ratevl Class — pytorch Architecture

Source Code

aten/src/ATen/native/Math.h lines 521–573

template <typename scalar_t>
scalar_t ratevl(scalar_t x, const scalar_t num[], int64_t M,
    const scalar_t denom[], int64_t N) {
  // evaluating rational function, i.e., the ratio of two polynomials
  // the coefficients for numerator are given by `num` while coeffs for
  // denumerator are given by `denom`

  int64_t i, dir;
  scalar_t y, num_ans, denom_ans;
  scalar_t absx = std::fabs(x);
  const scalar_t *p;

  if (absx > 1) {
    /* Evaluate as a polynomial in 1/x. */
    dir = -1;
    p = num + M;
    y = 1 / x;
  }
  else {
    dir = 1;
    p = num;
    y = x;
  }

  /* Evaluate the numerator */
  num_ans = *p;
  p += dir;
  for (i = 1; i <= M; i++) {
    num_ans = num_ans * y + *p;
    p += dir;
  }
  /* Evaluate the denominator */
  if (absx > 1) {
    p = denom + N;
  }
  else {
    p = denom;
  }

  denom_ans = *p;
  p += dir;
  for (i = 1; i <= N; i++) {
    denom_ans = denom_ans * y + *p;
    p += dir;
  }
  if (absx > 1) {
    i = N - M;
    return std::pow(x, i) * num_ans / denom_ans;
  }
  else {
    return num_ans / denom_ans;
  }
}