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Conversión del modelo Jax para TFLite

Descripción general

Este CodeLab demuestra cómo crear un modelo para el reconocimiento MNIST usando Jax y cómo convertirlo a TensorFlow Lite. Este laboratorio de código también demostrará cómo optimizar el modelo TFLite convertido a Jax con cuantificación posterior al entrenamiento.

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Prerrequisitos

Se recomienda probar esta función con la compilación de pip nocturna de TensorFlow más reciente.

pip install tf-nightly --upgrade
pip install jax --upgrade
pip install jaxlib --upgrade

Preparación de datos

Descargue los datos de MNIST con el conjunto de datos y el preprocesamiento de Keras.

import numpy as np
import tensorflow as tf
import functools

import time
import itertools

import numpy.random as npr

import jax.numpy as jnp
from jax import jit, grad, random
from jax.experimental import optimizers
from jax.experimental import stax
def _one_hot(x, k, dtype=np.float32):
  """Create a one-hot encoding of x of size k."""
  return np.array(x[:, None] == np.arange(k), dtype)

(train_images, train_labels), (test_images, test_labels) = tf.keras.datasets.mnist.load_data()
train_images, test_images = train_images / 255.0, test_images / 255.0
train_images = train_images.astype(np.float32)
test_images = test_images.astype(np.float32)

train_labels = _one_hot(train_labels, 10)
test_labels = _one_hot(test_labels, 10)
Downloading data from https://storage.googleapis.com/tensorflow/tf-keras-datasets/mnist.npz
11493376/11490434 [==============================] - 0s 0us/step
11501568/11490434 [==============================] - 0s 0us/step

Construye el modelo MNIST con Jax

def loss(params, batch):
  inputs, targets = batch
  preds = predict(params, inputs)
  return -jnp.mean(jnp.sum(preds * targets, axis=1))

def accuracy(params, batch):
  inputs, targets = batch
  target_class = jnp.argmax(targets, axis=1)
  predicted_class = jnp.argmax(predict(params, inputs), axis=1)
  return jnp.mean(predicted_class == target_class)

init_random_params, predict = stax.serial(
    stax.Flatten,
    stax.Dense(1024), stax.Relu,
    stax.Dense(1024), stax.Relu,
    stax.Dense(10), stax.LogSoftmax)

rng = random.PRNGKey(0)
WARNING:absl:No GPU/TPU found, falling back to CPU. (Set TF_CPP_MIN_LOG_LEVEL=0 and rerun for more info.)

Entrenar y evaluar el modelo

step_size = 0.001
num_epochs = 10
batch_size = 128
momentum_mass = 0.9


num_train = train_images.shape[0]
num_complete_batches, leftover = divmod(num_train, batch_size)
num_batches = num_complete_batches + bool(leftover)

def data_stream():
  rng = npr.RandomState(0)
  while True:
    perm = rng.permutation(num_train)
    for i in range(num_batches):
      batch_idx = perm[i * batch_size:(i + 1) * batch_size]
      yield train_images[batch_idx], train_labels[batch_idx]
batches = data_stream()

opt_init, opt_update, get_params = optimizers.momentum(step_size, mass=momentum_mass)

@jit
def update(i, opt_state, batch):
  params = get_params(opt_state)
  return opt_update(i, grad(loss)(params, batch), opt_state)

_, init_params = init_random_params(rng, (-1, 28 * 28))
opt_state = opt_init(init_params)
itercount = itertools.count()

print("\nStarting training...")
for epoch in range(num_epochs):
  start_time = time.time()
  for _ in range(num_batches):
    opt_state = update(next(itercount), opt_state, next(batches))
  epoch_time = time.time() - start_time

  params = get_params(opt_state)
  train_acc = accuracy(params, (train_images, train_labels))
  test_acc = accuracy(params, (test_images, test_labels))
  print("Epoch {} in {:0.2f} sec".format(epoch, epoch_time))
  print("Training set accuracy {}".format(train_acc))
  print("Test set accuracy {}".format(test_acc))
Starting training...
Epoch 0 in 4.69 sec
Training set accuracy 0.8729000091552734
Test set accuracy 0.880299985408783
Epoch 1 in 3.83 sec
Training set accuracy 0.8983666896820068
Test set accuracy 0.9047999978065491
Epoch 2 in 3.81 sec
Training set accuracy 0.9102166891098022
Test set accuracy 0.9138000011444092
Epoch 3 in 3.85 sec
Training set accuracy 0.9172500371932983
Test set accuracy 0.9218999743461609
Epoch 4 in 3.79 sec
Training set accuracy 0.9224500060081482
Test set accuracy 0.9253999590873718
Epoch 5 in 3.72 sec
Training set accuracy 0.9272000193595886
Test set accuracy 0.930899977684021
Epoch 6 in 3.77 sec
Training set accuracy 0.9327666759490967
Test set accuracy 0.9334999918937683
Epoch 7 in 3.77 sec
Training set accuracy 0.9360166788101196
Test set accuracy 0.9370999932289124
Epoch 8 in 3.77 sec
Training set accuracy 0.9390000104904175
Test set accuracy 0.939300000667572
Epoch 9 in 3.73 sec
Training set accuracy 0.9425666928291321
Test set accuracy 0.9429999589920044

Convierta al modelo TFLite.

Tenga en cuenta aquí, nosotros

  1. Inline los parametros a la Jax predict func con functools.partial .
  2. Construir un jnp.zeros , este es un "marcador de posición" tensor de Jax utiliza para trazar el modelo.
  3. Llamada experimental_from_jax :> * La serving_func se envuelve en una lista. > * La entrada se asocia con un nombre dado y se pasa como una matriz envuelta en una lista.
serving_func = functools.partial(predict, params)
x_input = jnp.zeros((1, 28, 28))
converter = tf.lite.TFLiteConverter.experimental_from_jax(
    [serving_func], [[('input1', x_input)]])
tflite_model = converter.convert()
with open('jax_mnist.tflite', 'wb') as f:
  f.write(tflite_model)
2021-10-30 11:51:13.208329: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:363] Ignored output_format.
2021-10-30 11:51:13.208375: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:366] Ignored drop_control_dependency.
2021-10-30 11:51:13.208383: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:372] Ignored change_concat_input_ranges.

Verifique el modelo TFLite convertido

Compare los resultados del modelo convertido con el modelo Jax.

expected = serving_func(train_images[0:1])

# Run the model with TensorFlow Lite
interpreter = tf.lite.Interpreter(model_content=tflite_model)
interpreter.allocate_tensors()
input_details = interpreter.get_input_details()
output_details = interpreter.get_output_details()
interpreter.set_tensor(input_details[0]["index"], train_images[0:1, :, :])
interpreter.invoke()
result = interpreter.get_tensor(output_details[0]["index"])

# Assert if the result of TFLite model is consistent with the JAX model.
np.testing.assert_almost_equal(expected, result, 1e-5)

Optimizar el modelo

Vamos a proporcionar un representative_dataset hacer quantiztion posterior a la capacitación para optimizar el modelo.

def representative_dataset():
  for i in range(1000):
    x = train_images[i:i+1]
    yield [x]

converter = tf.lite.TFLiteConverter.experimental_from_jax(
    [serving_func], [[('x', x_input)]])
tflite_model = converter.convert()
converter.optimizations = [tf.lite.Optimize.DEFAULT]
converter.representative_dataset = representative_dataset
converter.target_spec.supported_ops = [tf.lite.OpsSet.TFLITE_BUILTINS_INT8]
tflite_quant_model = converter.convert()
with open('jax_mnist_quant.tflite', 'wb') as f:
  f.write(tflite_quant_model)
2021-10-30 11:51:14.202412: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:363] Ignored output_format.
2021-10-30 11:51:14.202455: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:366] Ignored drop_control_dependency.
2021-10-30 11:51:14.202461: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:372] Ignored change_concat_input_ranges.
2021-10-30 11:51:14.293677: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:363] Ignored output_format.
2021-10-30 11:51:14.293768: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:366] Ignored drop_control_dependency.
2021-10-30 11:51:14.293776: W tensorflow/compiler/mlir/lite/python/tf_tfl_flatbuffer_helpers.cc:372] Ignored change_concat_input_ranges.
fully_quantize: 0, inference_type: 6, input_inference_type: 0, output_inference_type: 0

Evaluar el modelo optimizado

expected = serving_func(train_images[0:1])

# Run the model with TensorFlow Lite
interpreter = tf.lite.Interpreter(model_content=tflite_quant_model)
interpreter.allocate_tensors()
input_details = interpreter.get_input_details()
output_details = interpreter.get_output_details()
interpreter.set_tensor(input_details[0]["index"], train_images[0:1, :, :])
interpreter.invoke()
result = interpreter.get_tensor(output_details[0]["index"])

# Assert if the result of TFLite model is consistent with the Jax model.
np.testing.assert_almost_equal(expected, result, 1e-5)

Compare el tamaño del modelo cuantificado

Deberíamos poder ver que el modelo cuantificado es cuatro veces más pequeño que el modelo original.

du -h jax_mnist.tflite
du -h jax_mnist_quant.tflite
7.2M    jax_mnist.tflite
1.8M    jax_mnist_quant.tflite