[system-a] gradientDescentVelocity

- `velocityRepresentation` -- takes `options: { relayFactor }`

TODO.md

@@ -1,7 +1,5 @@
 # system-a
 
-[system-a] `velocityRepresentation` -- takes `options: { velocityAccumulationFactor }`
-[system-a] `gradientDescentVelocity`
 [system-a] targets test `gradientDescentVelocity`
 
 # question

src/system-a/gradient-descent/gradientDescentVelocity.ts

@@ -1,22 +1,25 @@
 import { tensorZeros, type Tensor } from "../tensor/index.js"
-import { mul, sub } from "../toys/index.js"
+import { add, mul, sub } from "../toys/index.js"
 import type { Representation } from "./Representation.js"
 import { gradientDescent } from "./gradientDescent.js"
 
 export function velocityRepresentation(options: {
   learningRate: number
-  velocityAccumulationFactor: number
+  relayFactor: number
 }): Representation<[Tensor, Tensor]> {
   return {
     inflate: (p) => [p, tensorZeros(p)],
     deflate: ([p, _]) => p,
-    update: ([p], g) => [sub(p, mul(options.learningRate, g))],
+    update: ([p, w], g) => {
+      const v = sub(mul(w, options.relayFactor), mul(g, options.learningRate))
+      return [add(p, v), v]
+    },
   }
 }
 
 export function gradientDescentVelocity(options: {
   learningRate: number
-  velocityAccumulationFactor: number
+  relayFactor: number
 }) {
   return gradientDescent(velocityRepresentation(options))
 }