How to deterministically initalize a PRNG from (x, y) coordinates.

GridCoordHashSeed.java

/* How to deterministically initalize a PRNG from (x, y) coordinates. The
 * exact algorithm choice is arbitrary. `coordToLong` could be even simpler.
 * The "hash" is a good scrambling function from 64-bit input to 64-bit
 * output. Hashing might be redundant for certain PRNG implementations, but
 * only if the implementation already mixes seeds very well. (Similar seeds
 * can produce outputs with the same patterns.) If you use another RNG then
 * you need to bundle its source with your project. C's "srand" should not
 * be used because the same seed can produce different results on different 
 * platforms.
 */
public static long coordToLong(int x, int y)
{
  // Co-prime and odd multipliers
  return 0xf218258a20f6e313L * x + 0xa9d346a13008a355L * y;
}

public static long hash(long n)
{
  // Better magic numbers from David Stafford
  n ^= n >>> 31;
  n *= 0x7fb5d329728ea185L;
  n ^= n >>> 37;
  n *= 0x81dadef4bc2dd44dL;
  n ^= n >>> 33;
  return n;
}

public static SplittableRandom getSeededRng(int x, int y)
{
  long n = coordToLong(x, y);
  return new SplittableRandom(n);
}