Method getTensorsForGradient

tfjs-core/src/engine.ts:763–796

* Returns a list of tensors to save for a given gradient calculation. * * @param kernelName name of kernel to look up gradient for. * @param inputs a map of input tensors. * @param outputs an array of output tensors from forward mode of kernel.

(
      kernelName: string, inputs: NamedTensorMap,
      outputs: Tensor[])

   * @param outputs an array of output tensors from forward mode of kernel.
   */
  private getTensorsForGradient(
      kernelName: string, inputs: NamedTensorMap,
      outputs: Tensor[]): Tensor[]|null {
    const gradConfig = getGradient(kernelName);
    if (gradConfig != null) {
      const inputsToSave: string[] = gradConfig.inputsToSave || [];
      const outputsToSave: boolean[] = gradConfig.outputsToSave || [];

      // If saveAllInputs is true, all inputs will be saved. Otherwise, inputs
      // specified in inputsToSave will be saved.
      let inputTensorsToSave: Tensor[];
      if (gradConfig.saveAllInputs) {
        util.assert(
            Array.isArray(inputs),
            () => 'saveAllInputs is true, expected inputs to be an array.');

        inputTensorsToSave = Object.keys(inputs).map((key) => inputs[key]);
      } else {
        inputTensorsToSave = inputsToSave.map((inputName) => inputs[inputName]);
      }

      const outputTensorsToSave: Tensor[] =
          outputs.filter((_, i) => outputsToSave[i]);

      return inputTensorsToSave.concat(outputTensorsToSave);
    }
    // We return an empty list rather than throw an error because the kernel we
    // are looking up may not actually be relevant to backproping through the
    // overall function
    //
    // See 'does not error if irrelevant (pruned) ops are missing grads' test
    // in gradients_test.ts for an example.
    return [];
  }

  /**
   * Internal method used by public APIs for tensor creation. Makes a new