Ascii.Kit.Hash (Ascii v0.3.0)

The integer hashes that many upstream pieces share, word for word.

Each returns upstream's value: a float in [0, 1) or, for distro/3, the unsigned integer. Arguments may be integers or floats (truncated, as JS's Math.imul and | 0 truncate). They run in unsigned arithmetic with the multiply inlined, since ^, >>>, + and Math.imul agree modulo 2^32 whatever the signs; that makes them several times faster than the same steps through Ascii.Int32, which matters for scenes that hash tens of thousands of times a frame.

A piece whose hash is not one of these writes its own with Ascii.Int32.

Summary

Functions

distro(x, y, k)

The distros' scan noise, as an unsigned integer

murmur(x, y)

A murmur-style hash of two (aurora, doom-fire, lightning, saptarishi, aquarium, campfire, cherry-blossom)

murmur(a, b, c)

The same of three (sunrise, tv-static, wind)

scene(x, y)

The scenes' hash (night-coast, alpine-dawn and every other scene, and dissolve)

short(x, y)

One round of the murmur-style hash (lighthouse, train, windmill, fractal-tree, landscape)

Functions

distro(x, y, k)

@spec distro(x :: number(), y :: number(), k :: number()) :: non_neg_integer()

The distros' scan noise, as an unsigned integer:

let h = Math.imul(x, 73856093) ^ Math.imul(y, 19349663) ^ Math.imul(k, 83492791);
h = Math.imul(h ^ (h >>> 13), 1274126177);
return (h ^ (h >>> 16)) >>> 0;

murmur(x, y)

@spec murmur(x :: number(), y :: number()) :: float()

A murmur-style hash of two (aurora, doom-fire, lightning, saptarishi, aquarium, campfire, cherry-blossom):

let h = Math.imul(x, 0x27d4eb2d) ^ Math.imul(y, 0x165667b1);
h = Math.imul(h ^ (h >>> 15), 0x85ebca6b);
h = Math.imul(h ^ (h >>> 13), 0xc2b2ae35);
return ((h ^ (h >>> 16)) >>> 0) / 4294967296;

murmur(a, b, c)

@spec murmur(a :: number(), b :: number(), c :: number()) :: float()

The same of three (sunrise, tv-static, wind):

let h = Math.imul(a, 0x27d4eb2d) ^ Math.imul(b, 0x165667b1) ^ Math.imul(c, 0x2545f491);

then as murmur/2.

scene(x, y)

@spec scene(x :: number(), y :: number()) :: float()

The scenes' hash (night-coast, alpine-dawn and every other scene, and dissolve):

let h = Math.imul(x | 0, 374761393) + Math.imul(y | 0, 668265263);
h = Math.imul(h ^ (h >>> 13), 1274126177);
return ((h ^ (h >>> 16)) >>> 0) / 4294967296;

short(x, y)

@spec short(x :: number(), y :: number()) :: float()

One round of the murmur-style hash (lighthouse, train, windmill, fractal-tree, landscape):

let h = Math.imul(x, 0x27d4eb2d) ^ Math.imul(y, 0x165667b1);
h = Math.imul(h ^ (h >>> 15), 0x85ebca6b);
return ((h ^ (h >>> 13)) >>> 0) / 4294967296;