Please see https://github.com/tensorflow/tensorflow/blob/r2.9/RELEASE.md for Keras release notes.

Major Features and Improvements

• tf.keras:
  • Added tf.keras.applications.resnet_rs models. This includes the ResNetRS50, ResNetRS101, ResNetRS152, ResNetRS200, ResNetRS270, ResNetRS350 and ResNetRS420 model architectures. The ResNetRS models are based on the architecture described in Revisiting ResNets: Improved Training and Scaling Strategies
  • Added tf.keras.optimizers.experimental.Optimizer. The reworked optimizer gives more control over different phases of optimizer calls, and is easier to customize. We provide Adam, SGD, Adadelta, AdaGrad and RMSprop optimizers based on tf.keras.optimizers.experimental.Optimizer. Generally the new optimizers work in the same way as the old ones, but support new constructor arguments. In the future, the symbols tf.keras.optimizers.Optimizer/Adam/etc will point to the new optimizers, and the previous generation of optimizers will be moved to tf.keras.optimizers.legacy.Optimizer/Adam/etc.
  • Added L2 unit normalization layer tf.keras.layers.UnitNormalization.
  • Added tf.keras.regularizers.OrthogonalRegularizer, a new regularizer that encourages orthogonality between the rows (or columns) or a weight matrix.
  • Added tf.keras.layers.RandomBrightness layer for image preprocessing.
  • Added APIs for switching between interactive logging and absl logging. By default, Keras always writes the logs to stdout. However, this is not optimal in a non-interactive environment, where you don't have access to stdout, but can only view the logs. You can use tf.keras.utils.disable_interactive_logging() to write the logs to ABSL logging. You can also use tf.keras.utils.enable_interactive_logging() to change it back to stdout, or tf.keras.utils.is_interactive_logging_enabled() to check if interactive logging is enabled.
  • Changed default value for the verbose argument of Model.evaluate() and Model.predict() to "auto", which defaults to verbose=1 for most cases and defaults to verbose=2 when used with ParameterServerStrategy or with interactive logging disabled.
  • Argument jit_compile in Model.compile() now applies to Model.evaluate() and Model.predict(). Setting jit_compile=True in compile() compiles the model's training, evaluation, and inference steps to XLA. Note that jit_compile=True may not necessarily work for all models.
  • Added DTensor-related Keras APIs under tf.keras.dtensor namespace. The APIs are still classified as experimental. You are welcome to try it out. Please check the tutoral and guide on https://www.tensorflow.org/ for more details about DTensor.

What's Changed

• Update_OptimizerV2.py by @sachinprasadhs in #15819
• Use assign_sub when computing moving_average_update by @lgeiger in #15773
• Document the verbose parameter in EarlyStopping by @ThunderKey in #15817
• Fix LSTM and GRU cuDNN kernel failure for RaggedTensors. by @foxik in #15756
• A tiny problem in an AttributeError message in base_layer.py by @Aujkst in #15847
• Update training_generator_test.py by @sachinprasadhs in #15876
• Minor correction in RegNet docs by @AdityaKane2001 in #15901
• add scoring methods in Luong-style attention by @old-school-kid in #15867
• refactoring code with List Comprehension by @idiomaticrefactoring in #15924
• added clarifying statement to save_model example text by @soosung80 in #15930
• Update base_conv.py by @AdityaKane2001 in #15943
• Update global_clipnorm by @sachinprasadhs in #15938
• Update callbacks.py by @Cheril311 in #15977
• Applied correct reshaping to metric func sparse_top_k by @dfossl in #15997
• Keras saving/loading: Add a custom object saving test to verify the keras.utils.register_keras_serializable flows we are expecting users to follow work, and will continue to work with the new design and implementation coming in. by @copybara-service in #15992
• Metric accuracy bug fixes - Metrics Refactor proposal by @dfossl in #16010
• Make classifier_activation argument accessible for DenseNet and NASNet models by @adrhill in #16005
• Copy image utils from keras_preprocessing directly into core keras by @copybara-service in #15975
• Update keras.callbacks.BackupAndRestore docs by @lgeiger in #16018
• Updating the definition of an argument in the text_dataset_from_directory function by @shraddhazpy in #16012
• Remove deprecated TF1 Layer APIs apply(), get_updates_for(), get_losses_for(), and remove the inputs argument in the add_loss() method. by @copybara-service in #16046
• Fixed minor typos by @hdubbs in #16071
• Fix typo in documentation by @futtetennista in #16082
• Issue #16090: Split input_shapes horizontally in utils.vis_utils.plot_model by @RicardFos in #16096
• Docker env setup related changes by @shraddhazpy in #16040
• Fixed EfficientNetV2 b parameter not increasing with each block. by @sebastian-sz in #16145
• Updated args of train_on_batch method by @jvishnuvardhan in #16147
• Binary accuracy bug fixes - Metric accuracy method refactor by @dfossl in #16083
• Fix the corner case for dtensor model layout map. by @copybara-service in #16170
• Fix typo in docstring for DenseFeatures by @gadagashwini in #16165
• Fix typo in Returns Section by @chunduriv in #16182
• Some tests misusing assertTrue for comparisons fix by @code-review-doctor in #16073
• Add .DS_Store to .gitignore for macOS users by @tsheaff in #16198
• Solve memory inefficiency in RNNs by @atmguille in #16174
• Update README.md by @ahmedopolis in #16259
• Fix documentation text being mistakenly rendered as code by @guberti in #16253
• Allow single input for merging layers Add, Average, Concatenate, Maximum, Minimum, Multiply by @foxik in #16230
• Mention image dimensions format in image_dataset_from_directory by @nrzimmermann in #16232
• fix thresholded_relu to support list datatype by @old-school-kid in #16277
• Implement all tf interpolation upscaling methods by @Mahrkeenerh in #16249

New Contributors

• @lgeiger made their first contribution in #15773
• @ThunderKey made their first contribution in #15817
• @Aujkst made their first contribution in #15847
• @idiomaticrefactoring made their first contribution in #15924
• @soosung80 made their first contribution in #15930
• @Cheril311 made their first contribution in #15977
• @dfossl made their first contribution in #15997
• @adrhill made their first contribution in #16005
• @shraddhazpy made their first contribution in #16012
• @hdubbs made their first contribution in #16071
• @futtetennista made their first contribution in #16082
• @RicardFos made their first contribution in #16096
• @gadagashwini made their first contribution in #16165
• @chunduriv made their first contribution in #16182
• @code-review-doctor made their first contribution in #16073
• @tsheaff made their first contribution in #16198
• @atmguille made their first contribution in #16174
• @ahmedopolis made their first contribution in #16259
• @guberti made their first contribution in #16253
• @nrzimmermann made their first contribution in #16232
• @Mahrkeenerh made their first contribution in #16249

Full Changelog: v2.8.0-rc0...v2.9.0-rc0