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Model progress can be saved during and after training. This means a model can resume where it left off and avoid long training times. Saving also means you can share your model and others can recreate your work. When publishing research models and techniques, most machine learning practitioners share:

- code to create the model, and
- the trained weights, or parameters, for the model

Sharing this data helps others understand how the model works and try it themselves with new data.

### Options

There are different ways to save TensorFlow models depending on the API you're using. This guide uses tf.keras, a high-level API to build and train models in TensorFlow. For other approaches see the TensorFlow Save and Restore guide or Saving in eager.

## Setup

### Installs and imports

Install and import TensorFlow and dependencies:

`pip install -q pyyaml h5py # Required to save models in HDF5 format`

```
import os
import tensorflow as tf
from tensorflow import keras
print(tf.version.VERSION)
```

2.4.1

### Get an example dataset

To demonstrate how to save and load weights, you'll use the MNIST dataset. To speed up these runs, use the first 1000 examples:

```
(train_images, train_labels), (test_images, test_labels) = tf.keras.datasets.mnist.load_data()
train_labels = train_labels[:1000]
test_labels = test_labels[:1000]
train_images = train_images[:1000].reshape(-1, 28 * 28) / 255.0
test_images = test_images[:1000].reshape(-1, 28 * 28) / 255.0
```

Downloading data from https://storage.googleapis.com/tensorflow/tf-keras-datasets/mnist.npz 11493376/11490434 [==============================] - 0s 0us/step

### Define a model

Start by building a simple sequential model:

```
# Define a simple sequential model
def create_model():
model = tf.keras.models.Sequential([
keras.layers.Dense(512, activation='relu', input_shape=(784,)),
keras.layers.Dropout(0.2),
keras.layers.Dense(10)
])
model.compile(optimizer='adam',
loss=tf.losses.SparseCategoricalCrossentropy(from_logits=True),
metrics=[tf.metrics.SparseCategoricalAccuracy()])
return model
# Create a basic model instance
model = create_model()
# Display the model's architecture
model.summary()
```

Model: "sequential" _________________________________________________________________ Layer (type) Output Shape Param # ================================================================= dense (Dense) (None, 512) 401920 _________________________________________________________________ dropout (Dropout) (None, 512) 0 _________________________________________________________________ dense_1 (Dense) (None, 10) 5130 ================================================================= Total params: 407,050 Trainable params: 407,050 Non-trainable params: 0 _________________________________________________________________

## Save checkpoints during training

You can use a trained model without having to retrain it, or pick-up training where you left off in case the training process was interrupted. The `tf.keras.callbacks.ModelCheckpoint`

callback allows you to continually save the model both *during* and at *the end* of training.

### Checkpoint callback usage

Create a `tf.keras.callbacks.ModelCheckpoint`

callback that saves weights only during training:

```
checkpoint_path = "training_1/cp.ckpt"
checkpoint_dir = os.path.dirname(checkpoint_path)
# Create a callback that saves the model's weights
cp_callback = tf.keras.callbacks.ModelCheckpoint(filepath=checkpoint_path,
save_weights_only=True,
verbose=1)
# Train the model with the new callback
model.fit(train_images,
train_labels,
epochs=10,
validation_data=(test_images, test_labels),
callbacks=[cp_callback]) # Pass callback to training
# This may generate warnings related to saving the state of the optimizer.
# These warnings (and similar warnings throughout this notebook)
# are in place to discourage outdated usage, and can be ignored.
```

Epoch 1/10 32/32 [==============================] - 1s 14ms/step - loss: 1.6718 - sparse_categorical_accuracy: 0.4717 - val_loss: 0.7284 - val_sparse_categorical_accuracy: 0.7810 Epoch 00001: saving model to training_1/cp.ckpt Epoch 2/10 32/32 [==============================] - 0s 4ms/step - loss: 0.4771 - sparse_categorical_accuracy: 0.8706 - val_loss: 0.5380 - val_sparse_categorical_accuracy: 0.8350 Epoch 00002: saving model to training_1/cp.ckpt Epoch 3/10 32/32 [==============================] - 0s 4ms/step - loss: 0.2798 - sparse_categorical_accuracy: 0.9223 - val_loss: 0.4721 - val_sparse_categorical_accuracy: 0.8490 Epoch 00003: saving model to training_1/cp.ckpt Epoch 4/10 32/32 [==============================] - 0s 4ms/step - loss: 0.1965 - sparse_categorical_accuracy: 0.9597 - val_loss: 0.4343 - val_sparse_categorical_accuracy: 0.8550 Epoch 00004: saving model to training_1/cp.ckpt Epoch 5/10 32/32 [==============================] - 0s 4ms/step - loss: 0.1510 - sparse_categorical_accuracy: 0.9667 - val_loss: 0.4308 - val_sparse_categorical_accuracy: 0.8660 Epoch 00005: saving model to training_1/cp.ckpt Epoch 6/10 32/32 [==============================] - 0s 4ms/step - loss: 0.1140 - sparse_categorical_accuracy: 0.9845 - val_loss: 0.4052 - val_sparse_categorical_accuracy: 0.8680 Epoch 00006: saving model to training_1/cp.ckpt Epoch 7/10 32/32 [==============================] - 0s 4ms/step - loss: 0.0908 - sparse_categorical_accuracy: 0.9838 - val_loss: 0.4120 - val_sparse_categorical_accuracy: 0.8660 Epoch 00007: saving model to training_1/cp.ckpt Epoch 8/10 32/32 [==============================] - 0s 4ms/step - loss: 0.0632 - sparse_categorical_accuracy: 0.9936 - val_loss: 0.4178 - val_sparse_categorical_accuracy: 0.8600 Epoch 00008: saving model to training_1/cp.ckpt Epoch 9/10 32/32 [==============================] - 0s 4ms/step - loss: 0.0526 - sparse_categorical_accuracy: 0.9991 - val_loss: 0.3975 - val_sparse_categorical_accuracy: 0.8680 Epoch 00009: saving model to training_1/cp.ckpt Epoch 10/10 32/32 [==============================] - 0s 4ms/step - loss: 0.0391 - sparse_categorical_accuracy: 1.0000 - val_loss: 0.4106 - val_sparse_categorical_accuracy: 0.8660 Epoch 00010: saving model to training_1/cp.ckpt <tensorflow.python.keras.callbacks.History at 0x7f54502f6128>

This creates a single collection of TensorFlow checkpoint files that are updated at the end of each epoch:

```
os.listdir(checkpoint_dir)
```

['checkpoint', 'cp.ckpt.data-00000-of-00001', 'cp.ckpt.index']

As long as two models share the same architecture you can share weights between them. So, when restoring a model from weights-only, create a model with the same architecture as the original model and then set its weights.

Now rebuild a fresh, untrained model and evaluate it on the test set. An untrained model will perform at chance levels (~10% accuracy):

```
# Create a basic model instance
model = create_model()
# Evaluate the model
loss, acc = model.evaluate(test_images, test_labels, verbose=2)
print("Untrained model, accuracy: {:5.2f}%".format(100 * acc))
```

32/32 - 0s - loss: 2.3199 - sparse_categorical_accuracy: 0.1070 Untrained model, accuracy: 10.70%

Then load the weights from the checkpoint and re-evaluate:

```
# Loads the weights
model.load_weights(checkpoint_path)
# Re-evaluate the model
loss, acc = model.evaluate(test_images, test_labels, verbose=2)
print("Restored model, accuracy: {:5.2f}%".format(100 * acc))
```

32/32 - 0s - loss: 0.4106 - sparse_categorical_accuracy: 0.8660 Restored model, accuracy: 86.60%

### Checkpoint callback options

The callback provides several options to provide unique names for checkpoints and adjust the checkpointing frequency.

Train a new model, and save uniquely named checkpoints once every five epochs:

```
# Include the epoch in the file name (uses `str.format`)
checkpoint_path = "training_2/cp-{epoch:04d}.ckpt"
checkpoint_dir = os.path.dirname(checkpoint_path)
batch_size = 32
# Create a callback that saves the model's weights every 5 epochs
cp_callback = tf.keras.callbacks.ModelCheckpoint(
filepath=checkpoint_path,
verbose=1,
save_weights_only=True,
save_freq=5*batch_size)
# Create a new model instance
model = create_model()
# Save the weights using the `checkpoint_path` format
model.save_weights(checkpoint_path.format(epoch=0))
# Train the model with the new callback
model.fit(train_images,
train_labels,
epochs=50,
batch_size=batch_size,
callbacks=[cp_callback],
validation_data=(test_images, test_labels),
verbose=0)
```

WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.iter WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.beta_1 WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.beta_2 WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.decay WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.learning_rate WARNING:tensorflow:A checkpoint was restored (e.g. tf.train.Checkpoint.restore or tf.keras.Model.load_weights) but not all checkpointed values were used. See above for specific issues. Use expect_partial() on the load status object, e.g. tf.train.Checkpoint.restore(...).expect_partial(), to silence these warnings, or use assert_consumed() to make the check explicit. See https://www.tensorflow.org/guide/checkpoint#loading_mechanics for details. Epoch 00005: saving model to training_2/cp-0005.ckpt Epoch 00010: saving model to training_2/cp-0010.ckpt Epoch 00015: saving model to training_2/cp-0015.ckpt Epoch 00020: saving model to training_2/cp-0020.ckpt Epoch 00025: saving model to training_2/cp-0025.ckpt Epoch 00030: saving model to training_2/cp-0030.ckpt Epoch 00035: saving model to training_2/cp-0035.ckpt Epoch 00040: saving model to training_2/cp-0040.ckpt Epoch 00045: saving model to training_2/cp-0045.ckpt Epoch 00050: saving model to training_2/cp-0050.ckpt <tensorflow.python.keras.callbacks.History at 0x7f544fe8ffd0>

Now, look at the resulting checkpoints and choose the latest one:

```
os.listdir(checkpoint_dir)
```

['cp-0035.ckpt.index', 'cp-0010.ckpt.data-00000-of-00001', 'cp-0025.ckpt.index', 'cp-0035.ckpt.data-00000-of-00001', 'checkpoint', 'cp-0015.ckpt.data-00000-of-00001', 'cp-0050.ckpt.data-00000-of-00001', 'cp-0040.ckpt.data-00000-of-00001', 'cp-0005.ckpt.index', 'cp-0005.ckpt.data-00000-of-00001', 'cp-0020.ckpt.data-00000-of-00001', 'cp-0045.ckpt.index', 'cp-0010.ckpt.index', 'cp-0045.ckpt.data-00000-of-00001', 'cp-0030.ckpt.index', 'cp-0000.ckpt.index', 'cp-0015.ckpt.index', 'cp-0025.ckpt.data-00000-of-00001', 'cp-0030.ckpt.data-00000-of-00001', 'cp-0000.ckpt.data-00000-of-00001', 'cp-0020.ckpt.index', 'cp-0050.ckpt.index', 'cp-0040.ckpt.index']

```
latest = tf.train.latest_checkpoint(checkpoint_dir)
latest
```

'training_2/cp-0050.ckpt'

To test, reset the model and load the latest checkpoint:

```
# Create a new model instance
model = create_model()
# Load the previously saved weights
model.load_weights(latest)
# Re-evaluate the model
loss, acc = model.evaluate(test_images, test_labels, verbose=2)
print("Restored model, accuracy: {:5.2f}%".format(100 * acc))
```

32/32 - 0s - loss: 0.4639 - sparse_categorical_accuracy: 0.8770 Restored model, accuracy: 87.70%

## What are these files?

The above code stores the weights to a collection of checkpoint-formatted files that contain only the trained weights in a binary format. Checkpoints contain:

- One or more shards that contain your model's weights.
- An index file that indicates which weights are stored in which shard.

If you are training a model on a single machine, you'll have one shard with the suffix: `.data-00000-of-00001`

## Manually save weights

Manually saving weights with the `Model.save_weights`

method. By default, `tf.keras`

—and `save_weights`

in particular—uses the TensorFlow checkpoint format with a `.ckpt`

extension (saving in HDF5 with a `.h5`

extension is covered in the Save and serialize models guide):

```
# Save the weights
model.save_weights('./checkpoints/my_checkpoint')
# Create a new model instance
model = create_model()
# Restore the weights
model.load_weights('./checkpoints/my_checkpoint')
# Evaluate the model
loss, acc = model.evaluate(test_images, test_labels, verbose=2)
print("Restored model, accuracy: {:5.2f}%".format(100 * acc))
```

WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.iter WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.beta_1 WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.beta_2 WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.decay WARNING:tensorflow:Unresolved object in checkpoint: (root).optimizer.learning_rate WARNING:tensorflow:A checkpoint was restored (e.g. tf.train.Checkpoint.restore or tf.keras.Model.load_weights) but not all checkpointed values were used. See above for specific issues. Use expect_partial() on the load status object, e.g. tf.train.Checkpoint.restore(...).expect_partial(), to silence these warnings, or use assert_consumed() to make the check explicit. See https://www.tensorflow.org/guide/checkpoint#loading_mechanics for details. 32/32 - 0s - loss: 0.4639 - sparse_categorical_accuracy: 0.8770 Restored model, accuracy: 87.70%

## Save the entire model

Call `model.save`

to save a model's architecture, weights, and training configuration in a single file/folder. This allows you to export a model so it can be used without access to the original Python code*. Since the optimizer-state is recovered, you can resume training from exactly where you left off.

An entire model can be saved in two different file formats (`SavedModel`

and `HDF5`

). The TensorFlow `SavedModel`

format is the default file format in TF2.x. However, models can be saved in `HDF5`

format. More details on saving entire models in the two file formats is described below.

Saving a fully-functional model is very useful—you can load them in TensorFlow.js (Saved Model, HDF5) and then train and run them in web browsers, or convert them to run on mobile devices using TensorFlow Lite (Saved Model, HDF5)

*Custom objects (e.g. subclassed models or layers) require special attention when saving and loading. See the **Saving custom objects** section below

### SavedModel format

The SavedModel format is another way to serialize models. Models saved in this format can be restored using `tf.keras.models.load_model`

and are compatible with TensorFlow Serving. The SavedModel guide goes into detail about how to serve/inspect the SavedModel. The section below illustrates the steps to save and restore the model.

```
# Create and train a new model instance.
model = create_model()
model.fit(train_images, train_labels, epochs=5)
# Save the entire model as a SavedModel.
!mkdir -p saved_model
model.save('saved_model/my_model')
```

Epoch 1/5 32/32 [==============================] - 0s 2ms/step - loss: 1.5348 - sparse_categorical_accuracy: 0.5511 Epoch 2/5 32/32 [==============================] - 0s 2ms/step - loss: 0.4735 - sparse_categorical_accuracy: 0.8777 Epoch 3/5 32/32 [==============================] - 0s 2ms/step - loss: 0.2538 - sparse_categorical_accuracy: 0.9408 Epoch 4/5 32/32 [==============================] - 0s 2ms/step - loss: 0.2100 - sparse_categorical_accuracy: 0.9483 Epoch 5/5 32/32 [==============================] - 0s 2ms/step - loss: 0.1559 - sparse_categorical_accuracy: 0.9679 INFO:tensorflow:Assets written to: saved_model/my_model/assets

The SavedModel format is a directory containing a protobuf binary and a TensorFlow checkpoint. Inspect the saved model directory:

`# my_model directory`

`ls saved_model`

`# Contains an assets folder, saved_model.pb, and variables folder.`

`ls saved_model/my_model`

my_model assets saved_model.pb variables

Reload a fresh Keras model from the saved model:

```
new_model = tf.keras.models.load_model('saved_model/my_model')
# Check its architecture
new_model.summary()
```

Model: "sequential_5" _________________________________________________________________ Layer (type) Output Shape Param # ================================================================= dense_10 (Dense) (None, 512) 401920 _________________________________________________________________ dropout_5 (Dropout) (None, 512) 0 _________________________________________________________________ dense_11 (Dense) (None, 10) 5130 ================================================================= Total params: 407,050 Trainable params: 407,050 Non-trainable params: 0 _________________________________________________________________

The restored model is compiled with the same arguments as the original model. Try running evaluate and predict with the loaded model:

```
# Evaluate the restored model
loss, acc = new_model.evaluate(test_images, test_labels, verbose=2)
print('Restored model, accuracy: {:5.2f}%'.format(100 * acc))
print(new_model.predict(test_images).shape)
```

32/32 - 0s - loss: 0.4454 - sparse_categorical_accuracy: 0.8500 Restored model, accuracy: 85.00% (1000, 10)

### HDF5 format

Keras provides a basic save format using the HDF5 standard.

```
# Create and train a new model instance.
model = create_model()
model.fit(train_images, train_labels, epochs=5)
# Save the entire model to a HDF5 file.
# The '.h5' extension indicates that the model should be saved to HDF5.
model.save('my_model.h5')
```

Epoch 1/5 32/32 [==============================] - 0s 2ms/step - loss: 1.6127 - sparse_categorical_accuracy: 0.5163 Epoch 2/5 32/32 [==============================] - 0s 2ms/step - loss: 0.4528 - sparse_categorical_accuracy: 0.8731 Epoch 3/5 32/32 [==============================] - 0s 2ms/step - loss: 0.2975 - sparse_categorical_accuracy: 0.9306 Epoch 4/5 32/32 [==============================] - 0s 2ms/step - loss: 0.2404 - sparse_categorical_accuracy: 0.9338 Epoch 5/5 32/32 [==============================] - 0s 2ms/step - loss: 0.1419 - sparse_categorical_accuracy: 0.9679

Now, recreate the model from that file:

```
# Recreate the exact same model, including its weights and the optimizer
new_model = tf.keras.models.load_model('my_model.h5')
# Show the model architecture
new_model.summary()
```

Model: "sequential_6" _________________________________________________________________ Layer (type) Output Shape Param # ================================================================= dense_12 (Dense) (None, 512) 401920 _________________________________________________________________ dropout_6 (Dropout) (None, 512) 0 _________________________________________________________________ dense_13 (Dense) (None, 10) 5130 ================================================================= Total params: 407,050 Trainable params: 407,050 Non-trainable params: 0 _________________________________________________________________

Check its accuracy:

```
loss, acc = new_model.evaluate(test_images, test_labels, verbose=2)
print('Restored model, accuracy: {:5.2f}%'.format(100 * acc))
```

32/32 - 0s - loss: 0.4260 - sparse_categorical_accuracy: 0.8680 Restored model, accuracy: 86.80%

Keras saves models by inspecting their architectures. This technique saves everything:

- The weight values
- The model's architecture
- The model's training configuration (what you pass to the
`.compile()`

method) - The optimizer and its state, if any (this enables you to restart training where you left off)

Keras is not able to save the `v1.x`

optimizers (from `tf.compat.v1.train`

) since they aren't compatible with checkpoints. For v1.x optimizers, you need to re-compile the model after loading—losing the state of the optimizer.

### Saving custom objects

If you are using the SavedModel format, you can skip this section. The key difference between HDF5 and SavedModel is that HDF5 uses object configs to save the model architecture, while SavedModel saves the execution graph. Thus, SavedModels are able to save custom objects like subclassed models and custom layers without requiring the original code.

To save custom objects to HDF5, you must do the following:

- Define a
`get_config`

method in your object, and optionally a`from_config`

classmethod.`get_config(self)`

returns a JSON-serializable dictionary of parameters needed to recreate the object.`from_config(cls, config)`

uses the returned config from`get_config`

to create a new object. By default, this function will use the config as initialization kwargs (`return cls(**config)`

).

- Pass the object to the
`custom_objects`

argument when loading the model. The argument must be a dictionary mapping the string class name to the Python class. E.g.`tf.keras.models.load_model(path, custom_objects={'CustomLayer': CustomLayer})`

See the Writing layers and models from scratch tutorial for examples of custom objects and `get_config`

.

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