clear_session: Resets all state generated by Keras.

In keras3: R Interface to 'Keras'

Resets all state generated by Keras.

Description

Keras manages a global state, which it uses to implement the Functional model-building API and to uniquify autogenerated layer names.

If you are creating many models in a loop, this global state will consume an increasing amount of memory over time, and you may want to clear it. Calling clear_session() releases the global state: this helps avoid clutter from old models and layers, especially when memory is limited.

Example 1: calling clear_session() when creating models in a loop

for (i in 1:100) {
  # Without `clear_session()`, each iteration of this loop will
  # slightly increase the size of the global state managed by Keras
  model <- keras_model_sequential()
  for (j in 1:10) {
    model <- model |> layer_dense(units = 10)
  }
}

for (i in 1:100) {
  # With `clear_session()` called at the beginning,
  # Keras starts with a blank state at each iteration
  # and memory consumption is constant over time.
  clear_session()
  model <- keras_model_sequential()
  for (j in 1:10) {
    model <- model |> layer_dense(units = 10)
  }
}

Example 2: resetting the layer name generation counter

layers <- lapply(1:10, \(i) layer_dense(units = 10))

new_layer <- layer_dense(units = 10)
print(new_layer$name)

## [1] "dense_10"

clear_session()
new_layer <- layer_dense(units = 10)
print(new_layer$name)

## [1] "dense"

Usage

clear_session(free_memory = TRUE)

Arguments

free_memory

Whether to call Python garbage collection. It's usually a good practice to call it to make sure memory used by deleted objects is immediately freed. However, it may take a few seconds to execute, so when using clear_session() in a short loop, you may want to skip it.

Value

NULL, invisibly, called for side effects.

See Also

• https://keras.io/api/utils/config_utils#clearsession-function

Other backend:
config_backend()
config_epsilon()
config_floatx()
config_image_data_format()
config_set_epsilon()
config_set_floatx()
config_set_image_data_format()

Other utils:
audio_dataset_from_directory()
config_disable_interactive_logging()
config_disable_traceback_filtering()
config_enable_interactive_logging()
config_enable_traceback_filtering()
config_is_interactive_logging_enabled()
config_is_traceback_filtering_enabled()
get_file()
get_source_inputs()
image_array_save()
image_dataset_from_directory()
image_from_array()
image_load()
image_smart_resize()
image_to_array()
layer_feature_space()
normalize()
pad_sequences()
set_random_seed()
split_dataset()
text_dataset_from_directory()
timeseries_dataset_from_array()
to_categorical()
zip_lists()

keras3 documentation built on June 8, 2025, 1:36 p.m.