Function gamma

src/compute-engine/numerics/special-functions.ts:46–57

(z: number)

const GAMMA_OVERFLOW_THRESHOLD = 171.6243769563027;

function gammaLanczos(z: number): number {
  z -= 1;
  let x = lanczos_7_c[0];
  for (let i = 1; i < gammaG + 2; i++) x += lanczos_7_c[i] / (z + i);

  const t = z + gammaG + 0.5;
  return Math.sqrt(2 * Math.PI) * Math.pow(t, z + 0.5) * Math.exp(-t) * x;
}

function gammaBalancedProduct(start: number, count: number): number {
  if (count <= 0) return 1;
  if (count === 1) return start;

  const leftCount = count >>> 1;