feat(playground/nisps): recency & spatial weighted training in JS ML engine

Add Dataset.computeWeights() with three modes:
- global: exponential recency decay (newest examples weighted higher)
- local: spatial suppression of older examples near the current input
- combined: both applied together

IML and WasmIML now compute weights on every train() call using the
active mode. Exposes recencyBias, weightingMode, localRadius properties.
WASM worker path passes sampleWeights through to C++ via the new binding.

playground/js/nisps/dataset.js

@@ -37,6 +37,80 @@ export class Dataset {
     return this.labels;
   }
 
+  /**
+   * Compute per-sample training weights. Returns Float32Array normalized to sum to 1.
+   * @param {'global'|'local'|'combined'} mode
+   * @param {object} params
+   * @param {number} params.recencyBias - 0 = uniform, 1 = strong recency (global/combined)
+   * @param {number[]} [params.queryInput] - current input position (local/combined)
+   * @param {number} [params.radius] - spatial radius in input space (local/combined), default 0.15
+   * @returns {Float32Array} weights summing to 1
+   */
+  computeWeights(mode = 'global', params = {}) {
+    const n = this.features.length;
+    if (n === 0) return new Float32Array(0);
+    if (n === 1) return new Float32Array([1.0]);
+
+    const weights = new Float32Array(n).fill(1.0);
+
+    // Global recency: exponential decay — newest = 1, each older *= decay
+    if (mode === 'global' || mode === 'combined') {
+      const bias = params.recencyBias ?? 0.6;
+      if (bias > 0) {
+        // decay per step: at bias=1, decay=0.7 (newest ~10x oldest for 10 examples)
+        // at bias=0.5, decay=0.85 (gentler)
+        const decay = 1 - 0.3 * bias;
+        for (let i = n - 2; i >= 0; i--) {
+          weights[i] = weights[i + 1] * decay;
+        }
+      }
+    }
+
+    // Local recency: newer examples near the query suppress older nearby ones
+    if ((mode === 'local' || mode === 'combined') && params.queryInput) {
+      const query = params.queryInput;
+      const radius = params.radius ?? 0.15;
+      const radiusSq = radius * radius;
+
+      for (let i = 0; i < n; i++) {
+        const feat = this.features[i];
+        // Distance from this example to the query point
+        let distSq = 0;
+        for (let d = 0; d < feat.length; d++) {
+          const diff = feat[d] - (query[d] ?? 0);
+          distSq += diff * diff;
+        }
+
+        if (distSq < radiusSq) {
+          // Count newer examples also within the radius
+          const proximity = 1 - Math.sqrt(distSq) / radius; // 1 = on top, 0 = at edge
+          let newerNearby = 0;
+          for (let j = i + 1; j < n; j++) {
+            let djSq = 0;
+            for (let d = 0; d < feat.length; d++) {
+              const diff = feat[d] - this.features[j][d];
+              djSq += diff * diff;
+            }
+            if (djSq < radiusSq) newerNearby++;
+          }
+          // Suppress: more newer neighbors + closer to query = more suppression
+          if (newerNearby > 0) {
+            weights[i] *= Math.pow(1 - proximity, newerNearby);
+          }
+        }
+      }
+    }
+
+    // Normalize to sum to 1
+    let sum = 0;
+    for (let i = 0; i < n; i++) sum += weights[i];
+    if (sum > 0) {
+      for (let i = 0; i < n; i++) weights[i] /= sum;
+    }
+
+    return weights;
+  }
+
   get size() {
     return this.features.length;
   }

playground/js/nisps/iml.js

@@ -52,6 +52,9 @@ export class IML {
     this.lossHistory = [];
     this.totalTrainingIterations = 0;
     this.logFn = null;
+    this.recencyBias = 0.6;       // 0 = uniform, 1 = strong recency
+    this.weightingMode = 'global'; // 'global' | 'local' | 'combined'
+    this.localRadius = 0.15;      // input-space radius for local weighting
   }
 
   setLogger(fn) {
@@ -182,6 +185,12 @@ export class IML {
       return null;
     }
 
+    const sampleWeights = this.dataset.computeWeights(this.weightingMode, {
+      recencyBias: this.recencyBias,
+      queryInput: this.inputState,
+      radius: this.localRadius,
+    });
+
     this.log('Training...');
     this.lastLoss = this.mlp.train(
       features,
@@ -189,7 +198,7 @@ export class IML {
       this.learningRate,
       this.maxIterations,
       this.convergenceThreshold,
-      options
+      { ...options, sampleWeights }
     );
 
     const latestHistory = this.mlp.lastTrainingHistory || [];

playground/js/nisps/mlp.js

@@ -67,8 +67,10 @@ export class MLP {
   }
 
   // Per-sample SGD training (Train method from C++)
+  // sampleWeights: optional Float32Array of per-sample weights (normalized, sum to 1)
   train(features, labels, learningRate, maxIterations = 1000, minError = 0.00001, options = {}) {
     const sampleSizeRecip = 1 / features.length;
+    const sampleWeights = options.sampleWeights || null;
     let loss = 0;
     const history = [];
     const onIteration = typeof options.onIteration === 'function' ? options.onIteration : null;
@@ -77,10 +79,11 @@ export class MLP {
       loss = 0;
 
       for (let s = 0; s < features.length; s++) {
+        const weight = sampleWeights ? sampleWeights[s] : sampleSizeRecip;
         const { output, activations } = this.getOutput(features[s], false);
         const derivError = new Array(output.length);
 
-        loss += mseLoss(labels[s], output, derivError, sampleSizeRecip);
+        loss += mseLoss(labels[s], output, derivError, weight);
 
         // Backprop with direct weight update
         let tempDerivError = derivError;
@@ -90,7 +93,8 @@ export class MLP {
         }
       }
 
-      loss *= sampleSizeRecip;
+      // Custom weights already normalized — loss is already correctly scaled
+      if (!sampleWeights) loss *= sampleSizeRecip;
       history.push(loss);
 
       if (onIteration) onIteration(iter, loss);

playground/js/nisps/nisps-wasm-worker.js

@@ -18,7 +18,7 @@ async function ensureModule() {
     weightCount: mod.cwrap('nisps_mlp_weight_count', 'number', ['number']),
     getWeights: mod.cwrap('nisps_mlp_get_weights', null, ['number', 'number']),
     setWeights: mod.cwrap('nisps_mlp_set_weights', null, ['number', 'number']),
-    train: mod.cwrap('nisps_mlp_train', 'number', ['number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number']),
+    train: mod.cwrap('nisps_mlp_train', 'number', ['number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number']),
     alloc: mod.cwrap('nisps_alloc', 'number', ['number']),
     free: mod.cwrap('nisps_free', null, ['number']),
     allocInt: mod.cwrap('nisps_alloc_int', 'number', ['number']),
@@ -57,7 +57,7 @@ self.onmessage = async function(e) {
 
     const {
       layerSizes, activationIds, weights,
-      features, labels,
+      features, labels, sampleWeights,
       nInputs, nOutputs,
       learningRate, maxIterations, convergenceThreshold,
     } = payload;
@@ -97,16 +97,19 @@ self.onmessage = async function(e) {
 
     const featPtr = toHeapF32(featFlat);
     const labPtr = toHeapF32(labFlat);
+    const weightPtr = sampleWeights ? toHeapF32(new Float32Array(sampleWeights)) : 0;
 
     // Train
     const loss = w.train(
       mlp, featPtr, nSamples, featureDim,
       labPtr, nOutputs,
+      weightPtr,
       learningRate, maxIterations, convergenceThreshold
     );
 
     w.free(featPtr);
     w.free(labPtr);
+    if (weightPtr) w.free(weightPtr);
 
     // Extract trained weights
     const outPtr = w.alloc(weightCount);

playground/js/nisps/nisps-wasm.js

@@ -26,7 +26,7 @@ function wrapModule(mod) {
     getWeights: mod.cwrap('nisps_mlp_get_weights', null, ['number', 'number']),
     setWeights: mod.cwrap('nisps_mlp_set_weights', null, ['number', 'number']),
     inference: mod.cwrap('nisps_mlp_inference', null, ['number', 'number', 'number', 'number', 'number']),
-    train: mod.cwrap('nisps_mlp_train', 'number', ['number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number']),
+    train: mod.cwrap('nisps_mlp_train', 'number', ['number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number', 'number']),
     drawWeightsSpread: mod.cwrap('nisps_mlp_draw_weights_spread', null, ['number', 'number']),
     moveWeightsSpread: mod.cwrap('nisps_mlp_move_weights_spread', null, ['number', 'number', 'number']),
     alloc: mod.cwrap('nisps_alloc', 'number', ['number']),
@@ -86,6 +86,9 @@ export class WasmIML {
     this.maxIterations = maxIterations;
     this.learningRate = learningRate;
     this.convergenceThreshold = convergenceThreshold;
+    this.recencyBias = 0.6;       // 0 = uniform, 1 = strong recency
+    this.weightingMode = 'global'; // 'global' | 'local' | 'combined'
+    this.localRadius = 0.15;      // input-space radius for local weighting
 
     // Layer sizes: input+bias, hidden..., output
     const BIAS = 1;
@@ -221,15 +224,23 @@ export class WasmIML {
       this.weightsRandomised = false;
     }
 
-    const features = this.dataset.features;
-    const labels = this.dataset.labels;
-    if (features.length === 0) {
+    if (this.dataset.features.length === 0) {
       this.log('Empty dataset, skipping training.');
       return null;
     }
 
     this.log('Training...');
 
+    const features = this.dataset.features;
+    const labels = this.dataset.labels;
+
+    // Compute per-sample weights
+    const sampleWeights = this.dataset.computeWeights(this.weightingMode, {
+      recencyBias: this.recencyBias,
+      queryInput: this.inputState,
+      radius: this.localRadius,
+    });
+
     // Build flat arrays with bias appended to features
     const featureDim = this.nInputs + 1; // +bias
     const nSamples = features.length;
@@ -248,15 +259,18 @@ export class WasmIML {
 
     const featPtr = toHeapF32(this._w, featFlat);
     const labPtr = toHeapF32(this._w, labFlat);
+    const weightPtr = toHeapF32(this._w, sampleWeights);
 
     const loss = this._w.train(
       this._mlp, featPtr, nSamples, featureDim,
       labPtr, this.nOutputs,
+      weightPtr,
       this.learningRate, this.maxIterations, this.convergenceThreshold
     );
 
     this._w.free(featPtr);
     this._w.free(labPtr);
+    this._w.free(weightPtr);
 
     this.lastLoss = loss;
     // We don't have per-iteration history from WASM (single return value),
@@ -374,6 +388,11 @@ export class WasmIML {
     const flatWeights = this._getFlatWeights();
     const features = this.dataset.features;
     const labels = this.dataset.labels;
+    const sampleWeights = Array.from(this.dataset.computeWeights(this.weightingMode, {
+      recencyBias: this.recencyBias,
+      queryInput: this.inputState,
+      radius: this.localRadius,
+    }));
 
     // Lazy-init worker
     if (!this._worker) {
@@ -418,6 +437,7 @@ export class WasmIML {
           weights: flatWeights,
           features,
           labels,
+          sampleWeights,
           nInputs: this.nInputs,
           nOutputs: this.nOutputs,
           learningRate: this.learningRate,