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Combine tallying of buckets for both passes of float32 sorting (#132)

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This commit is contained in:
Noeri Huisman
2025-07-23 15:49:00 +02:00
committed by GitHub
parent c1a335e8ee
commit 9b6ea3c987
2 changed files with 48 additions and 43 deletions
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src/worker.ts
+24 -22
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@@ -527,7 +527,8 @@ function sortDoubleSplats({
}
const DEPTH_INFINITY_F32 = 0x7f800000;
let bucket16: Uint32Array | null = null;
let bucket16lo: Uint32Array | null = null;
let bucket16hi: Uint32Array | null = null;
let scratchSplats: Uint32Array | null = null;
// two-pass radix sort (base 65536) of 32-bit keys in readback,
@@ -546,29 +547,36 @@ function sort32Splats({
const BASE = 1 << 16; // 65536
// allocate once
if (!bucket16) {
bucket16 = new Uint32Array(BASE);
if (!bucket16lo) {
bucket16lo = new Uint32Array(BASE);
}
if (!bucket16hi) {
bucket16hi = new Uint32Array(BASE);
}
if (!scratchSplats || scratchSplats.length < maxSplats) {
scratchSplats = new Uint32Array(maxSplats);
}
//
// ——— Pass #1: bucket by inv(lo 16 bits) ———
//
bucket16.fill(0);
// tally low and high buckets
bucket16lo.fill(0);
bucket16hi.fill(0);
for (let i = 0; i < numSplats; ++i) {
const key = readback[i];
if (key < DEPTH_INFINITY_F32) {
const inv = ~key >>> 0;
bucket16[inv & 0xffff] += 1;
bucket16lo[inv & 0xffff] += 1;
bucket16hi[inv >>> 16] += 1;
}
}
//
// ——— Pass #1: bucket by inv(lo 16 bits) ———
//
// exclusive prefix‑sum → starting offsets
let total = 0;
for (let b = 0; b < BASE; ++b) {
const c = bucket16[b];
bucket16[b] = total;
const c = bucket16lo[b];
bucket16lo[b] = total;
total += c;
}
const activeSplats = total;
@@ -578,24 +586,18 @@ function sort32Splats({
const key = readback[i];
if (key < DEPTH_INFINITY_F32) {
const inv = ~key >>> 0;
scratchSplats[bucket16[inv & 0xffff]++] = i;
scratchSplats[bucket16lo[inv & 0xffff]++] = i;
}
}
//
// ——— Pass #2: bucket by inv(hi 16 bits) ———
//
bucket16.fill(0);
for (let k = 0; k < activeSplats; ++k) {
const idx = scratchSplats[k];
const inv = ~readback[idx] >>> 0;
bucket16[inv >>> 16] += 1;
}
// exclusive prefix‑sum again
let sum = 0;
for (let b = 0; b < BASE; ++b) {
const c = bucket16[b];
bucket16[b] = sum;
const c = bucket16hi[b];
bucket16hi[b] = sum;
sum += c;
}
@@ -603,13 +605,13 @@ function sort32Splats({
for (let k = 0; k < activeSplats; ++k) {
const idx = scratchSplats[k];
const inv = ~readback[idx] >>> 0;
ordering[bucket16[inv >>> 16]++] = idx;
ordering[bucket16hi[inv >>> 16]++] = idx;
}
// sanity‑check: the last bucket should have eaten all entries
if (bucket16[BASE - 1] !== activeSplats) {
if (bucket16hi[BASE - 1] !== activeSplats) {
throw new Error(
`Expected ${activeSplats} active splats but got ${bucket16[BASE - 1]}`,
`Expected ${activeSplats} active splats but got ${bucket16hi[BASE - 1]}`,
);
}