agentfootprint/dist/memory/embedding/cosine.js

The explainable agent framework — backtrack a wrong answer to the exact context that caused it (evidence, not guesses). Built on footprintjs.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.cosineSimilarity = void 0;
/**
 * cosineSimilarity — the similarity metric used by `store.search()`.
 *
 *   cos(a, b) = dot(a, b) / (||a|| * ||b||)
 *
 * Range: [-1, 1]. Equal-direction vectors → 1. Orthogonal → 0.
 * Opposite → -1.
 *
 * Zero-magnitude handling: if either vector is all-zero (or the empty
 * vector), returns 0 — never NaN. NaN in a similarity score would
 * poison downstream picker comparisons (NaN < x is false for all x)
 * and silently demote the entry. Explicit 0 is safer.
 *
 * Length mismatch THROWS: comparing vectors of different dimensions
 * is almost always a bug (different embedders mixed in the same store).
 * Fail loud rather than silently truncate.
 */
function cosineSimilarity(a, b) {
    if (a.length !== b.length) {
        throw new Error(`cosineSimilarity: vector length mismatch — ${a.length} vs ${b.length}. ` +
            'Check that all entries in the store were produced by the SAME embedder instance.');
    }
    if (a.length === 0)
        return 0;
    let dot = 0;
    let magA = 0;
    let magB = 0;
    for (let i = 0; i < a.length; i++) {
        const av = a[i];
        const bv = b[i];
        dot += av * bv;
        magA += av * av;
        magB += bv * bv;
    }
    if (magA === 0 || magB === 0)
        return 0;
    return dot / (Math.sqrt(magA) * Math.sqrt(magB));
}
exports.cosineSimilarity = cosineSimilarity;
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