nentries,NULL,PETSC_COPY_VALUES,rowleaf);
     45:   PetscSFSetFromOptions(*etoc);

     47:   /* determine the number of entries in the column matrix */
     48:   PetscLogEventBegin(MATCOLORING_Comm,*etoc,0,0,0);
     49:   PetscSFComputeDegreeBegin(*etoc,&coldegrees);
     50:   PetscSFComputeDegreeEnd(*etoc,&coldegrees);
     51:   PetscLogEventEnd(MATCOLORING_Comm,*etoc,0,0,0);
     52:   ncolentries=0;
     53:   for (i=0;i<cn;i++) {
     54:     ncolentries += coldegrees[i];
     55:   }
     56:   PetscMalloc1(ncolentries,&colleaf);

     58:   /* create the one going the other way by building the leaf set */
     59:   PetscLogEventBegin(MATCOLORING_Comm,*etoc,0,0,0);
     60:   PetscSFGatherBegin(*etoc,MPIU_INT,rowdata,colleaf);
     61:   PetscSFGatherEnd(*etoc,MPIU_INT,rowdata,colleaf);
     62:   PetscLogEventEnd(MATCOLORING_Comm,*etoc,0,0,0);

     64:   /* this one takes mat entries in *columns* to rows -- you never have to actually be able to order the leaf entries. */
     65:   PetscSFSetGraphLayout(*etor,m->rmap,ncolentries,NULL,PETSC_COPY_VALUES,colleaf);
     66:   PetscSFSetFromOptions(*etor);

     68:   PetscLogEventBegin(MATCOLORING_Comm,*etor,0,0,0);
     69:   PetscSFComputeDegreeBegin(*etor,&rowdegrees);
     70:   PetscSFComputeDegreeEnd(*etor,&rowdegrees);
     71:   PetscLogEventEnd(MATCOLORING_Comm,*etor,0,0,0);

     73:   PetscFree(rowdata);
     74:   PetscFree(rowleaf);
     75:   PetscFree(colleaf);
     76:   return(0);
     77: }