Function valueAndGrad

tfjs-core/src/gradients.ts:164–183

* Like `tf.grad`, but also returns the value of `f()`. Useful when `f()` * returns a metric you want to show. * * The result is a rich object with the following properties: * - grad: The gradient of `f(x)` w.r.t. `x` (result of `tf.grad`). * - value: The value returned by `f(x)`. * * ```js *

(f: (x: I) => O)

 * @doc {heading: 'Training', subheading: 'Gradients'}
 */
function valueAndGrad<I extends Tensor, O extends Tensor>(f: (x: I) => O): (
    x: I, dy?: O) => {
  value: O;
  grad: I;
} {
  util.assert(
      util.isFunction(f),
      () => 'The f passed in valueAndGrad(f) must be a function');
  return (x: I, dy?: O) => {
    util.assert(
        x instanceof Tensor,
        () => 'The x passed in valueAndGrad(f)(x) must be a tensor');
    util.assert(
        dy == null || dy instanceof Tensor,
        () => 'The dy passed in valueAndGrad(f)(x, dy) must be a tensor');
    const {grads, value} = ENGINE.gradients(() => f(x), [x], dy);
    checkGrads(grads);
    return {grad: grads[0] as I, value};
  };
}

/**
 * Like `tf.grads`, but returns also the value of `f()`. Useful when `f()`