clone_model {keras3}

Clone a Functional or Sequential Model instance.

Description

Model cloning is similar to calling a model on new inputs, except that it creates new layers (and thus new weights) instead of sharing the weights of the existing layers.

Note that clone_model() will not preserve the uniqueness of shared objects within the model (e.g. a single variable attached to two distinct layers will be restored as two separate variables).

Usage

clone_model(
  model,
  input_tensors = NULL,
  clone_function = NULL,
  call_function = NULL,
  recursive = FALSE,
  ...
)

Arguments

model

Instance of Model (could be a Functional model or a Sequential model).

input_tensors

Optional list of input tensors to build the model upon. If not provided, new keras_input() objects will be created.

clone_function

Callable with signature ⁠function(layer)⁠ to be used to clone each layer in the target model (except Input instances). It takes as argument the layer instance to be cloned, and returns the corresponding layer instance to be used in the model copy. If unspecified, this callable defaults to the following serialization/deserialization function: function(layer) layer$`__class__`$from_config(layer$get_config()). By passing a custom callable, you can customize your copy of the model, e.g. by wrapping certain layers of interest (you might want to replace all LSTM instances with equivalent Bidirectional(LSTM(...)) instances, for example). Defaults to NULL.

call_function

Callable with signature ⁠function(layer, ...)⁠ to be used to call each cloned layer and a set of inputs. It takes the layer instance, and the call arguments, and returns the call outputs. If unspecified, this callable defaults to the regular call() method: function(layer, ...) do.call(layer, list(...)). By passing a custom callable, you can insert new layers before or after a given layer.

recursive

Note, This argument can only be used with Functional models. Boolean. Whether to recursively clone any Sequential or Functional models encountered in the original Sequential/Functional model. If FALSE, then inner models are cloned by calling clone_function(). If TRUE, then inner models are cloned by calling clone_model() with the same clone_function, call_function, and recursive arguments. Note that in this case, call_function will not be propagated to any Sequential model (since it is not applicable to Sequential models).

...

For forward/backward compatability.

Value

An instance of Model reproducing the behavior of the original model, on top of new inputs tensors, using newly instantiated weights. The cloned model may behave differently from the original model if a custom clone_function or call_function modifies a layer or layer call.

Examples

# Create a test Sequential model.
model <- keras_model_sequential(input_shape = c(728)) |>
  layer_dense(32, activation = 'relu') |>
  layer_dense(1, activation = 'sigmoid')

# Create a copy of the test model (with freshly initialized weights).
new_model <- clone_model(model)

Using a clone_function to make a model deterministic by setting the random seed everywhere:

clone_function <- function(layer) {
  config <- layer$get_config()
  if ("seed" %in% names(config))
    config$seed <- 1337L
  layer$`__class__`$from_config(config)
}

new_model <- clone_model(model, clone_function = clone_function)

Using a call_function to add a Dropout layer after each Dense layer (without recreating new layers):

call_function <- function(layer, ...) {
  out <- layer(...)
  if (inherits(layer, keras$layers$Dense))
    out <- out |> layer_dropout(0.5)
  out
}

inputs <- keras_input(c(728))
outputs <- inputs |>
  layer_dense(32, activation = 'relu') |>
  layer_dense(1, activation = 'sigmoid')
model <- keras_model(inputs, outputs)

new_model <- clone_model(
  model,
  clone_function = function(x) x, # Reuse the same layers.
  call_function = call_function,
)
new_model

## Model: "functional_4"
## +-----------------------------------+--------------------------+---------------+
## | Layer (type)                      | Output Shape             |       Param # |
## +===================================+==========================+===============+
## | keras_tensor_8 (InputLayer)       | (None, 728)              |             0 |
## +-----------------------------------+--------------------------+---------------+
## | dense_2 (Dense)                   | (None, 32)               |        23,328 |
## +-----------------------------------+--------------------------+---------------+
## | dropout (Dropout)                 | (None, 32)               |             0 |
## +-----------------------------------+--------------------------+---------------+
## | dense_3 (Dense)                   | (None, 1)                |            33 |
## +-----------------------------------+--------------------------+---------------+
## | dropout_1 (Dropout)               | (None, 1)                |             0 |
## +-----------------------------------+--------------------------+---------------+
##  Total params: 23,361 (91.25 KB)
##  Trainable params: 23,361 (91.25 KB)
##  Non-trainable params: 0 (0.00 B)

Note that subclassed models cannot be cloned by default, since their internal layer structure is not known. To achieve equivalent functionality as clone_model in the case of a subclassed model, simply make sure that the model class implements get_config() (and optionally from_config()), and call:

new_model <- model$`__class__`$from_config(model$get_config())

In the case of a subclassed model, you cannot using a custom clone_function.