Metabolism: decision-cadence (think slower than you move) + empty-block skip; flat typed-array bytecode; WebGPU decision-layer slice (experimental) + heavy-world benchmark

metabolism/tools/bench.js

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+// The heavy-world benchmark: same song, same seed, same planted population —
+// only the decision cadence varies. Sim-only (no render), field 128.
+import { buildSong } from '../src/song/song.js';
+import { analyse } from '../src/audio/analyse.js';
+import { decodeWav, mono } from '../src/audio/wav.js';
+import { World } from '../src/sim/world.js';
+import { readFileSync } from 'node:fs';
+
+const name = process.argv[2] ?? 'runner';
+const frames = Number(process.argv[3] ?? 300);
+const wav = decodeWav(readFileSync(new URL(`../../flow-state/test/songs/${name}.wav`, import.meta.url)));
+const song = buildSong(analyse(mono(wav.channels), wav.sampleRate), 12345);
+
+function plant(w) {
+    // identical starting points: a dense 80×80 metropolis west of centre
+    const F = w.field;
+    for (let y = 24; y < 104; y++) {
+        for (let x = 24; x < 104; x++) {
+            const i = y * F + x;
+            for (let s = 0; s < w.m; s++) w.pop[s][i] = 1.6;
+        }
+    }
+    w.recount();
+}
+
+for (const vmEvery of [1, 2, 3]) {
+    const w = new World(song, { fps: 30, field: 128, genesis: 0, vmEvery });
+    plant(w);
+    const start = w.count;
+    // warm-up
+    for (let f = 0; f < 30; f++) w.step();
+    const t0 = process.hrtime.bigint();
+    for (let f = 0; f < frames; f++) w.step();
+    const ms = Number(process.hrtime.bigint() - t0) / 1e6 / frames;
+    console.log(`vmEvery=${vmEvery}  sim ${ms.toFixed(1)} ms/frame  (start ${Math.round(start)}, now ${Math.round(w.count)}, peak-ish budget ${Math.round(w.cap).toLocaleString()})`);
+}