molstar
Version:
A comprehensive macromolecular library.
113 lines (112 loc) • 3.88 kB
JavaScript
;
/**
* Copyright (c) 2024 mol* contributors, licensed under MIT, See LICENSE file for more info.
*
* @author Alexander Rose <alexander.rose@weirdbyte.de>
*
* This code has been modified from https://github.com/mrdoob/three.js/,
* copyright (c) 2010-2024 three.js authors. MIT License
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.toHalfFloat = toHalfFloat;
exports.fromHalfFloat = fromHalfFloat;
// Fast Half Float Conversions, http://www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
const interpolate_1 = require("../mol-math/interpolate");
const Tables = generateTables();
function generateTables() {
// float32 to float16 helpers
const buffer = new ArrayBuffer(4);
const floatView = new Float32Array(buffer);
const uint32View = new Uint32Array(buffer);
const baseTable = new Uint32Array(512);
const shiftTable = new Uint32Array(512);
for (let i = 0; i < 256; ++i) {
const e = i - 127;
if (e < -27) { // very small number (0, -0)
baseTable[i] = 0x0000;
baseTable[i | 0x100] = 0x8000;
shiftTable[i] = 24;
shiftTable[i | 0x100] = 24;
}
else if (e < -14) { // small number (denorm)
baseTable[i] = 0x0400 >> (-e - 14);
baseTable[i | 0x100] = (0x0400 >> (-e - 14)) | 0x8000;
shiftTable[i] = -e - 1;
shiftTable[i | 0x100] = -e - 1;
}
else if (e <= 15) { // normal number
baseTable[i] = (e + 15) << 10;
baseTable[i | 0x100] = ((e + 15) << 10) | 0x8000;
shiftTable[i] = 13;
shiftTable[i | 0x100] = 13;
}
else if (e < 128) { // large number (Infinity, -Infinity)
baseTable[i] = 0x7c00;
baseTable[i | 0x100] = 0xfc00;
shiftTable[i] = 24;
shiftTable[i | 0x100] = 24;
}
else { // stay (NaN, Infinity, -Infinity)
baseTable[i] = 0x7c00;
baseTable[i | 0x100] = 0xfc00;
shiftTable[i] = 13;
shiftTable[i | 0x100] = 13;
}
}
// float16 to float32 helpers
const mantissaTable = new Uint32Array(2048);
const exponentTable = new Uint32Array(64);
const offsetTable = new Uint32Array(64);
for (let i = 1; i < 1024; ++i) {
let m = i << 13; // zero pad mantissa bits
let e = 0; // zero exponent
// normalized
while ((m & 0x00800000) === 0) {
m <<= 1;
e -= 0x00800000; // decrement exponent
}
m &= ~0x00800000; // clear leading 1 bit
e += 0x38800000; // adjust bias
mantissaTable[i] = m | e;
}
for (let i = 1024; i < 2048; ++i) {
mantissaTable[i] = 0x38000000 + ((i - 1024) << 13);
}
for (let i = 1; i < 31; ++i) {
exponentTable[i] = i << 23;
}
exponentTable[31] = 0x47800000;
exponentTable[32] = 0x80000000;
for (let i = 33; i < 63; ++i) {
exponentTable[i] = 0x80000000 + ((i - 32) << 23);
}
exponentTable[63] = 0xc7800000;
for (let i = 1; i < 64; ++i) {
if (i !== 32) {
offsetTable[i] = 1024;
}
}
return {
floatView,
uint32View,
baseTable,
shiftTable,
mantissaTable,
exponentTable,
offsetTable
};
}
/** float32 to float16 */
function toHalfFloat(val) {
val = (0, interpolate_1.clamp)(val, -65504, 65504);
Tables.floatView[0] = val;
const f = Tables.uint32View[0];
const e = (f >> 23) & 0x1ff;
return Tables.baseTable[e] + ((f & 0x007fffff) >> Tables.shiftTable[e]);
}
/** float16 to float32 */
function fromHalfFloat(val) {
const m = val >> 10;
Tables.uint32View[0] = Tables.mantissaTable[Tables.offsetTable[m] + (val & 0x3ff)] + Tables.exponentTable[m];
return Tables.floatView[0];
}