Method initializeBackend

tfjs-core/src/engine.ts:319–369

* Initializes a backend by looking up the backend name in the factory * registry and calling the factory method. Returns a boolean representing * whether the initialization of the backend succeeded. Throws an error if * there is no backend in the factory registry.

(backendName: string)

   * there is no backend in the factory registry.
   */
  private initializeBackend(backendName: string):
      {success: boolean|Promise<boolean>, asyncInit: boolean} {
    const registryFactoryEntry = this.registryFactory[backendName];
    if (registryFactoryEntry == null) {
      throw new Error(
          `Cannot initialize backend ${backendName}, no registration found.`);
    }

    try {
      const backend = registryFactoryEntry.factory();
      /* Test if the factory returns a promise.
      Done in a more liberal way than
      previous 'Promise.resolve(backend)===backend'
      as we needed to account for custom Promise
      implementations (e.g. Angular) */
      if (backend && !(backend instanceof KernelBackend) &&
          typeof backend.then === 'function') {
        const promiseId = ++this.pendingBackendInitId;
        const success =
            backend
                .then(backendInstance => {
                  // Outdated promise. Another backend was set in the meantime.
                  if (promiseId < this.pendingBackendInitId) {
                    return false;
                  }
                  this.registry[backendName] = backendInstance;
                  this.pendingBackendInit = null;
                  return true;
                })
                .catch(err => {
                  // Outdated promise. Another backend was set in the meantime.
                  if (promiseId < this.pendingBackendInitId) {
                    return false;
                  }
                  this.pendingBackendInit = null;
                  log.warn(`Initialization of backend ${backendName} failed`);
                  log.warn(err.stack || err.message);
                  return false;
                });
        this.pendingBackendInit = success;
        return {success, asyncInit: true};
      } else {
        this.registry[backendName] = backend as KernelBackend;
        return {success: true, asyncInit: false};
      }
    } catch (err) {
      log.warn(`Initialization of backend ${backendName} failed`);
      log.warn(err.stack || err.message);
      return {success: false, asyncInit: false};
    }
  }

  removeBackend(backendName: string): void {
    if (!(backendName in this.registryFactory)) {