Multi-core simulation: grain movement and heat across a worker pool (t88 phase 3)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/loop.js

@@ -40,7 +40,13 @@ function frame(now) {
       GAME.padRun = pm > 0.92 ? GAME.padRun + 1 : 0;
       botStep(ix, iy, keys.has('Shift') || GAME.padRun > 24);
       toolTick();
-      const s0 = performance.now(); simTick(); const elapsed = performance.now() - s0;
+      const s0 = performance.now();
+      try { simTick(); }
+      catch (e) {
+        GAME.paused = true; acc = 0; console.error(e);
+        toast('The world stopped updating. Reload this world to try again.', {big:true}); break;
+      }
+      const elapsed = performance.now() - s0;
       simMs = simMs * 0.9 + elapsed * 0.1; frameSim += elapsed; frameSteps++;
       if (devPaused) devSteps--; else acc -= step;
       steps++;

src/ui/settings.js

@@ -29,6 +29,7 @@ const SET_TABS = {
     { note: 'Upscaling (DLSS, FSR), frame generation and hardware ray tracing need native graphics APIs that browsers do not expose. They are planned for the compiled build.' },
   ],
   Simulation: [
+    { k: 'workerCap', label: 'CPU workers', d: 'Maximum helpers for grains and heat. Applies when you next load a world.', type: 'range', min: 1, max: 16, step: 1, fmt: v => v },
     { k: 'simSpeed', label: 'Simulation speed', type: 'select', opts: [[0.5, '0.5×'], [1, '1×'], [2, '2×']] },
     { k: 'maxSteps', label: 'Catch-up steps per frame', d: 'How hard the game tries to keep real time when frames are slow.', type: 'range', min: 1, max: 4, step: 1, fmt: v => v },
     { note: 'The whole world keeps simulating, wherever you are. Your factories keep running when you fly away. Areas where nothing moves or changes temperature go to sleep and cost almost nothing; busy areas cost the same near you or far away.' },

src/ui/state.js

@@ -5,7 +5,7 @@
 const SET_DEFAULT = {
   zoom: 12, integerScale: true, renderScale: 1, uiScale: 1, fpsCap: 0, showPerf: false, shake: true, cameraSmooth: 0.7, cameraLead: true,
   look: 'smooth', lighting: 'full', lightEvery: 1, ambient: 0.12, daylight: 1, glow: 'low', grain: 1, incandescence: true, particles: true,
-  minimap: true, minimapZoom: 4, fog: true, thermalPalette: 'inferno', simSpeed: 1, maxSteps: 3,
+  minimap: true, minimapZoom: 4, fog: true, thermalPalette: 'inferno', simSpeed: 1, maxSteps: 3, workerCap: 16,
   volMaster: 0.8, volMusic: 0.5, volSfx: 0.8, muted: false, muteUnfocused: true,
   deadzone: 0.18, aimSpeed: 1, autosave: 3, cardSeconds: 9, cursorLabel: 'ores', sv: 2,
 };

src/ui/threads.js

@@ -0,0 +1,39 @@
+// Browser transport only; the simulation owns the schedule and shared state.
+let threadStarting = null;
+async function startThreads() {
+  const count = Math.max(1, Math.min(16, Math.floor(SET.workerCap) || 16, (navigator.hardwareConcurrency || 3) - 2));
+  if (simPool && simPool.world === mat && simPool.workers.length === count) return;
+  if (threadStarting) await threadStarting;
+  if (simPool && simPool.world === mat && simPool.workers.length === count) return;
+  threadStarting = (async () => {
+    if (simPool) for (const worker of simPool.workers) worker.terminate();
+    simPool = null;
+    if (!(mat.buffer instanceof SharedArrayBuffer)) throw Error('Shared memory is unavailable');
+    const url = URL.createObjectURL(new Blob([SIM_WORKER_SOURCE, '\nonmessage=e=>threadMessage(e.data);'], {type:'text/javascript'}));
+    const pool = { world: mat, workers: [], slots: [] };
+    try {
+      const ready = [];
+      for (let k = 0; k < count; k++) {
+        const worker = new Worker(url), slot = threadSlot();
+        pool.workers.push(worker); pool.slots.push(slot);
+        ready.push(new Promise((resolve,reject) => {
+          const deadline = performance.now() + 10000;
+          worker.onerror = e => {
+            const error = Error(e.message || 'Simulation worker failed');
+            threadFailure(slot, error); reject(error);
+          };
+          const poll = () => {
+            if (Atomics.load(slot.control,0)) resolve();
+            else if (performance.now() > deadline) reject(Error('Simulation worker startup timed out'));
+            else setTimeout(poll, 1);
+          };
+          poll();
+        }));
+        worker.postMessage({world:threadWorld(),slot});
+      }
+      await Promise.all(ready); simPool = pool;
+    } catch (e) { for (const worker of pool.workers) worker.terminate(); throw e; }
+    finally { URL.revokeObjectURL(url); }
+  })();
+  try { await threadStarting; } finally { threadStarting = null; }
+}

src/ui/title.js

@@ -1,6 +1,6 @@
 // Startup capabilities and title art.
 const REQUIRE_WEBGPU = true;
-const REQUIRE_THREADS = false;
+const REQUIRE_THREADS = true;
 const CAPS = { isolated: self.crossOriginIsolated === true, webgpu: false, adapterInfo: null, ready: false };
 async function checkCapabilities() {
   try {