convolve()

void convolve	(	const PolyRing *	R,
		const VECTOR(ring_elem) &	input_relems,
		VECTOR(ring_elem) &	output_relems,
		int	convolve_type )

Definition at line 726 of file ringelement.cpp.

{
  const Ring *K = R->getCoefficientRing();
  ring_elem invn;
  size_t n =
      input_relems.size() - 1;  // array is 0..n, with the 0 part being ignored.
  // first set [1, e1] := [1, h1].
  output_relems[0] = input_relems[0];
  for (int i = 1; i <= n; i++)
    {
      // ASSUMPTION: input_relems[i] is either a variable or - of a variable
      ring_elem result = R->copy(input_relems[i]);
      if (convolve_type == 2) R->mult_coeff_to(K->from_long(-i), result);
      for (int j = i - 1; j >= 1; --j)
        {
          ring_elem hr;
          Nterm *g = input_relems[j];
          if (g != nullptr)
            {
              hr.poly_val =
                  R->mult_by_term(output_relems[i - j], g->coeff, g->monom);
              R->internal_add_to(result, hr);
            }
        }
      if (convolve_type == 1)
        {
          invn = K->invert(K->from_long(i));
          R->mult_coeff_to(invn, result);
        }
      output_relems[i] = result;
    }
}

References Nterm::coeff, PolyRing::copy(), Ring::from_long(), PolynomialRing::getCoefficientRing(), PolyRing::internal_add_to(), Ring::invert(), Nterm::monom, PolyRing::mult_by_term(), PolyRing::mult_coeff_to(), ring_elem::poly_val, and result().

Referenced by rawConvolve().