tf.experimental.tensorrt.Converter

An offline converter for TF-TRT transformation for TF 2.0 SavedModels.

tf.experimental.tensorrt.Converter(
    input_saved_model_dir=None,
    input_saved_model_tags=None,
    input_saved_model_signature_key=None,
    use_dynamic_shape=None,
    dynamic_shape_profile_strategy=None,
    max_workspace_size_bytes=DEFAULT_TRT_MAX_WORKSPACE_SIZE_BYTES,
    precision_mode=TrtPrecisionMode.FP32,
    minimum_segment_size=3,
    maximum_cached_engines=1,
    use_calibration=True,
    allow_build_at_runtime=True,
    conversion_params=None
)

Windows support is provided experimentally. No guarantee is made regarding functionality or engineering support. Use at your own risk.

There are several ways to run the conversion:

  1. FP32/FP16 precision

    params = tf.experimental.tensorrt.ConversionParams(
    precision_mode='FP16')
converter = tf.experimental.tensorrt.Converter(
    input_saved_model_dir="my_dir", conversion_params=params)
converter.convert()
converter.save(output_saved_model_dir)

    In this case, no TRT engines will be built or saved in the converted SavedModel. But if input data is available during conversion, we can still build and save the TRT engines to reduce the cost during inference (see option 2 below).

  2. FP32/FP16 precision with pre-built engines

    params = tf.experimental.tensorrt.ConversionParams(
    precision_mode='FP16',
    # Set this to a large enough number so it can cache all the engines.
    maximum_cached_engines=16)
converter = tf.experimental.tensorrt.Converter(
    input_saved_model_dir="my_dir", conversion_params=params)
converter.convert()

# Define a generator function that yields input data, and use it to execute
# the graph to build TRT engines.
def my_input_fn():
  for _ in range(num_runs):
    inp1, inp2 = ...
    yield inp1, inp2

converter.build(input_fn=my_input_fn)  # Generate corresponding TRT engines
converter.save(output_saved_model_dir)  # Generated engines will be saved.

    In this way, one engine will be built/saved for each unique input shapes of the TRTEngineOp. This is good for applications that cannot afford building engines during inference but have access to input data that is similar to the one used in production (for example, that has the same input shapes). Also, the generated TRT engines is platform dependent, so we need to run build() in an environment that is similar to production (e.g. with same type of GPU).

  3. INT8 precision and calibration with pre-built engines

    params = tf.experimental.tensorrt.ConversionParams(
    precision_mode='INT8',
    # Currently only one INT8 engine is supported in this mode.
    maximum_cached_engines=1,
    use_calibration=True)
converter = tf.experimental.tensorrt.Converter(
    input_saved_model_dir="my_dir", conversion_params=params)

# Define a generator function that yields input data, and run INT8
# calibration with the data. All input data should have the same shape.
# At the end of convert(), the calibration stats (e.g. range information)
# will be saved and can be used to generate more TRT engines with different
# shapes. Also, one TRT engine will be generated (with the same shape as
# the calibration data) for save later.
def my_calibration_input_fn():
  for _ in range(num_runs):
    inp1, inp2 = ...
    yield inp1, inp2

converter.convert(calibration_input_fn=my_calibration_input_fn)

# (Optional) Generate more TRT engines offline (same as the previous
# option), to avoid the cost of generating them during inference.
def my_input_fn():
  for _ in range(num_runs):
    inp1, inp2 = ...
    yield inp1, inp2
converter.build(input_fn=my_input_fn)

# Save the TRT engine and the engines.
converter.save(output_saved_model_dir)

  4. To use dynamic shape, we need to call the build method with an input function to generate profiles. This step is similar to the INT8 calibration step described above. The converter also needs to be created with use_dynamic_shape=True and one of the following profile_strategies for creating profiles based on the inputs produced by the input function:

    • Range: create one profile that works for inputs with dimension values in the range of [min_dims, max_dims] where min_dims and max_dims are derived from the provided inputs.
    • Optimal: create one profile for each input. The profile only works for inputs with the same dimensions as the input it is created for. The GPU engine will be run with optimal performance with such inputs.
    • Range+Optimal: create the profiles for both Range and Optimal.
    • ImplicitBatchModeCompatible: create the profiles that will produce the same GPU engines as the implicit_batch_mode would produce.

input_saved_model_dir the directory to load the SavedModel which contains the input graph to transforms. Required.
input_saved_model_tags list of tags to load the SavedModel.
input_saved_model_signature_key the key of the signature to optimize the graph for.
use_dynamic_shape whether to enable dynamic shape support. None is equivalent to False in the current implementation.
dynamic_shape_profile_strategy one of the strings in supported_profile_strategies(). None is equivalent to Range in the current implementation.
max_workspace_size_bytes the maximum GPU temporary memory that the TRT engine can use at execution time. This corresponds to the 'workspaceSize' parameter of nvinfer1::IBuilder::setMaxWorkspaceSize().
precision_mode one of the strings in TrtPrecisionMode.supported_precision_modes().
minimum_segment_size the minimum number of nodes required for a subgraph to be replaced by TRTEngineOp.
maximum_cached_engines max number of cached TRT engines for dynamic TRT ops. Created TRT engines for a dynamic dimension are cached. If the number of cached engines is already at max but none of them supports the input shapes, the TRTEngineOp will fall back to run the original TF subgraph that corresponds to the TRTEngineOp.
use_calibration this argument is ignored if precision_mode is not INT8. If set to True, a calibration graph will be created to calibrate the missing ranges. The calibration graph must be converted to an inference graph by running calibration with calibrate(). If set to False, quantization nodes will be expected for every tensor in the graph (excluding those which will be fused). If a range is missing, an error will occur. Please note that accuracy may be negatively affected if there is a mismatch between which tensors TRT quantizes and which tensors were trained with fake quantization.
allow_build_at_runtime whether to allow building TensorRT engines during runtime if no prebuilt TensorRT engine can be found that can handle the given inputs during runtime, then a new TensorRT engine is built at runtime if allow_build_at_runtime=True, and otherwise native TF is used.
conversion_params a TrtConversionParams instance (deprecated).

ValueError if the combination of the parameters is invalid.

Methods

build

View source

build(
    input_fn
)

Run inference with converted graph in order to build TensorRT engines.

Args
input_fn a generator function that yields input data as a list or tuple or dict, which will be used to execute the converted signature to generate TRT engines. Example: def input_fn(): # Let's assume a network with 2 input tensors. We generate 3 sets # of dummy input data: input_shapes = [[(1, 16), (2, 16)], # 1st input list [(2, 32), (4, 32)], # 2nd list of two tensors [(4, 32), (8, 32)]] # 3rd input list for shapes in input_shapes: # return a list of input tensors yield [np.zeros(x).astype(np.float32) for x in shapes]

Raises
NotImplementedError build() is already called.
RuntimeError the input_fx is None.

convert

View source

convert(
    calibration_input_fn=None
)

Convert the input SavedModel in 2.0 format.

Args
calibration_input_fn a generator function that yields input data as a list or tuple or dict, which will be used to execute the converted signature for calibration. All the returned input data should have the same shape. Example: def input_fn(): yield input1, input2, input3

Raises
ValueError if the input combination is invalid.

Returns
The TF-TRT converted Function.

save

View source

save(
    output_saved_model_dir, save_gpu_specific_engines=True
)

Save the converted SavedModel.

Args
output_saved_model_dir directory to saved the converted SavedModel.
save_gpu_specific_engines whether to save TRT engines that have been built. When True, all engines are saved and when False, the engines are not saved and will be rebuilt at inference time. By using save_gpu_specific_engines=False after doing INT8 calibration, inference can be done on different GPUs than the GPU that the model was calibrated and saved on.

summary

View source

summary(
    line_length=160, detailed=True, print_fn=None
)

This method describes the results of the conversion by TF-TRT.

It includes information such as the name of the engine, the number of nodes per engine, the input and output dtype, along with the input shape of each TRTEngineOp.

Args
line_length Default line length when printing on the console. Minimum 160 characters long.
detailed Whether or not to show the nodes inside each TRTEngineOp.
print_fn Print function to use. Defaults to print. It will be called on each line of the summary. You can set it to a custom function in order to capture the string summary.

Raises
RuntimeError if the graph is not converted.