import type { MatmulMethod } from './types'

// Plain triple loop, ikj order (row of A and row of C stay hot across the
// inner loop) — the "no special effort" baseline the other methods are
// measured against.
function multiply(a: Float64Array, b: Float64Array, n: number): Float64Array {
  const c = new Float64Array(n * n)
  for (let i = 0; i < n; i++) {
    const ai = i * n
    for (let k = 0; k < n; k++) {
      const aik = a[ai + k]
      if (aik === 0) continue
      const bk = k * n
      for (let j = 0; j < n; j++) {
        c[ai + j] += aik * b[bk + j]
      }
    }
  }
  return c
}

export const jsMatmul: MatmulMethod = {
  id: 'js',
  label: 'JavaScript/TS',
  precision: 'f64',
  worker: true,
  available: () => true,
  async run(n, a, b) {
    const t0 = performance.now()
    const c = multiply(a, b, n)
    const ms = performance.now() - t0
    return { ms, sample: c[0] }
  },
}