xref: /petsc/src/mat/impls/aij/seq/fdaij.c (revision 2205254efee3a00a594e5e2a3a70f74dcb40bc03)

#include <../src/mat/impls/aij/seq/aij.h>

#undef __FUNCT__
#define __FUNCT__ "MatFDColoringCreate_SeqAIJ"
/*
    This routine is shared by AIJ and BAIJ matrices, since it operators only on the nonzero structure of the elements or blocks.
    This is why it has the ugly code with the MatGetBlockSize()
*/
PetscErrorCode MatFDColoringCreate_SeqAIJ(Mat mat,ISColoring iscoloring,MatFDColoring c)
{
  PetscErrorCode ierr;
  PetscInt       i,n,nrows,N,j,k,m,ncols,col;
  const PetscInt *is,*rows,*ci,*cj;
  PetscInt       nis = iscoloring->n,*rowhit,*columnsforrow,l,bs = 1;
  IS             *isa;
  PetscBool      done,flg = PETSC_FALSE;
  PetscBool      flg1,flg2;

  PetscFunctionBegin;
  if (!mat->assembled) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Matrix must be assembled by calls to MatAssemblyBegin/End();");

  ierr = ISColoringGetIS(iscoloring,PETSC_IGNORE,&isa);CHKERRQ(ierr);
  /* this is ugly way to get blocksize but cannot call MatGetBlockSize() because AIJ can have bs > 1 */
  ierr = PetscObjectTypeCompare((PetscObject)mat,MATSEQBAIJ,&flg1);CHKERRQ(ierr);
  ierr = PetscObjectTypeCompare((PetscObject)mat,MATMPIBAIJ,&flg2);CHKERRQ(ierr);
  if (flg1 || flg2) {
    ierr = MatGetBlockSize(mat,&bs);CHKERRQ(ierr);
  }

  N         = mat->cmap->N/bs;
  c->M      = mat->rmap->N/bs;   /* set total rows, columns and local rows */
  c->N      = mat->cmap->N/bs;
  c->m      = mat->rmap->N/bs;
  c->rstart = 0;

  c->ncolors = nis;
  ierr       = PetscMalloc(nis*sizeof(PetscInt),&c->ncolumns);CHKERRQ(ierr);
  ierr       = PetscMalloc(nis*sizeof(PetscInt*),&c->columns);CHKERRQ(ierr);
  ierr       = PetscMalloc(nis*sizeof(PetscInt),&c->nrows);CHKERRQ(ierr);
  ierr       = PetscMalloc(nis*sizeof(PetscInt*),&c->rows);CHKERRQ(ierr);
  ierr       = PetscMalloc(nis*sizeof(PetscInt*),&c->columnsforrow);CHKERRQ(ierr);

  ierr = MatGetColumnIJ(mat,0,PETSC_FALSE,PETSC_FALSE,&ncols,&ci,&cj,&done);CHKERRQ(ierr);
  if (!done) SETERRQ1(((PetscObject)mat)->comm,PETSC_ERR_SUP,"MatGetColumnIJ() not supported for matrix type %s",((PetscObject)mat)->type_name);

  /*
     Temporary option to allow for debugging/testing
  */
  ierr = PetscOptionsGetBool(PETSC_NULL,"-matfdcoloring_slow",&flg,PETSC_NULL);CHKERRQ(ierr);

  ierr = PetscMalloc((N+1)*sizeof(PetscInt),&rowhit);CHKERRQ(ierr);
  ierr = PetscMalloc((N+1)*sizeof(PetscInt),&columnsforrow);CHKERRQ(ierr);

  for (i=0; i<nis; i++) {
    ierr = ISGetLocalSize(isa[i],&n);CHKERRQ(ierr);
    ierr = ISGetIndices(isa[i],&is);CHKERRQ(ierr);

    c->ncolumns[i] = n;
    if (n) {
      ierr = PetscMalloc(n*sizeof(PetscInt),&c->columns[i]);CHKERRQ(ierr);
      ierr = PetscMemcpy(c->columns[i],is,n*sizeof(PetscInt));CHKERRQ(ierr);
    } else {
      c->columns[i] = 0;
    }

    if (!flg) { /* ------------------------------------------------------------------------------*/
      /* fast, crude version requires O(N*N) work */
      ierr = PetscMemzero(rowhit,N*sizeof(PetscInt));CHKERRQ(ierr);
      /* loop over columns*/
      for (j=0; j<n; j++) {
        col  = is[j];
        rows = cj + ci[col];
        m    = ci[col+1] - ci[col];
        /* loop over columns marking them in rowhit */
        for (k=0; k<m; k++) {
          rowhit[*rows++] = col + 1;
        }
      }
      /* count the number of hits */
      nrows = 0;
      for (j=0; j<N; j++) {
        if (rowhit[j]) nrows++;
      }
      c->nrows[i] = nrows;
      ierr        = PetscMalloc((nrows+1)*sizeof(PetscInt),&c->rows[i]);CHKERRQ(ierr);
      ierr        = PetscMalloc((nrows+1)*sizeof(PetscInt),&c->columnsforrow[i]);CHKERRQ(ierr);
      nrows       = 0;
      for (j=0; j<N; j++) {
        if (rowhit[j]) {
          c->rows[i][nrows]          = j;
          c->columnsforrow[i][nrows] = rowhit[j] - 1;
          nrows++;
        }
      }
    } else {  /*-------------------------------------------------------------------------------*/
      /* slow version, using rowhit as a linked list */
      PetscInt currentcol,fm,mfm;
      rowhit[N] = N;
      nrows     = 0;
      /* loop over columns */
      for (j=0; j<n; j++) {
        col  = is[j];
        rows = cj + ci[col];
        m    = ci[col+1] - ci[col];
        /* loop over columns marking them in rowhit */
        fm = N;    /* fm points to first entry in linked list */
        for (k=0; k<m; k++) {
          currentcol = *rows++;
          /* is it already in the list? */
          do {
            mfm = fm;
            fm  = rowhit[fm];
          } while (fm < currentcol);
          /* not in list so add it */
          if (fm != currentcol) {
            nrows++;
            columnsforrow[currentcol] = col;
            /* next three lines insert new entry into linked list */
            rowhit[mfm]        = currentcol;
            rowhit[currentcol] = fm;
            fm                 = currentcol;
            /* fm points to present position in list since we know the columns are sorted */
          } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Detected invalid coloring");
        }
      }
      c->nrows[i] = nrows;
      ierr        = PetscMalloc((nrows+1)*sizeof(PetscInt),&c->rows[i]);CHKERRQ(ierr);
      ierr        = PetscMalloc((nrows+1)*sizeof(PetscInt),&c->columnsforrow[i]);CHKERRQ(ierr);
      /* now store the linked list of rows into c->rows[i] */
      nrows = 0;
      fm    = rowhit[N];
      do {
        c->rows[i][nrows]            = fm;
        c->columnsforrow[i][nrows++] = columnsforrow[fm];
        fm                           = rowhit[fm];
      } while (fm < N);
    } /* ---------------------------------------------------------------------------------------*/
    ierr = ISRestoreIndices(isa[i],&is);CHKERRQ(ierr);
  }
  ierr = MatRestoreColumnIJ(mat,0,PETSC_FALSE,PETSC_FALSE,&ncols,&ci,&cj,&done);CHKERRQ(ierr);

  ierr = PetscFree(rowhit);CHKERRQ(ierr);
  ierr = PetscFree(columnsforrow);CHKERRQ(ierr);

  /* Optimize by adding the vscale, and scaleforrow[][] fields */
  /*
       see the version for MPIAIJ
  */
  ierr = VecCreateGhost(((PetscObject)mat)->comm,mat->rmap->n,PETSC_DETERMINE,0,PETSC_NULL,&c->vscale);CHKERRQ(ierr);
  ierr = PetscMalloc(c->ncolors*sizeof(PetscInt*),&c->vscaleforrow);CHKERRQ(ierr);
  for (k=0; k<c->ncolors; k++) {
    ierr = PetscMalloc((c->nrows[k]+1)*sizeof(PetscInt),&c->vscaleforrow[k]);CHKERRQ(ierr);
    for (l=0; l<c->nrows[k]; l++) {
      col = c->columnsforrow[k][l];

      c->vscaleforrow[k][l] = col;
    }
  }
  ierr = ISColoringRestoreIS(iscoloring,&isa);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}