xref: /petsc/src/mat/impls/sbaij/seq/sbaij2.c (revision c40ae8730e1156c97d0dc1f9569c0c972cb9ef2b)

#include <../src/mat/impls/baij/seq/baij.h>
#include <petsc/private/kernels/blockinvert.h>
#include <petscbt.h>
#include <../src/mat/impls/sbaij/seq/sbaij.h>
#include <petscblaslapack.h>

PetscErrorCode MatIncreaseOverlap_SeqSBAIJ(Mat A,PetscInt is_max,IS is[],PetscInt ov)
{
  Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data;
  PetscErrorCode ierr;
  PetscInt       brow,i,j,k,l,mbs,n,*nidx,isz,bcol,bcol_max,start,end,*ai,*aj,bs,*nidx2;
  const PetscInt *idx;
  PetscBT        table_out,table_in;

  PetscFunctionBegin;
  if (ov < 0) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Negative overlap specified");
  mbs  = a->mbs;
  ai   = a->i;
  aj   = a->j;
  bs   = A->rmap->bs;
  ierr = PetscBTCreate(mbs,&table_out);CHKERRQ(ierr);
  ierr = PetscMalloc1(mbs+1,&nidx);CHKERRQ(ierr);
  ierr = PetscMalloc1(A->rmap->N+1,&nidx2);CHKERRQ(ierr);
  ierr = PetscBTCreate(mbs,&table_in);CHKERRQ(ierr);

  for (i=0; i<is_max; i++) { /* for each is */
    isz  = 0;
    ierr = PetscBTMemzero(mbs,table_out);CHKERRQ(ierr);

    /* Extract the indices, assume there can be duplicate entries */
    ierr = ISGetIndices(is[i],&idx);CHKERRQ(ierr);
    ierr = ISGetLocalSize(is[i],&n);CHKERRQ(ierr);

    /* Enter these into the temp arrays i.e mark table_out[brow], enter brow into new index */
    bcol_max = 0;
    for (j=0; j<n; ++j) {
      brow = idx[j]/bs; /* convert the indices into block indices */
      if (brow >= mbs) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"index greater than mat-dim");
      if (!PetscBTLookupSet(table_out,brow)) {
        nidx[isz++] = brow;
        if (bcol_max < brow) bcol_max = brow;
      }
    }
    ierr = ISRestoreIndices(is[i],&idx);CHKERRQ(ierr);
    ierr = ISDestroy(&is[i]);CHKERRQ(ierr);

    k = 0;
    for (j=0; j<ov; j++) { /* for each overlap */
      /* set table_in for lookup - only mark entries that are added onto nidx in (j-1)-th overlap */
      ierr = PetscBTMemzero(mbs,table_in);CHKERRQ(ierr);
      for (l=k; l<isz; l++) { ierr = PetscBTSet(table_in,nidx[l]);CHKERRQ(ierr); }

      n = isz;  /* length of the updated is[i] */
      for (brow=0; brow<mbs; brow++) {
        start = ai[brow]; end   = ai[brow+1];
        if (PetscBTLookup(table_in,brow)) { /* brow is on nidx - row search: collect all bcol in this brow */
          for (l = start; l<end; l++) {
            bcol = aj[l];
            if (!PetscBTLookupSet(table_out,bcol)) {
              nidx[isz++] = bcol;
              if (bcol_max < bcol) bcol_max = bcol;
            }
          }
          k++;
          if (k >= n) break; /* for (brow=0; brow<mbs; brow++) */
        } else { /* brow is not on nidx - col serach: add brow onto nidx if there is a bcol in nidx */
          for (l = start; l<end; l++) {
            bcol = aj[l];
            if (bcol > bcol_max) break;
            if (PetscBTLookup(table_in,bcol)) {
              if (!PetscBTLookupSet(table_out,brow)) nidx[isz++] = brow;
              break; /* for l = start; l<end ; l++) */
            }
          }
        }
      }
    } /* for each overlap */

    /* expand the Index Set */
    for (j=0; j<isz; j++) {
      for (k=0; k<bs; k++) nidx2[j*bs+k] = nidx[j]*bs+k;
    }
    ierr = ISCreateGeneral(PETSC_COMM_SELF,isz*bs,nidx2,PETSC_COPY_VALUES,is+i);CHKERRQ(ierr);
  }
  ierr = PetscBTDestroy(&table_out);CHKERRQ(ierr);
  ierr = PetscFree(nidx);CHKERRQ(ierr);
  ierr = PetscFree(nidx2);CHKERRQ(ierr);
  ierr = PetscBTDestroy(&table_in);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/* Bseq is non-symmetric SBAIJ matrix, only used internally by PETSc.
        Zero some ops' to avoid invalid usse */
PetscErrorCode MatSeqSBAIJZeroOps_Private(Mat Bseq)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = MatSetOption(Bseq,MAT_SYMMETRIC,PETSC_FALSE);CHKERRQ(ierr);
  Bseq->ops->mult                   = 0;
  Bseq->ops->multadd                = 0;
  Bseq->ops->multtranspose          = 0;
  Bseq->ops->multtransposeadd       = 0;
  Bseq->ops->lufactor               = 0;
  Bseq->ops->choleskyfactor         = 0;
  Bseq->ops->lufactorsymbolic       = 0;
  Bseq->ops->choleskyfactorsymbolic = 0;
  Bseq->ops->getinertia             = 0;
  PetscFunctionReturn(0);
}

/* same as MatCreateSubMatrices_SeqBAIJ(), except cast Mat_SeqSBAIJ */
PetscErrorCode MatCreateSubMatrix_SeqSBAIJ_Private(Mat A,IS isrow,IS iscol,MatReuse scall,Mat *B)
{
  Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data,*c;
  PetscErrorCode ierr;
  PetscInt       *smap,i,k,kstart,kend,oldcols = a->nbs,*lens;
  PetscInt       row,mat_i,*mat_j,tcol,*mat_ilen;
  const PetscInt *irow,*icol;
  PetscInt       nrows,ncols,*ssmap,bs=A->rmap->bs,bs2=a->bs2;
  PetscInt       *aj = a->j,*ai = a->i;
  MatScalar      *mat_a;
  Mat            C;
  PetscBool      flag;

  PetscFunctionBegin;

  ierr = ISGetIndices(isrow,&irow);CHKERRQ(ierr);
  ierr = ISGetIndices(iscol,&icol);CHKERRQ(ierr);
  ierr = ISGetLocalSize(isrow,&nrows);CHKERRQ(ierr);
  ierr = ISGetLocalSize(iscol,&ncols);CHKERRQ(ierr);

  ierr  = PetscCalloc1(1+oldcols,&smap);CHKERRQ(ierr);
  ssmap = smap;
  ierr  = PetscMalloc1(1+nrows,&lens);CHKERRQ(ierr);
  for (i=0; i<ncols; i++) smap[icol[i]] = i+1;
  /* determine lens of each row */
  for (i=0; i<nrows; i++) {
    kstart  = ai[irow[i]];
    kend    = kstart + a->ilen[irow[i]];
    lens[i] = 0;
    for (k=kstart; k<kend; k++) {
      if (ssmap[aj[k]]) lens[i]++;
    }
  }
  /* Create and fill new matrix */
  if (scall == MAT_REUSE_MATRIX) {
    c = (Mat_SeqSBAIJ*)((*B)->data);

    if (c->mbs!=nrows || c->nbs!=ncols || (*B)->rmap->bs!=bs) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Submatrix wrong size");
    ierr = PetscArraycmp(c->ilen,lens,c->mbs,&flag);CHKERRQ(ierr);
    if (!flag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Cannot reuse matrix. wrong no of nonzeros");
    ierr = PetscArrayzero(c->ilen,c->mbs);CHKERRQ(ierr);
    C    = *B;
  } else {
    ierr = MatCreate(PetscObjectComm((PetscObject)A),&C);CHKERRQ(ierr);
    ierr = MatSetSizes(C,nrows*bs,ncols*bs,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
    ierr = MatSetType(C,((PetscObject)A)->type_name);CHKERRQ(ierr);
    ierr = MatSeqSBAIJSetPreallocation(C,bs,0,lens);CHKERRQ(ierr);
  }
  c = (Mat_SeqSBAIJ*)(C->data);
  for (i=0; i<nrows; i++) {
    row      = irow[i];
    kstart   = ai[row];
    kend     = kstart + a->ilen[row];
    mat_i    = c->i[i];
    mat_j    = c->j + mat_i;
    mat_a    = c->a + mat_i*bs2;
    mat_ilen = c->ilen + i;
    for (k=kstart; k<kend; k++) {
      if ((tcol=ssmap[a->j[k]])) {
        *mat_j++ = tcol - 1;
        ierr     = PetscArraycpy(mat_a,a->a+k*bs2,bs2);CHKERRQ(ierr);
        mat_a   += bs2;
        (*mat_ilen)++;
      }
    }
  }
  /* sort */
  {
    MatScalar *work;

    ierr = PetscMalloc1(bs2,&work);CHKERRQ(ierr);
    for (i=0; i<nrows; i++) {
      PetscInt ilen;
      mat_i = c->i[i];
      mat_j = c->j + mat_i;
      mat_a = c->a + mat_i*bs2;
      ilen  = c->ilen[i];
      ierr  = PetscSortIntWithDataArray(ilen,mat_j,mat_a,bs2*sizeof(MatScalar),work);CHKERRQ(ierr);
    }
    ierr = PetscFree(work);CHKERRQ(ierr);
  }

  /* Free work space */
  ierr = ISRestoreIndices(iscol,&icol);CHKERRQ(ierr);
  ierr = PetscFree(smap);CHKERRQ(ierr);
  ierr = PetscFree(lens);CHKERRQ(ierr);
  ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  ierr = ISRestoreIndices(isrow,&irow);CHKERRQ(ierr);
  *B   = C;
  PetscFunctionReturn(0);
}

PetscErrorCode MatCreateSubMatrix_SeqSBAIJ(Mat A,IS isrow,IS iscol,MatReuse scall,Mat *B)
{
  Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data;
  IS             is1,is2;
  PetscErrorCode ierr;
  PetscInt       *vary,*iary,nrows,ncols,i,bs=A->rmap->bs,count,maxmnbs;
  const PetscInt *irow,*icol;

  PetscFunctionBegin;
  ierr = ISGetIndices(isrow,&irow);CHKERRQ(ierr);
  ierr = ISGetIndices(iscol,&icol);CHKERRQ(ierr);
  ierr = ISGetLocalSize(isrow,&nrows);CHKERRQ(ierr);
  ierr = ISGetLocalSize(iscol,&ncols);CHKERRQ(ierr);

  /* Verify if the indices corespond to each element in a block
   and form the IS with compressed IS */
  maxmnbs = PetscMax(a->mbs,a->nbs);
  ierr = PetscMalloc2(maxmnbs,&vary,maxmnbs,&iary);CHKERRQ(ierr);
  ierr = PetscArrayzero(vary,a->mbs);CHKERRQ(ierr);
  for (i=0; i<nrows; i++) vary[irow[i]/bs]++;
  for (i=0; i<a->mbs; i++) {
    if (vary[i]!=0 && vary[i]!=bs) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Index set does not match blocks");
  }
  count = 0;
  for (i=0; i<nrows; i++) {
    PetscInt j = irow[i] / bs;
    if ((vary[j]--)==bs) iary[count++] = j;
  }
  ierr = ISCreateGeneral(PETSC_COMM_SELF,count,iary,PETSC_COPY_VALUES,&is1);CHKERRQ(ierr);

  ierr = PetscArrayzero(vary,a->nbs);CHKERRQ(ierr);
  for (i=0; i<ncols; i++) vary[icol[i]/bs]++;
  for (i=0; i<a->nbs; i++) {
    if (vary[i]!=0 && vary[i]!=bs) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Internal error in PETSc");
  }
  count = 0;
  for (i=0; i<ncols; i++) {
    PetscInt j = icol[i] / bs;
    if ((vary[j]--)==bs) iary[count++] = j;
  }
  ierr = ISCreateGeneral(PETSC_COMM_SELF,count,iary,PETSC_COPY_VALUES,&is2);CHKERRQ(ierr);
  ierr = ISRestoreIndices(isrow,&irow);CHKERRQ(ierr);
  ierr = ISRestoreIndices(iscol,&icol);CHKERRQ(ierr);
  ierr = PetscFree2(vary,iary);CHKERRQ(ierr);

  ierr = MatCreateSubMatrix_SeqSBAIJ_Private(A,is1,is2,scall,B);CHKERRQ(ierr);
  ierr = ISDestroy(&is1);CHKERRQ(ierr);
  ierr = ISDestroy(&is2);CHKERRQ(ierr);

  if (isrow != iscol) {
    PetscBool isequal;
    ierr = ISEqual(isrow,iscol,&isequal);CHKERRQ(ierr);
    if (!isequal) {
      ierr = MatSeqSBAIJZeroOps_Private(*B);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

PetscErrorCode MatCreateSubMatrices_SeqSBAIJ(Mat A,PetscInt n,const IS irow[],const IS icol[],MatReuse scall,Mat *B[])
{
  PetscErrorCode ierr;
  PetscInt       i;

  PetscFunctionBegin;
  if (scall == MAT_INITIAL_MATRIX) {
    ierr = PetscCalloc1(n+1,B);CHKERRQ(ierr);
  }

  for (i=0; i<n; i++) {
    ierr = MatCreateSubMatrix_SeqSBAIJ(A,irow[i],icol[i],scall,&(*B)[i]);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

/* -------------------------------------------------------*/
/* Should check that shapes of vectors and matrices match */
/* -------------------------------------------------------*/

PetscErrorCode MatMult_SeqSBAIJ_2(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[2*i]   += v[0]*x1 + v[2]*x2;
      z[2*i+1] += v[2]*x1 + v[3]*x2;
      v        += 4; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+4*n,4*n,0,PETSC_PREFETCH_HINT_NTA);   /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*2;
      z[cval]   += v[0]*x1 + v[1]*x2;
      z[cval+1] += v[2]*x1 + v[3]*x2;
      /* (strict upper triangular part of A)*x  */
      z[2*i]   += v[0]*x[cval] + v[2]*x[cval+1];
      z[2*i+1] += v[1]*x[cval] + v[3]*x[cval+1];
      v        += 4;
    }
    xb +=2; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(8.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMult_SeqSBAIJ_3(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj = a->j,*ai = a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[3*i]   += v[0]*x1 + v[3]*x2 + v[6]*x3;
      z[3*i+1] += v[3]*x1 + v[4]*x2 + v[7]*x3;
      z[3*i+2] += v[6]*x1 + v[7]*x2 + v[8]*x3;
      v        += 9; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+9*n,9*n,0,PETSC_PREFETCH_HINT_NTA);   /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*3;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3;
      z[cval+1] += v[3]*x1 + v[4]*x2 + v[5]*x3;
      z[cval+2] += v[6]*x1 + v[7]*x2 + v[8]*x3;
      /* (strict upper triangular part of A)*x  */
      z[3*i]   += v[0]*x[cval] + v[3]*x[cval+1]+ v[6]*x[cval+2];
      z[3*i+1] += v[1]*x[cval] + v[4]*x[cval+1]+ v[7]*x[cval+2];
      z[3*i+2] += v[2]*x[cval] + v[5]*x[cval+1]+ v[8]*x[cval+2];
      v        += 9;
    }
    xb +=3; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(18.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMult_SeqSBAIJ_4(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj = a->j,*ai = a->i,*ib;
  PetscInt          nonzerorow = 0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[4*i]   += v[0]*x1 + v[4]*x2 +  v[8]*x3 + v[12]*x4;
      z[4*i+1] += v[4]*x1 + v[5]*x2 +  v[9]*x3 + v[13]*x4;
      z[4*i+2] += v[8]*x1 + v[9]*x2 + v[10]*x3 + v[14]*x4;
      z[4*i+3] += v[12]*x1+ v[13]*x2+ v[14]*x3 + v[15]*x4;
      v        += 16; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+16*n,16*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*4;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3 + v[3]*x4;
      z[cval+1] += v[4]*x1 + v[5]*x2 + v[6]*x3 + v[7]*x4;
      z[cval+2] += v[8]*x1 + v[9]*x2 + v[10]*x3 + v[11]*x4;
      z[cval+3] += v[12]*x1 + v[13]*x2 + v[14]*x3 + v[15]*x4;
      /* (strict upper triangular part of A)*x  */
      z[4*i]   += v[0]*x[cval] + v[4]*x[cval+1]+ v[8]*x[cval+2] + v[12]*x[cval+3];
      z[4*i+1] += v[1]*x[cval] + v[5]*x[cval+1]+ v[9]*x[cval+2] + v[13]*x[cval+3];
      z[4*i+2] += v[2]*x[cval] + v[6]*x[cval+1]+ v[10]*x[cval+2]+ v[14]*x[cval+3];
      z[4*i+3] += v[3]*x[cval] + v[7]*x[cval+1]+ v[11]*x[cval+2]+ v[15]*x[cval+3];
      v        += 16;
    }
    xb +=4; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(32.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMult_SeqSBAIJ_5(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj = a->j,*ai = a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[5*i]   += v[0]*x1  + v[5]*x2 + v[10]*x3 + v[15]*x4+ v[20]*x5;
      z[5*i+1] += v[5]*x1  + v[6]*x2 + v[11]*x3 + v[16]*x4+ v[21]*x5;
      z[5*i+2] += v[10]*x1 +v[11]*x2 + v[12]*x3 + v[17]*x4+ v[22]*x5;
      z[5*i+3] += v[15]*x1 +v[16]*x2 + v[17]*x3 + v[18]*x4+ v[23]*x5;
      z[5*i+4] += v[20]*x1 +v[21]*x2 + v[22]*x3 + v[23]*x4+ v[24]*x5;
      v        += 25; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+25*n,25*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*5;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3 + v[3]*x4 + v[4]*x5;
      z[cval+1] += v[5]*x1 + v[6]*x2 + v[7]*x3 + v[8]*x4 + v[9]*x5;
      z[cval+2] += v[10]*x1 + v[11]*x2 + v[12]*x3 + v[13]*x4+ v[14]*x5;
      z[cval+3] += v[15]*x1 + v[16]*x2 + v[17]*x3 + v[18]*x4+ v[19]*x5;
      z[cval+4] += v[20]*x1 + v[21]*x2 + v[22]*x3 + v[23]*x4+ v[24]*x5;
      /* (strict upper triangular part of A)*x  */
      z[5*i]   +=v[0]*x[cval]+v[5]*x[cval+1]+v[10]*x[cval+2]+v[15]*x[cval+3]+v[20]*x[cval+4];
      z[5*i+1] +=v[1]*x[cval]+v[6]*x[cval+1]+v[11]*x[cval+2]+v[16]*x[cval+3]+v[21]*x[cval+4];
      z[5*i+2] +=v[2]*x[cval]+v[7]*x[cval+1]+v[12]*x[cval+2]+v[17]*x[cval+3]+v[22]*x[cval+4];
      z[5*i+3] +=v[3]*x[cval]+v[8]*x[cval+1]+v[13]*x[cval+2]+v[18]*x[cval+3]+v[23]*x[cval+4];
      z[5*i+4] +=v[4]*x[cval]+v[9]*x[cval+1]+v[14]*x[cval+2]+v[19]*x[cval+3]+v[24]*x[cval+4];
      v        += 25;
    }
    xb +=5; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(50.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}


PetscErrorCode MatMult_SeqSBAIJ_6(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5,x6,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4]; x6=xb[5];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[6*i]   += v[0]*x1  + v[6]*x2 + v[12]*x3 + v[18]*x4+ v[24]*x5 + v[30]*x6;
      z[6*i+1] += v[6]*x1  + v[7]*x2 + v[13]*x3 + v[19]*x4+ v[25]*x5 + v[31]*x6;
      z[6*i+2] += v[12]*x1 +v[13]*x2 + v[14]*x3 + v[20]*x4+ v[26]*x5 + v[32]*x6;
      z[6*i+3] += v[18]*x1 +v[19]*x2 + v[20]*x3 + v[21]*x4+ v[27]*x5 + v[33]*x6;
      z[6*i+4] += v[24]*x1 +v[25]*x2 + v[26]*x3 + v[27]*x4+ v[28]*x5 + v[34]*x6;
      z[6*i+5] += v[30]*x1 +v[31]*x2 + v[32]*x3 + v[33]*x4+ v[34]*x5 + v[35]*x6;
      v        += 36; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+36*n,36*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*6;
      z[cval]   += v[0]*x1  + v[1]*x2 + v[2]*x3 + v[3]*x4+ v[4]*x5 + v[5]*x6;
      z[cval+1] += v[6]*x1  + v[7]*x2 + v[8]*x3 + v[9]*x4+ v[10]*x5 + v[11]*x6;
      z[cval+2] += v[12]*x1  + v[13]*x2 + v[14]*x3 + v[15]*x4+ v[16]*x5 + v[17]*x6;
      z[cval+3] += v[18]*x1  + v[19]*x2 + v[20]*x3 + v[21]*x4+ v[22]*x5 + v[23]*x6;
      z[cval+4] += v[24]*x1  + v[25]*x2 + v[26]*x3 + v[27]*x4+ v[28]*x5 + v[29]*x6;
      z[cval+5] += v[30]*x1  + v[31]*x2 + v[32]*x3 + v[33]*x4+ v[34]*x5 + v[35]*x6;
      /* (strict upper triangular part of A)*x  */
      z[6*i]   +=v[0]*x[cval]+v[6]*x[cval+1]+v[12]*x[cval+2]+v[18]*x[cval+3]+v[24]*x[cval+4]+v[30]*x[cval+5];
      z[6*i+1] +=v[1]*x[cval]+v[7]*x[cval+1]+v[13]*x[cval+2]+v[19]*x[cval+3]+v[25]*x[cval+4]+v[31]*x[cval+5];
      z[6*i+2] +=v[2]*x[cval]+v[8]*x[cval+1]+v[14]*x[cval+2]+v[20]*x[cval+3]+v[26]*x[cval+4]+v[32]*x[cval+5];
      z[6*i+3] +=v[3]*x[cval]+v[9]*x[cval+1]+v[15]*x[cval+2]+v[21]*x[cval+3]+v[27]*x[cval+4]+v[33]*x[cval+5];
      z[6*i+4] +=v[4]*x[cval]+v[10]*x[cval+1]+v[16]*x[cval+2]+v[22]*x[cval+3]+v[28]*x[cval+4]+v[34]*x[cval+5];
      z[6*i+5] +=v[5]*x[cval]+v[11]*x[cval+1]+v[17]*x[cval+2]+v[23]*x[cval+3]+v[29]*x[cval+4]+v[35]*x[cval+5];
      v        += 36;
    }
    xb +=6; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(72.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
PetscErrorCode MatMult_SeqSBAIJ_7(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5,x6,x7,zero=0.0;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4]; x6=xb[5]; x7=xb[6];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[7*i]   += v[0]*x1 + v[7]*x2 + v[14]*x3 + v[21]*x4+ v[28]*x5 + v[35]*x6+ v[42]*x7;
      z[7*i+1] += v[7]*x1 + v[8]*x2 + v[15]*x3 + v[22]*x4+ v[29]*x5 + v[36]*x6+ v[43]*x7;
      z[7*i+2] += v[14]*x1+ v[15]*x2 +v[16]*x3 + v[23]*x4+ v[30]*x5 + v[37]*x6+ v[44]*x7;
      z[7*i+3] += v[21]*x1+ v[22]*x2 +v[23]*x3 + v[24]*x4+ v[31]*x5 + v[38]*x6+ v[45]*x7;
      z[7*i+4] += v[28]*x1+ v[29]*x2 +v[30]*x3 + v[31]*x4+ v[32]*x5 + v[39]*x6+ v[46]*x7;
      z[7*i+5] += v[35]*x1+ v[36]*x2 +v[37]*x3 + v[38]*x4+ v[39]*x5 + v[40]*x6+ v[47]*x7;
      z[7*i+6] += v[42]*x1+ v[43]*x2 +v[44]*x3 + v[45]*x4+ v[46]*x5 + v[47]*x6+ v[48]*x7;
      v        += 49; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+49*n,49*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*7;
      z[cval]   += v[0]*x1  + v[1]*x2 + v[2]*x3 + v[3]*x4+ v[4]*x5 + v[5]*x6+ v[6]*x7;
      z[cval+1] += v[7]*x1  + v[8]*x2 + v[9]*x3 + v[10]*x4+ v[11]*x5 + v[12]*x6+ v[13]*x7;
      z[cval+2] += v[14]*x1  + v[15]*x2 + v[16]*x3 + v[17]*x4+ v[18]*x5 + v[19]*x6+ v[20]*x7;
      z[cval+3] += v[21]*x1  + v[22]*x2 + v[23]*x3 + v[24]*x4+ v[25]*x5 + v[26]*x6+ v[27]*x7;
      z[cval+4] += v[28]*x1  + v[29]*x2 + v[30]*x3 + v[31]*x4+ v[32]*x5 + v[33]*x6+ v[34]*x7;
      z[cval+5] += v[35]*x1  + v[36]*x2 + v[37]*x3 + v[38]*x4+ v[39]*x5 + v[40]*x6+ v[41]*x7;
      z[cval+6] += v[42]*x1  + v[43]*x2 + v[44]*x3 + v[45]*x4+ v[46]*x5 + v[47]*x6+ v[48]*x7;
      /* (strict upper triangular part of A)*x  */
      z[7*i]  +=v[0]*x[cval]+v[7]*x[cval+1]+v[14]*x[cval+2]+v[21]*x[cval+3]+v[28]*x[cval+4]+v[35]*x[cval+5]+v[42]*x[cval+6];
      z[7*i+1]+=v[1]*x[cval]+v[8]*x[cval+1]+v[15]*x[cval+2]+v[22]*x[cval+3]+v[29]*x[cval+4]+v[36]*x[cval+5]+v[43]*x[cval+6];
      z[7*i+2]+=v[2]*x[cval]+v[9]*x[cval+1]+v[16]*x[cval+2]+v[23]*x[cval+3]+v[30]*x[cval+4]+v[37]*x[cval+5]+v[44]*x[cval+6];
      z[7*i+3]+=v[3]*x[cval]+v[10]*x[cval+1]+v[17]*x[cval+2]+v[24]*x[cval+3]+v[31]*x[cval+4]+v[38]*x[cval+5]+v[45]*x[cval+6];
      z[7*i+4]+=v[4]*x[cval]+v[11]*x[cval+1]+v[18]*x[cval+2]+v[25]*x[cval+3]+v[32]*x[cval+4]+v[39]*x[cval+5]+v[46]*x[cval+6];
      z[7*i+5]+=v[5]*x[cval]+v[12]*x[cval+1]+v[19]*x[cval+2]+v[26]*x[cval+3]+v[33]*x[cval+4]+v[40]*x[cval+5]+v[47]*x[cval+6];
      z[7*i+6]+=v[6]*x[cval]+v[13]*x[cval+1]+v[20]*x[cval+2]+v[27]*x[cval+3]+v[34]*x[cval+4]+v[41]*x[cval+5]+v[48]*x[cval+6];
      v       += 49;
    }
    xb +=7; ai++;
  }
  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(98.0*(a->nz*2.0 - nonzerorow) - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*
    This will not work with MatScalar == float because it calls the BLAS
*/
PetscErrorCode MatMult_SeqSBAIJ_N(Mat A,Vec xx,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,*z_ptr,*zb,*work,*workt,zero=0.0;
  const PetscScalar *x,*x_ptr,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs =a->mbs,i,bs=A->rmap->bs,j,n,bs2=a->bs2,ncols,k;
  const PetscInt    *idx,*aj,*ii;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecSet(zz,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);x_ptr = x;
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr); z_ptr=z;

  aj = a->j;
  v  = a->a;
  ii = a->i;

  if (!a->mult_work) {
    ierr = PetscMalloc1(A->rmap->N+1,&a->mult_work);CHKERRQ(ierr);
  }
  work = a->mult_work;

  for (i=0; i<mbs; i++) {
    n           = ii[1] - ii[0]; ncols = n*bs;
    workt       = work; idx=aj+ii[0];
    nonzerorow += (n>0);

    /* upper triangular part */
    for (j=0; j<n; j++) {
      xb = x_ptr + bs*(*idx++);
      for (k=0; k<bs; k++) workt[k] = xb[k];
      workt += bs;
    }
    /* z(i*bs:(i+1)*bs-1) += A(i,:)*x */
    PetscKernel_w_gets_w_plus_Ar_times_v(bs,ncols,work,v,z);

    /* strict lower triangular part */
    idx = aj+ii[0];
    if (*idx == i) {
      ncols -= bs; v += bs2; idx++; n--;
    }

    if (ncols > 0) {
      workt = work;
      ierr  = PetscArrayzero(workt,ncols);CHKERRQ(ierr);
      PetscKernel_w_gets_w_plus_trans_Ar_times_v(bs,ncols,x,v,workt);
      for (j=0; j<n; j++) {
        zb = z_ptr + bs*(*idx++);
        for (k=0; k<bs; k++) zb[k] += workt[k];
        workt += bs;
      }
    }
    x += bs; v += n*bs2; z += bs; ii++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);
  ierr = PetscLogFlops(2.0*(a->nz*2.0 - nonzerorow)*bs2 - nonzerorow);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_1(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs =a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);
  v    = a->a;
  xb   = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th row of A */
    x1          = xb[0];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {            /* (diag of A)*x */
      z[i] += *v++ * x[*ib++]; jmin++;
    }
    for (j=jmin; j<n; j++) {
      cval    = *ib;
      z[cval] += *v * x1;      /* (strict lower triangular part of A)*x  */
      z[i] += *v++ * x[*ib++]; /* (strict upper triangular part of A)*x  */
    }
    xb++; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(2.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_2(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs =a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[2*i]   += v[0]*x1 + v[2]*x2;
      z[2*i+1] += v[2]*x1 + v[3]*x2;
      v        += 4; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+4*n,4*n,0,PETSC_PREFETCH_HINT_NTA);   /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*2;
      z[cval]   += v[0]*x1 + v[1]*x2;
      z[cval+1] += v[2]*x1 + v[3]*x2;
      /* (strict upper triangular part of A)*x  */
      z[2*i]   += v[0]*x[cval] + v[2]*x[cval+1];
      z[2*i+1] += v[1]*x[cval] + v[3]*x[cval+1];
      v        += 4;
    }
    xb +=2; ai++;
  }
  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(4.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_3(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[3*i]   += v[0]*x1 + v[3]*x2 + v[6]*x3;
      z[3*i+1] += v[3]*x1 + v[4]*x2 + v[7]*x3;
      z[3*i+2] += v[6]*x1 + v[7]*x2 + v[8]*x3;
      v        += 9; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+9*n,9*n,0,PETSC_PREFETCH_HINT_NTA);   /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*3;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3;
      z[cval+1] += v[3]*x1 + v[4]*x2 + v[5]*x3;
      z[cval+2] += v[6]*x1 + v[7]*x2 + v[8]*x3;
      /* (strict upper triangular part of A)*x  */
      z[3*i]   += v[0]*x[cval] + v[3]*x[cval+1]+ v[6]*x[cval+2];
      z[3*i+1] += v[1]*x[cval] + v[4]*x[cval+1]+ v[7]*x[cval+2];
      z[3*i+2] += v[2]*x[cval] + v[5]*x[cval+1]+ v[8]*x[cval+2];
      v        += 9;
    }
    xb +=3; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(18.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_4(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[4*i]   += v[0]*x1 + v[4]*x2 +  v[8]*x3 + v[12]*x4;
      z[4*i+1] += v[4]*x1 + v[5]*x2 +  v[9]*x3 + v[13]*x4;
      z[4*i+2] += v[8]*x1 + v[9]*x2 + v[10]*x3 + v[14]*x4;
      z[4*i+3] += v[12]*x1+ v[13]*x2+ v[14]*x3 + v[15]*x4;
      v        += 16; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+16*n,16*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*4;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3 + v[3]*x4;
      z[cval+1] += v[4]*x1 + v[5]*x2 + v[6]*x3 + v[7]*x4;
      z[cval+2] += v[8]*x1 + v[9]*x2 + v[10]*x3 + v[11]*x4;
      z[cval+3] += v[12]*x1 + v[13]*x2 + v[14]*x3 + v[15]*x4;
      /* (strict upper triangular part of A)*x  */
      z[4*i]   += v[0]*x[cval] + v[4]*x[cval+1]+ v[8]*x[cval+2] + v[12]*x[cval+3];
      z[4*i+1] += v[1]*x[cval] + v[5]*x[cval+1]+ v[9]*x[cval+2] + v[13]*x[cval+3];
      z[4*i+2] += v[2]*x[cval] + v[6]*x[cval+1]+ v[10]*x[cval+2]+ v[14]*x[cval+3];
      z[4*i+3] += v[3]*x[cval] + v[7]*x[cval+1]+ v[11]*x[cval+2]+ v[15]*x[cval+3];
      v        += 16;
    }
    xb +=4; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(32.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_5(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {      /* (diag of A)*x */
      z[5*i]   += v[0]*x1  + v[5]*x2 + v[10]*x3 + v[15]*x4+ v[20]*x5;
      z[5*i+1] += v[5]*x1  + v[6]*x2 + v[11]*x3 + v[16]*x4+ v[21]*x5;
      z[5*i+2] += v[10]*x1 +v[11]*x2 + v[12]*x3 + v[17]*x4+ v[22]*x5;
      z[5*i+3] += v[15]*x1 +v[16]*x2 + v[17]*x3 + v[18]*x4+ v[23]*x5;
      z[5*i+4] += v[20]*x1 +v[21]*x2 + v[22]*x3 + v[23]*x4+ v[24]*x5;
      v        += 25; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+25*n,25*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*5;
      z[cval]   += v[0]*x1 + v[1]*x2 + v[2]*x3 + v[3]*x4 + v[4]*x5;
      z[cval+1] += v[5]*x1 + v[6]*x2 + v[7]*x3 + v[8]*x4 + v[9]*x5;
      z[cval+2] += v[10]*x1 + v[11]*x2 + v[12]*x3 + v[13]*x4+ v[14]*x5;
      z[cval+3] += v[15]*x1 + v[16]*x2 + v[17]*x3 + v[18]*x4+ v[19]*x5;
      z[cval+4] += v[20]*x1 + v[21]*x2 + v[22]*x3 + v[23]*x4+ v[24]*x5;
      /* (strict upper triangular part of A)*x  */
      z[5*i]   +=v[0]*x[cval]+v[5]*x[cval+1]+v[10]*x[cval+2]+v[15]*x[cval+3]+v[20]*x[cval+4];
      z[5*i+1] +=v[1]*x[cval]+v[6]*x[cval+1]+v[11]*x[cval+2]+v[16]*x[cval+3]+v[21]*x[cval+4];
      z[5*i+2] +=v[2]*x[cval]+v[7]*x[cval+1]+v[12]*x[cval+2]+v[17]*x[cval+3]+v[22]*x[cval+4];
      z[5*i+3] +=v[3]*x[cval]+v[8]*x[cval+1]+v[13]*x[cval+2]+v[18]*x[cval+3]+v[23]*x[cval+4];
      z[5*i+4] +=v[4]*x[cval]+v[9]*x[cval+1]+v[14]*x[cval+2]+v[19]*x[cval+3]+v[24]*x[cval+4];
      v        += 25;
    }
    xb +=5; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(50.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
PetscErrorCode MatMultAdd_SeqSBAIJ_6(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5,x6;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4]; x6=xb[5];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[6*i]   += v[0]*x1  + v[6]*x2 + v[12]*x3 + v[18]*x4+ v[24]*x5 + v[30]*x6;
      z[6*i+1] += v[6]*x1  + v[7]*x2 + v[13]*x3 + v[19]*x4+ v[25]*x5 + v[31]*x6;
      z[6*i+2] += v[12]*x1 +v[13]*x2 + v[14]*x3 + v[20]*x4+ v[26]*x5 + v[32]*x6;
      z[6*i+3] += v[18]*x1 +v[19]*x2 + v[20]*x3 + v[21]*x4+ v[27]*x5 + v[33]*x6;
      z[6*i+4] += v[24]*x1 +v[25]*x2 + v[26]*x3 + v[27]*x4+ v[28]*x5 + v[34]*x6;
      z[6*i+5] += v[30]*x1 +v[31]*x2 + v[32]*x3 + v[33]*x4+ v[34]*x5 + v[35]*x6;
      v        += 36; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+36*n,36*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*6;
      z[cval]   += v[0]*x1  + v[1]*x2 + v[2]*x3 + v[3]*x4+ v[4]*x5 + v[5]*x6;
      z[cval+1] += v[6]*x1  + v[7]*x2 + v[8]*x3 + v[9]*x4+ v[10]*x5 + v[11]*x6;
      z[cval+2] += v[12]*x1  + v[13]*x2 + v[14]*x3 + v[15]*x4+ v[16]*x5 + v[17]*x6;
      z[cval+3] += v[18]*x1  + v[19]*x2 + v[20]*x3 + v[21]*x4+ v[22]*x5 + v[23]*x6;
      z[cval+4] += v[24]*x1  + v[25]*x2 + v[26]*x3 + v[27]*x4+ v[28]*x5 + v[29]*x6;
      z[cval+5] += v[30]*x1  + v[31]*x2 + v[32]*x3 + v[33]*x4+ v[34]*x5 + v[35]*x6;
      /* (strict upper triangular part of A)*x  */
      z[6*i]   +=v[0]*x[cval]+v[6]*x[cval+1]+v[12]*x[cval+2]+v[18]*x[cval+3]+v[24]*x[cval+4]+v[30]*x[cval+5];
      z[6*i+1] +=v[1]*x[cval]+v[7]*x[cval+1]+v[13]*x[cval+2]+v[19]*x[cval+3]+v[25]*x[cval+4]+v[31]*x[cval+5];
      z[6*i+2] +=v[2]*x[cval]+v[8]*x[cval+1]+v[14]*x[cval+2]+v[20]*x[cval+3]+v[26]*x[cval+4]+v[32]*x[cval+5];
      z[6*i+3] +=v[3]*x[cval]+v[9]*x[cval+1]+v[15]*x[cval+2]+v[21]*x[cval+3]+v[27]*x[cval+4]+v[33]*x[cval+5];
      z[6*i+4] +=v[4]*x[cval]+v[10]*x[cval+1]+v[16]*x[cval+2]+v[22]*x[cval+3]+v[28]*x[cval+4]+v[34]*x[cval+5];
      z[6*i+5] +=v[5]*x[cval]+v[11]*x[cval+1]+v[17]*x[cval+2]+v[23]*x[cval+3]+v[29]*x[cval+4]+v[35]*x[cval+5];
      v        += 36;
    }
    xb +=6; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(72.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_7(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,x1,x2,x3,x4,x5,x6,x7;
  const PetscScalar *x,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,n,cval,j,jmin;
  const PetscInt    *aj=a->j,*ai=a->i,*ib;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr);

  v  = a->a;
  xb = x;

  for (i=0; i<mbs; i++) {
    n           = ai[1] - ai[0]; /* length of i_th block row of A */
    x1          = xb[0]; x2 = xb[1]; x3 = xb[2]; x4 = xb[3]; x5=xb[4]; x6=xb[5]; x7=xb[6];
    ib          = aj + *ai;
    jmin        = 0;
    nonzerorow += (n>0);
    if (*ib == i) {     /* (diag of A)*x */
      z[7*i]   += v[0]*x1 + v[7]*x2 + v[14]*x3 + v[21]*x4+ v[28]*x5 + v[35]*x6+ v[42]*x7;
      z[7*i+1] += v[7]*x1 + v[8]*x2 + v[15]*x3 + v[22]*x4+ v[29]*x5 + v[36]*x6+ v[43]*x7;
      z[7*i+2] += v[14]*x1+ v[15]*x2 +v[16]*x3 + v[23]*x4+ v[30]*x5 + v[37]*x6+ v[44]*x7;
      z[7*i+3] += v[21]*x1+ v[22]*x2 +v[23]*x3 + v[24]*x4+ v[31]*x5 + v[38]*x6+ v[45]*x7;
      z[7*i+4] += v[28]*x1+ v[29]*x2 +v[30]*x3 + v[31]*x4+ v[32]*x5 + v[39]*x6+ v[46]*x7;
      z[7*i+5] += v[35]*x1+ v[36]*x2 +v[37]*x3 + v[38]*x4+ v[39]*x5 + v[40]*x6+ v[47]*x7;
      z[7*i+6] += v[42]*x1+ v[43]*x2 +v[44]*x3 + v[45]*x4+ v[46]*x5 + v[47]*x6+ v[48]*x7;
      v        += 49; jmin++;
    }
    PetscPrefetchBlock(ib+jmin+n,n,0,PETSC_PREFETCH_HINT_NTA); /* Indices for the next row (assumes same size as this one) */
    PetscPrefetchBlock(v+49*n,49*n,0,PETSC_PREFETCH_HINT_NTA); /* Entries for the next row */
    for (j=jmin; j<n; j++) {
      /* (strict lower triangular part of A)*x  */
      cval       = ib[j]*7;
      z[cval]   += v[0]*x1  + v[1]*x2 + v[2]*x3 + v[3]*x4+ v[4]*x5 + v[5]*x6+ v[6]*x7;
      z[cval+1] += v[7]*x1  + v[8]*x2 + v[9]*x3 + v[10]*x4+ v[11]*x5 + v[12]*x6+ v[13]*x7;
      z[cval+2] += v[14]*x1  + v[15]*x2 + v[16]*x3 + v[17]*x4+ v[18]*x5 + v[19]*x6+ v[20]*x7;
      z[cval+3] += v[21]*x1  + v[22]*x2 + v[23]*x3 + v[24]*x4+ v[25]*x5 + v[26]*x6+ v[27]*x7;
      z[cval+4] += v[28]*x1  + v[29]*x2 + v[30]*x3 + v[31]*x4+ v[32]*x5 + v[33]*x6+ v[34]*x7;
      z[cval+5] += v[35]*x1  + v[36]*x2 + v[37]*x3 + v[38]*x4+ v[39]*x5 + v[40]*x6+ v[41]*x7;
      z[cval+6] += v[42]*x1  + v[43]*x2 + v[44]*x3 + v[45]*x4+ v[46]*x5 + v[47]*x6+ v[48]*x7;
      /* (strict upper triangular part of A)*x  */
      z[7*i]  +=v[0]*x[cval]+v[7]*x[cval+1]+v[14]*x[cval+2]+v[21]*x[cval+3]+v[28]*x[cval+4]+v[35]*x[cval+5]+v[42]*x[cval+6];
      z[7*i+1]+=v[1]*x[cval]+v[8]*x[cval+1]+v[15]*x[cval+2]+v[22]*x[cval+3]+v[29]*x[cval+4]+v[36]*x[cval+5]+v[43]*x[cval+6];
      z[7*i+2]+=v[2]*x[cval]+v[9]*x[cval+1]+v[16]*x[cval+2]+v[23]*x[cval+3]+v[30]*x[cval+4]+v[37]*x[cval+5]+v[44]*x[cval+6];
      z[7*i+3]+=v[3]*x[cval]+v[10]*x[cval+1]+v[17]*x[cval+2]+v[24]*x[cval+3]+v[31]*x[cval+4]+v[38]*x[cval+5]+v[45]*x[cval+6];
      z[7*i+4]+=v[4]*x[cval]+v[11]*x[cval+1]+v[18]*x[cval+2]+v[25]*x[cval+3]+v[32]*x[cval+4]+v[39]*x[cval+5]+v[46]*x[cval+6];
      z[7*i+5]+=v[5]*x[cval]+v[12]*x[cval+1]+v[19]*x[cval+2]+v[26]*x[cval+3]+v[33]*x[cval+4]+v[40]*x[cval+5]+v[47]*x[cval+6];
      z[7*i+6]+=v[6]*x[cval]+v[13]*x[cval+1]+v[20]*x[cval+2]+v[27]*x[cval+3]+v[34]*x[cval+4]+v[41]*x[cval+5]+v[48]*x[cval+6];
      v       += 49;
    }
    xb +=7; ai++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(98.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatMultAdd_SeqSBAIJ_N(Mat A,Vec xx,Vec yy,Vec zz)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       *z,*z_ptr=0,*zb,*work,*workt;
  const PetscScalar *x,*x_ptr,*xb;
  const MatScalar   *v;
  PetscErrorCode    ierr;
  PetscInt          mbs = a->mbs,i,bs=A->rmap->bs,j,n,bs2=a->bs2,ncols,k;
  const PetscInt    *idx,*aj,*ii;
  PetscInt          nonzerorow=0;

  PetscFunctionBegin;
  ierr = VecCopy(yy,zz);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArrayRead(xx,&x);CHKERRQ(ierr); x_ptr=x;
  ierr = VecGetArray(zz,&z);CHKERRQ(ierr); z_ptr=z;

  aj = a->j;
  v  = a->a;
  ii = a->i;

  if (!a->mult_work) {
    ierr = PetscMalloc1(A->rmap->n+1,&a->mult_work);CHKERRQ(ierr);
  }
  work = a->mult_work;


  for (i=0; i<mbs; i++) {
    n           = ii[1] - ii[0]; ncols = n*bs;
    workt       = work; idx=aj+ii[0];
    nonzerorow += (n>0);

    /* upper triangular part */
    for (j=0; j<n; j++) {
      xb = x_ptr + bs*(*idx++);
      for (k=0; k<bs; k++) workt[k] = xb[k];
      workt += bs;
    }
    /* z(i*bs:(i+1)*bs-1) += A(i,:)*x */
    PetscKernel_w_gets_w_plus_Ar_times_v(bs,ncols,work,v,z);

    /* strict lower triangular part */
    idx = aj+ii[0];
    if (*idx == i) {
      ncols -= bs; v += bs2; idx++; n--;
    }
    if (ncols > 0) {
      workt = work;
      ierr  = PetscArrayzero(workt,ncols);CHKERRQ(ierr);
      PetscKernel_w_gets_w_plus_trans_Ar_times_v(bs,ncols,x,v,workt);
      for (j=0; j<n; j++) {
        zb = z_ptr + bs*(*idx++);
        for (k=0; k<bs; k++) zb[k] += workt[k];
        workt += bs;
      }
    }

    x += bs; v += n*bs2; z += bs; ii++;
  }

  ierr = VecRestoreArrayRead(xx,&x);CHKERRQ(ierr);
  ierr = VecRestoreArray(zz,&z);CHKERRQ(ierr);

  ierr = PetscLogFlops(2.0*(a->nz*2.0 - nonzerorow));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatScale_SeqSBAIJ(Mat inA,PetscScalar alpha)
{
  Mat_SeqSBAIJ   *a     = (Mat_SeqSBAIJ*)inA->data;
  PetscScalar    oalpha = alpha;
  PetscErrorCode ierr;
  PetscBLASInt   one = 1,totalnz;

  PetscFunctionBegin;
  ierr = PetscBLASIntCast(a->bs2*a->nz,&totalnz);CHKERRQ(ierr);
  PetscStackCallBLAS("BLASscal",BLASscal_(&totalnz,&oalpha,a->a,&one));
  ierr = PetscLogFlops(totalnz);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatNorm_SeqSBAIJ(Mat A,NormType type,PetscReal *norm)
{
  Mat_SeqSBAIJ    *a       = (Mat_SeqSBAIJ*)A->data;
  const MatScalar *v       = a->a;
  PetscReal       sum_diag = 0.0, sum_off = 0.0, *sum;
  PetscInt        i,j,k,bs = A->rmap->bs,bs2=a->bs2,k1,mbs=a->mbs,jmin,jmax,nexti,ik,*jl,*il;
  PetscErrorCode  ierr;
  const PetscInt  *aj=a->j,*col;

  PetscFunctionBegin;
  if (!a->nz) {
    *norm = 0.0;
    PetscFunctionReturn(0);
  }
  if (type == NORM_FROBENIUS) {
    for (k=0; k<mbs; k++) {
      jmin = a->i[k]; jmax = a->i[k+1];
      col  = aj + jmin;
      if (*col == k) {         /* diagonal block */
        for (i=0; i<bs2; i++) {
          sum_diag += PetscRealPart(PetscConj(*v)*(*v)); v++;
        }
        jmin++;
      }
      for (j=jmin; j<jmax; j++) {  /* off-diagonal blocks */
        for (i=0; i<bs2; i++) {
          sum_off += PetscRealPart(PetscConj(*v)*(*v)); v++;
        }
      }
    }
    *norm = PetscSqrtReal(sum_diag + 2*sum_off);
    ierr = PetscLogFlops(2*bs2*a->nz);CHKERRQ(ierr);
  } else if (type == NORM_INFINITY || type == NORM_1) {  /* maximum row/column sum */
    ierr = PetscMalloc3(bs,&sum,mbs,&il,mbs,&jl);CHKERRQ(ierr);
    for (i=0; i<mbs; i++) jl[i] = mbs;
    il[0] = 0;

    *norm = 0.0;
    for (k=0; k<mbs; k++) { /* k_th block row */
      for (j=0; j<bs; j++) sum[j]=0.0;
      /*-- col sum --*/
      i = jl[k]; /* first |A(i,k)| to be added */
      /* jl[k]=i: first nozero element in row i for submatrix A(1:k,k:n) (active window)
                  at step k */
      while (i<mbs) {
        nexti = jl[i];  /* next block row to be added */
        ik    = il[i];  /* block index of A(i,k) in the array a */
        for (j=0; j<bs; j++) {
          v = a->a + ik*bs2 + j*bs;
          for (k1=0; k1<bs; k1++) {
            sum[j] += PetscAbsScalar(*v); v++;
          }
        }
        /* update il, jl */
        jmin = ik + 1; /* block index of array a: points to the next nonzero of A in row i */
        jmax = a->i[i+1];
        if (jmin < jmax) {
          il[i] = jmin;
          j     = a->j[jmin];
          jl[i] = jl[j]; jl[j]=i;
        }
        i = nexti;
      }
      /*-- row sum --*/
      jmin = a->i[k]; jmax = a->i[k+1];
      for (i=jmin; i<jmax; i++) {
        for (j=0; j<bs; j++) {
          v = a->a + i*bs2 + j;
          for (k1=0; k1<bs; k1++) {
            sum[j] += PetscAbsScalar(*v); v += bs;
          }
        }
      }
      /* add k_th block row to il, jl */
      col = aj+jmin;
      if (*col == k) jmin++;
      if (jmin < jmax) {
        il[k] = jmin;
        j = a->j[jmin]; jl[k] = jl[j]; jl[j] = k;
      }
      for (j=0; j<bs; j++) {
        if (sum[j] > *norm) *norm = sum[j];
      }
    }
    ierr = PetscFree3(sum,il,jl);CHKERRQ(ierr);
    ierr = PetscLogFlops(PetscMax(mbs*a->nz-1,0));CHKERRQ(ierr);
  } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"No support for this norm yet");
  PetscFunctionReturn(0);
}

PetscErrorCode MatEqual_SeqSBAIJ(Mat A,Mat B,PetscBool * flg)
{
  Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data,*b = (Mat_SeqSBAIJ*)B->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  /* If the  matrix/block dimensions are not equal, or no of nonzeros or shift */
  if ((A->rmap->N != B->rmap->N) || (A->cmap->n != B->cmap->n) || (A->rmap->bs != B->rmap->bs)|| (a->nz != b->nz)) {
    *flg = PETSC_FALSE;
    PetscFunctionReturn(0);
  }

  /* if the a->i are the same */
  ierr = PetscArraycmp(a->i,b->i,a->mbs+1,flg);CHKERRQ(ierr);
  if (!*flg) PetscFunctionReturn(0);

  /* if a->j are the same */
  ierr = PetscArraycmp(a->j,b->j,a->nz,flg);CHKERRQ(ierr);
  if (!*flg) PetscFunctionReturn(0);

  /* if a->a are the same */
  ierr = PetscArraycmp(a->a,b->a,(a->nz)*(A->rmap->bs)*(A->rmap->bs),flg);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatGetDiagonal_SeqSBAIJ(Mat A,Vec v)
{
  Mat_SeqSBAIJ    *a = (Mat_SeqSBAIJ*)A->data;
  PetscErrorCode  ierr;
  PetscInt        i,j,k,row,bs,ambs,bs2;
  const PetscInt  *ai,*aj;
  PetscScalar     *x,zero = 0.0;
  const MatScalar *aa,*aa_j;

  PetscFunctionBegin;
  bs = A->rmap->bs;
  if (A->factortype && bs>1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Not for factored matrix with bs>1");

  aa   = a->a;
  ambs = a->mbs;

  if (A->factortype == MAT_FACTOR_CHOLESKY || A->factortype == MAT_FACTOR_ICC) {
    PetscInt *diag=a->diag;
    aa   = a->a;
    ambs = a->mbs;
    ierr = VecGetArray(v,&x);CHKERRQ(ierr);
    for (i=0; i<ambs; i++) x[i] = 1.0/aa[diag[i]];
    ierr = VecRestoreArray(v,&x);CHKERRQ(ierr);
    PetscFunctionReturn(0);
  }

  ai   = a->i;
  aj   = a->j;
  bs2  = a->bs2;
  ierr = VecSet(v,zero);CHKERRQ(ierr);
  if (!a->nz) PetscFunctionReturn(0);
  ierr = VecGetArray(v,&x);CHKERRQ(ierr);
  for (i=0; i<ambs; i++) {
    j=ai[i];
    if (aj[j] == i) {    /* if this is a diagonal element */
      row  = i*bs;
      aa_j = aa + j*bs2;
      for (k=0; k<bs2; k+=(bs+1),row++) x[row] = aa_j[k];
    }
  }
  ierr = VecRestoreArray(v,&x);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatDiagonalScale_SeqSBAIJ(Mat A,Vec ll,Vec rr)
{
  Mat_SeqSBAIJ      *a = (Mat_SeqSBAIJ*)A->data;
  PetscScalar       x;
  const PetscScalar *l,*li,*ri;
  MatScalar         *aa,*v;
  PetscErrorCode    ierr;
  PetscInt          i,j,k,lm,M,m,mbs,tmp,bs,bs2;
  const PetscInt    *ai,*aj;
  PetscBool         flg;

  PetscFunctionBegin;
  if (ll != rr) {
    ierr = VecEqual(ll,rr,&flg);CHKERRQ(ierr);
    if (!flg) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"For symmetric format, left and right scaling vectors must be same\n");
  }
  if (!ll) PetscFunctionReturn(0);
  ai  = a->i;
  aj  = a->j;
  aa  = a->a;
  m   = A->rmap->N;
  bs  = A->rmap->bs;
  mbs = a->mbs;
  bs2 = a->bs2;

  ierr = VecGetArrayRead(ll,&l);CHKERRQ(ierr);
  ierr = VecGetLocalSize(ll,&lm);CHKERRQ(ierr);
  if (lm != m) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Left scaling vector wrong length");
  for (i=0; i<mbs; i++) { /* for each block row */
    M  = ai[i+1] - ai[i];
    li = l + i*bs;
    v  = aa + bs2*ai[i];
    for (j=0; j<M; j++) { /* for each block */
      ri = l + bs*aj[ai[i]+j];
      for (k=0; k<bs; k++) {
        x = ri[k];
        for (tmp=0; tmp<bs; tmp++) (*v++) *= li[tmp]*x;
      }
    }
  }
  ierr = VecRestoreArrayRead(ll,&l);CHKERRQ(ierr);
  ierr = PetscLogFlops(2.0*a->nz);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

PetscErrorCode MatGetInfo_SeqSBAIJ(Mat A,MatInfoType flag,MatInfo *info)
{
  Mat_SeqSBAIJ *a = (Mat_SeqSBAIJ*)A->data;

  PetscFunctionBegin;
  info->block_size   = a->bs2;
  info->nz_allocated = a->bs2*a->maxnz;   /*num. of nonzeros in upper triangular part */
  info->nz_used      = a->bs2*a->nz;   /*num. of nonzeros in upper triangular part */
  info->nz_unneeded  = (double)(info->nz_allocated - info->nz_used);
  info->assemblies   = A->num_ass;
  info->mallocs      = A->info.mallocs;
  info->memory       = ((PetscObject)A)->mem;
  if (A->factortype) {
    info->fill_ratio_given  = A->info.fill_ratio_given;
    info->fill_ratio_needed = A->info.fill_ratio_needed;
    info->factor_mallocs    = A->info.factor_mallocs;
  } else {
    info->fill_ratio_given  = 0;
    info->fill_ratio_needed = 0;
    info->factor_mallocs    = 0;
  }
  PetscFunctionReturn(0);
}


PetscErrorCode MatZeroEntries_SeqSBAIJ(Mat A)
{
  Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscArrayzero(a->a,a->bs2*a->i[a->mbs]);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*
   This code does not work since it only checks the upper triangular part of
  the matrix. Hence it is not listed in the function table.
*/
PetscErrorCode MatGetRowMaxAbs_SeqSBAIJ(Mat A,Vec v,PetscInt idx[])
{
  Mat_SeqSBAIJ    *a = (Mat_SeqSBAIJ*)A->data;
  PetscErrorCode  ierr;
  PetscInt        i,j,n,row,col,bs,mbs;
  const PetscInt  *ai,*aj;
  PetscReal       atmp;
  const MatScalar *aa;
  PetscScalar     *x;
  PetscInt        ncols,brow,bcol,krow,kcol;

  PetscFunctionBegin;
  if (idx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Send email to petsc-maint@mcs.anl.gov");
  if (A->factortype) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Not for factored matrix");
  bs  = A->rmap->bs;
  aa  = a->a;
  ai  = a->i;
  aj  = a->j;
  mbs = a->mbs;

  ierr = VecSet(v,0.0);CHKERRQ(ierr);
  ierr = VecGetArray(v,&x);CHKERRQ(ierr);
  ierr = VecGetLocalSize(v,&n);CHKERRQ(ierr);
  if (n != A->rmap->N) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Nonconforming matrix and vector");
  for (i=0; i<mbs; i++) {
    ncols = ai[1] - ai[0]; ai++;
    brow  = bs*i;
    for (j=0; j<ncols; j++) {
      bcol = bs*(*aj);
      for (kcol=0; kcol<bs; kcol++) {
        col = bcol + kcol;      /* col index */
        for (krow=0; krow<bs; krow++) {
          atmp = PetscAbsScalar(*aa); aa++;
          row  = brow + krow;   /* row index */
          if (PetscRealPart(x[row]) < atmp) x[row] = atmp;
          if (*aj > i && PetscRealPart(x[col]) < atmp) x[col] = atmp;
        }
      }
      aj++;
    }
  }
  ierr = VecRestoreArray(v,&x);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}