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I'm trying to classify cifar10 images with Google colab TPU, according to the official tutorial.

However I got the following error.

UnimplementedError: 6 root error(s) found.

Without using TPU, I didn't see any error. Could someone share some advice?

Attached bellow is my code.

from tensorflow.keras.models import Model
from tensorflow.keras.preprocessing.image import ImageDataGenerator
from tensorflow.keras.applications.vgg16 import VGG16
import tensorflow as tf
import numpy as np

import os
import tensorflow_datasets as tfds

# preparing TPU
resolver = tf.distribute.cluster_resolver.TPUClusterResolver(tpu='')
tf.config.experimental_connect_to_cluster(resolver)
# This is the TPU initialization code that has to be at the beginning.
tf.tpu.experimental.initialize_tpu_system(resolver)
print("All devices: ", tf.config.list_logical_devices('TPU'))

strategy = tf.distribute.TPUStrategy(resolver)

# download cifar10 data
ds_test, ds_train = tfds.load('cifar10', split=['test', 'train'], )

# Preprocess the images
def resize_with_crop(ip):
    image = ip['image']
    label = ip['label']
    image = tf.expand_dims(image,0)
    label = tf.one_hot(label,10)
    label = tf.expand_dims(label,0)
    return (image, label)


ds_train_ = ds_train.map(resize_with_crop)
ds_test_ = ds_test.map(resize_with_crop)

with strategy.scope():
    model = VGG16(input_shape = (32, 32, 3), weights=None, classes=10)

    model.compile(optimizer='adam', loss = 'categorical_crossentropy', metrics= ['accuracy'])

    history = model.fit(ds_train_,
                        batch_size = 32,
                        steps_per_epoch = 64,
                        epochs = 1000,
                        validation_data = ds_test_,
                        shuffle = True,)

The error I got is bellow.

---------------------------------------------------------------------------
UnimplementedError                        Traceback (most recent call last)
<ipython-input-2-588bff080f0b> in <module>()
     25                         epochs = 1000,
     26                         validation_data = ds_test_,
---> 27                         shuffle = True,)
     28 
     29 '''

13 frames
/usr/local/lib/python3.7/dist-packages/keras/engine/training.py in fit(self, x, y, batch_size, epochs, verbose, callbacks, validation_split, validation_data, shuffle, class_weight, sample_weight, initial_epoch, steps_per_epoch, validation_steps, validation_batch_size, validation_freq, max_queue_size, workers, use_multiprocessing)
   1187               logs = tmp_logs  # No error, now safe to assign to logs.
   1188               end_step = step + data_handler.step_increment
-> 1189               callbacks.on_train_batch_end(end_step, logs)
   1190               if self.stop_training:
   1191                 break

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in on_train_batch_end(self, batch, logs)
    433     """
    434     if self._should_call_train_batch_hooks:
--> 435       self._call_batch_hook(ModeKeys.TRAIN, 'end', batch, logs=logs)
    436 
    437   def on_test_batch_begin(self, batch, logs=None):

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in _call_batch_hook(self, mode, hook, batch, logs)
    293       self._call_batch_begin_hook(mode, batch, logs)
    294     elif hook == 'end':
--> 295       self._call_batch_end_hook(mode, batch, logs)
    296     else:
    297       raise ValueError('Unrecognized hook: {}'.format(hook))

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in _call_batch_end_hook(self, mode, batch, logs)
    313       self._batch_times.append(batch_time)
    314 
--> 315     self._call_batch_hook_helper(hook_name, batch, logs)
    316 
    317     if len(self._batch_times) >= self._num_batches_for_timing_check:

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in _call_batch_hook_helper(self, hook_name, batch, logs)
    351     for callback in self.callbacks:
    352       hook = getattr(callback, hook_name)
--> 353       hook(batch, logs)
    354 
    355     if self._check_timing:

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in on_train_batch_end(self, batch, logs)
   1026 
   1027   def on_train_batch_end(self, batch, logs=None):
-> 1028     self._batch_update_progbar(batch, logs)
   1029 
   1030   def on_test_batch_end(self, batch, logs=None):

/usr/local/lib/python3.7/dist-packages/keras/callbacks.py in _batch_update_progbar(self, batch, logs)
   1098     if self.verbose == 1:
   1099       # Only block async when verbose = 1.
-> 1100       logs = tf_utils.sync_to_numpy_or_python_type(logs)
   1101       self.progbar.update(self.seen, list(logs.items()), finalize=False)
   1102 

/usr/local/lib/python3.7/dist-packages/keras/utils/tf_utils.py in sync_to_numpy_or_python_type(tensors)
    514     return t  # Don't turn ragged or sparse tensors to NumPy.
    515 
--> 516   return tf.nest.map_structure(_to_single_numpy_or_python_type, tensors)
    517 
    518 

/usr/local/lib/python3.7/dist-packages/tensorflow/python/util/nest.py in map_structure(func, *structure, **kwargs)
    867 
    868   return pack_sequence_as(
--> 869       structure[0], [func(*x) for x in entries],
    870       expand_composites=expand_composites)
    871 

/usr/local/lib/python3.7/dist-packages/tensorflow/python/util/nest.py in <listcomp>(.0)
    867 
    868   return pack_sequence_as(
--> 869       structure[0], [func(*x) for x in entries],
    870       expand_composites=expand_composites)
    871 

/usr/local/lib/python3.7/dist-packages/keras/utils/tf_utils.py in _to_single_numpy_or_python_type(t)
    510   def _to_single_numpy_or_python_type(t):
    511     if isinstance(t, tf.Tensor):
--> 512       x = t.numpy()
    513       return x.item() if np.ndim(x) == 0 else x
    514     return t  # Don't turn ragged or sparse tensors to NumPy.

/usr/local/lib/python3.7/dist-packages/tensorflow/python/framework/ops.py in numpy(self)
   1092     """
   1093     # TODO(slebedev): Consider avoiding a copy for non-CPU or remote tensors.
-> 1094     maybe_arr = self._numpy()  # pylint: disable=protected-access
   1095     return maybe_arr.copy() if isinstance(maybe_arr, np.ndarray) else maybe_arr
   1096 

/usr/local/lib/python3.7/dist-packages/tensorflow/python/framework/ops.py in _numpy(self)
   1060       return self._numpy_internal()
   1061     except core._NotOkStatusException as e:  # pylint: disable=protected-access
-> 1062       six.raise_from(core._status_to_exception(e.code, e.message), None)  # pylint: disable=protected-access
   1063 
   1064   @property

/usr/local/lib/python3.7/dist-packages/six.py in raise_from(value, from_value)

UnimplementedError: 6 root error(s) found.
  (0) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_2]]
  (1) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_6]]
  (2) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_3]]
     [[cluster_train_function/_execute_6_0/_187]]
  (3) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_3]]
     [[tpu_compile_succeeded_assert/_17093395999373799140/_5/_159]]
  (4) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_3]]
     [[tpu_compile_succeeded_assert/_17093395999373799140/_5/_111]]
  (5) Unimplemented: {{function_node __inference_train_function_127397}} File system scheme '[local]' not implemented (file: '/root/tensorflow_datasets/cifar10/3.0.2/cifar10-train.tfrecord-00000-of-00001')
     [[{{node MultiDeviceIteratorGetNextFromShard}}]]
     [[RemoteCall]]
     [[IteratorGetNext_3]]
0 successful operations.
3 derived errors ignored.

1 Answers1

0

if you look to the error, it says File system scheme '[local]' not implemented.

tfds often doesn't host all the datasets and downloads some from the original source to your local machine, which TPU can't access.

Cloud TPUs can only access data in GCS as only the GCS file system is registered. Please see: https://cloud.google.com/tpu/docs/troubleshooting#cannot_use_local_filesystem for more details.

You can make tfds to download the data to your gs bucket (details are here):

# Authenticate your account to access GCS.
from google.colab import auth
auth.authenticate_user()

...

# download cifar10 data to a gs bucket.
ds_test, ds_train = tfds.load('cifar10', split=['test', 'train'], try_gcs=True, data_dir="gs://YOUR_BUCKET_NAME")

Note that recently introduced TPU VMs can access local files. And you can create TPU VMs in GCP but not yet in Colab/Kaggle.

Gagik
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