do_pivots()

void FF_LUComputation::do_pivots ( int lo, int hi, int pivot_col )

private

Definition at line 54 of file fractionfreeLU.cpp.

{
  // Here we clear out row r in columns lo..hi, using the pivot.
  R->remove(lastpivot);
  lastpivot = pivot;
  size_t pivot_row = M->lead_row(
      pivotCol, pivot);  // pivot is the element at (pivot_row, pivotCol)
 
  for (int i = lo; i <= hi; i++)
    {
      ring_elem a;
      size_t r = M->lead_row(i, a);
      if (r == pivot_row)
        {
          // Need to modify column i:
          // col(i) := pivot*M[i] - M[pivot_row,i] * M[pivotCol]
          R->negate_to(a);
          M->scale_column(i, pivot);
          M->column_op(i, a, pivotCol);
        }
 
      if (need_div[i]) M->divide_column(i, lastpivot);
 
      need_div[i] = (r == pivot_row);
    }
}

References lastpivot, M, need_div, pivot, and R.

Referenced by calc().