1: #include <petsc/private/matimpl.h>      /*I "petscmat.h"  I*/
  2: #include <petscsf.h>

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

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

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

 49:   /* determine the number of entries in the column matrix */
 50:   PetscLogEventBegin(Mat_Coloring_Comm,*etoc,0,0,0);
 51:   PetscSFComputeDegreeBegin(*etoc,&coldegrees);
 52:   PetscSFComputeDegreeEnd(*etoc,&coldegrees);
 53:   PetscLogEventEnd(Mat_Coloring_Comm,*etoc,0,0,0);
 54:   ncolentries=0;
 55:   for (i=0;i<cn;i++) {
 56:     ncolentries += coldegrees[i];
 57:   }
 58:   PetscMalloc1(ncolentries,&colleaf);

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

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

 70:   PetscLogEventBegin(Mat_Coloring_Comm,*etor,0,0,0);
 71:   PetscSFComputeDegreeBegin(*etor,&rowdegrees);
 72:   PetscSFComputeDegreeEnd(*etor,&rowdegrees);
 73:   PetscLogEventEnd(Mat_Coloring_Comm,*etor,0,0,0);

 75:   PetscFree(rowdata);
 76:   PetscFree(rowleaf);
 77:   PetscFree(colleaf);
 78:   return(0);
 79: }