scan_intervals()

Int scan_intervals	(	char	type,
		Int	ja,
		Int	jb,
		Int	n,
		MDESC *	ma,
		MDESC *	mb,
		Int	q0,
		Int	q1,
		Int	col0,
		Int	col1,
		IDESC *	result
	)

Definition at line 243 of file pctrmr2.c.

{
  Int   offset, j0, j1, templatewidth0, templatewidth1, nbcol0, nbcol1;
  Int   l;      /* local indice on the beginning of the interval */
  assert(type == 'c' || type == 'r');
  nbcol0 = (type == 'c' ? ma->nbcol : ma->nbrow);
  nbcol1 = (type == 'c' ? mb->nbcol : mb->nbrow);
  templatewidth0 = q0 * nbcol0;
  templatewidth1 = q1 * nbcol1;
  {
    Int   sp0 = (type == 'c' ? ma->spcol : ma->sprow);
    Int   sp1 = (type == 'c' ? mb->spcol : mb->sprow);
    j0 = SHIFT(col0, sp0, q0) * nbcol0 - ja;
    j1 = SHIFT(col1, sp1, q1) * nbcol1 - jb;
  }
  offset = 0;
  l = 0;
  /* a small check to verify that the submatrix begin inside the first block
   * of the original matrix, this done by a sort of coordinate change at the
   * beginning of the Cpctrmr2d */
  assert(j0 + nbcol0 > 0);
  assert(j1 + nbcol1 > 0);
  while ((j0 < n) && (j1 < n)) {
    Int   end0, end1;
    Int   start, end;
    end0 = j0 + nbcol0;
    end1 = j1 + nbcol1;
    if (end0 <= j1) {
      j0 += templatewidth0;
      l += nbcol0;
      continue;
    }
    if (end1 <= j0) {
      j1 += templatewidth1;
      continue;
    }
    /* compute the raw intersection */
    start = max(j0, j1);
    start = max(start, 0);
    /* the start is correct now, update the corresponding fields */
    result[offset].gstart = start;
    end = min(end0, end1);
    if (end0 == end) {
      j0 += templatewidth0;
      l += nbcol0;
    }
    if (end1 == end)
      j1 += templatewidth1;
    /* throw the limit if they go out of the matrix */
    end = min(end, n);
    assert(end > start);
    /* it is a bit tricky to see why the length is always positive after all
     * this min and max, first we have the property that every interval
     * considered is at least partly into the submatrix, second we arrive
     * here only if the raw intersection is non-void, if we remove a limit
     * that means the corresponding frontier is in both intervals which
     * proove the final interval is non-void, clear ?? */
    result[offset].len = end - start;
    offset += 1;
  }     /* while */
  return offset;
}