2: #include <petscmat.h>
  3: #include <petsc-private/matorderimpl.h>

  5: /*
  6:     MatGetOrdering_QMD - Find the Quotient Minimum Degree ordering of a given matrix.
  7: */
 10: PETSC_EXTERN PetscErrorCode MatGetOrdering_QMD(Mat mat,MatOrderingType type,IS *row,IS *col)
 11: {
 12:   PetscInt       i,  *deg,*marker,*rchset,*nbrhd,*qsize,*qlink,nofsub,*iperm,nrow,*perm;
 14:   const PetscInt *ia,*ja;
 15:   PetscBool      done;

 18:   MatGetRowIJ(mat,1,PETSC_TRUE,PETSC_TRUE,&nrow,&ia,&ja,&done);
 19:   if (!done) SETERRQ(PetscObjectComm((PetscObject)mat),PETSC_ERR_SUP,"Cannot get rows for matrix");

 21:   PetscMalloc1(nrow,&perm);
 22:   PetscMalloc5(nrow,&iperm,nrow,&deg,nrow,&marker,nrow,&rchset,nrow,&nbrhd);
 23:   PetscMalloc2(nrow,&qsize,nrow,&qlink);
 24:   /* WARNING - genqmd trashes ja */
 25:   SPARSEPACKgenqmd(&nrow,ia,ja,perm,iperm,deg,marker,rchset,nbrhd,qsize,qlink,&nofsub);
 26:   MatRestoreRowIJ(mat,1,PETSC_TRUE,PETSC_TRUE,NULL,&ia,&ja,&done);

 28:   PetscFree2(qsize,qlink);
 29:   PetscFree5(iperm,deg,marker,rchset,nbrhd);
 30:   for (i=0; i<nrow; i++) perm[i]--;
 31:   ISCreateGeneral(PETSC_COMM_SELF,nrow,perm,PETSC_COPY_VALUES,row);
 32:   ISCreateGeneral(PETSC_COMM_SELF,nrow,perm,PETSC_OWN_POINTER,col);
 33:   return(0);
 34: }