forked from 626_privacy/tensorflow_privacy
184 lines
7.2 KiB
Python
184 lines
7.2 KiB
Python
# Copyright 2018, The TensorFlow Authors.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Training a CNN on MNIST with differentially private SGD optimizer."""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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import numpy as np
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import tensorflow as tf
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from privacy.analysis.rdp_accountant import compute_rdp
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from privacy.analysis.rdp_accountant import get_privacy_spent
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from privacy.optimizers import dp_optimizer
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tf.flags.DEFINE_boolean('dpsgd', True, 'If True, train with DP-SGD. If False,'
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'train with vanilla SGD.')
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tf.flags.DEFINE_float('learning_rate', 0.08, 'Learning rate for training')
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tf.flags.DEFINE_float('noise_multiplier', 1.12,
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'Ratio of the standard deviation to the clipping norm')
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tf.flags.DEFINE_float('l2_norm_clip', 1.0, 'Clipping norm')
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tf.flags.DEFINE_integer('batch_size', 256, 'Batch size')
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tf.flags.DEFINE_integer('epochs', 60, 'Number of epochs')
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tf.flags.DEFINE_integer('microbatches', 256,
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'Number of microbatches (must evenly divide batch_size')
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tf.flags.DEFINE_string('model_dir', None, 'Model directory')
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FLAGS = tf.flags.FLAGS
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def cnn_model_fn(features, labels, mode):
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"""Model function for a CNN."""
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# Define CNN architecture using tf.keras.layers.
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input_layer = tf.reshape(features['x'], [-1, 28, 28, 1])
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y = tf.keras.layers.Conv2D(16, 8,
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strides=2,
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padding='same',
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kernel_initializer='he_normal').apply(input_layer)
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y = tf.keras.layers.MaxPool2D(2, 1).apply(y)
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y = tf.keras.layers.Conv2D(32, 4,
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strides=2,
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padding='valid',
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kernel_initializer='he_normal').apply(y)
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y = tf.keras.layers.MaxPool2D(2, 1).apply(y)
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y = tf.keras.layers.Flatten().apply(y)
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y = tf.keras.layers.Dense(32, kernel_initializer='he_normal').apply(y)
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logits = tf.keras.layers.Dense(10, kernel_initializer='he_normal').apply(y)
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# Calculate loss as a vector (to support microbatches in DP-SGD).
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vector_loss = tf.nn.softmax_cross_entropy_with_logits_v2(
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labels=labels, logits=logits)
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# Define mean of loss across minibatch (for reporting through tf.Estimator).
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scalar_loss = tf.reduce_mean(vector_loss)
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# Configure the training op (for TRAIN mode).
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if mode == tf.estimator.ModeKeys.TRAIN:
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if FLAGS.dpsgd:
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# Use DP version of GradientDescentOptimizer. For illustration purposes,
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# we do that here by calling make_optimizer_class() explicitly, though DP
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# versions of standard optimizers are available in dp_optimizer.
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dp_optimizer_class = dp_optimizer.make_optimizer_class(
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tf.train.GradientDescentOptimizer)
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optimizer = dp_optimizer_class(
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learning_rate=FLAGS.learning_rate,
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noise_multiplier=FLAGS.noise_multiplier,
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l2_norm_clip=FLAGS.l2_norm_clip,
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num_microbatches=FLAGS.microbatches)
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else:
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optimizer = tf.train.GradientDescentOptimizer(
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learning_rate=FLAGS.learning_rate)
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global_step = tf.train.get_global_step()
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train_op = optimizer.minimize(loss=vector_loss, global_step=global_step)
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return tf.estimator.EstimatorSpec(mode=mode,
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loss=scalar_loss,
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train_op=train_op)
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# Add evaluation metrics (for EVAL mode).
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elif mode == tf.estimator.ModeKeys.EVAL:
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eval_metric_ops = {
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'accuracy':
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tf.metrics.accuracy(
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labels=tf.argmax(labels, axis=1),
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predictions=tf.argmax(input=logits, axis=1))
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}
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return tf.estimator.EstimatorSpec(mode=mode,
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loss=scalar_loss,
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eval_metric_ops=eval_metric_ops)
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def load_mnist():
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"""Loads MNIST and preprocesses to combine training and validation data."""
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train, test = tf.keras.datasets.mnist.load_data()
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train_data, train_labels = train
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test_data, test_labels = test
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train_data = np.array(train_data, dtype=np.float32) / 255
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test_data = np.array(test_data, dtype=np.float32) / 255
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train_labels = tf.keras.utils.to_categorical(train_labels)
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test_labels = tf.keras.utils.to_categorical(test_labels)
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assert train_data.min() == 0.
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assert train_data.max() == 1.
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assert test_data.min() == 0.
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assert test_data.max() == 1.
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assert train_labels.shape[1] == 10
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assert test_labels.shape[1] == 10
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return train_data, train_labels, test_data, test_labels
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def main(unused_argv):
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tf.logging.set_verbosity(tf.logging.INFO)
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if FLAGS.batch_size % FLAGS.microbatches != 0:
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raise ValueError('Number of microbatches should divide evenly batch_size')
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# Load training and test data.
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train_data, train_labels, test_data, test_labels = load_mnist()
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# Instantiate the tf.Estimator.
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mnist_classifier = tf.estimator.Estimator(model_fn=cnn_model_fn,
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model_dir=FLAGS.model_dir)
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# Create tf.Estimator input functions for the training and test data.
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train_input_fn = tf.estimator.inputs.numpy_input_fn(
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x={'x': train_data},
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y=train_labels,
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batch_size=FLAGS.batch_size,
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num_epochs=FLAGS.epochs,
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shuffle=True)
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eval_input_fn = tf.estimator.inputs.numpy_input_fn(
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x={'x': test_data},
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y=test_labels,
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num_epochs=1,
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shuffle=False)
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# Define a function that computes privacy budget expended so far.
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def compute_epsilon(steps):
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"""Computes epsilon value for given hyperparameters."""
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if FLAGS.noise_multiplier == 0.0:
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return float('inf')
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orders = [1 + x / 10. for x in range(1, 100)] + list(range(12, 64))
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sampling_probability = FLAGS.batch_size / 60000
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rdp = compute_rdp(q=sampling_probability,
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noise_multiplier=FLAGS.noise_multiplier,
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steps=steps,
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orders=orders)
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# Delta is set to 1e-5 because MNIST has 60000 training points.
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return get_privacy_spent(orders, rdp, target_delta=1e-5)[0]
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# Training loop.
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steps_per_epoch = 60000 // FLAGS.batch_size
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for epoch in range(1, FLAGS.epochs + 1):
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# Train the model for one epoch.
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mnist_classifier.train(input_fn=train_input_fn, steps=steps_per_epoch)
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# Evaluate the model and print results
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eval_results = mnist_classifier.evaluate(input_fn=eval_input_fn)
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test_accuracy = eval_results['accuracy']
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print('Test accuracy after %d epochs is: %.3f' % (epoch, test_accuracy))
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# Compute the privacy budget expended so far.
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if FLAGS.dpsgd:
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eps = compute_epsilon(epoch * steps_per_epoch)
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print('For delta=1e-5, the current epsilon is: %.2f' % eps)
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else:
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print('Trained with vanilla non-private SGD optimizer')
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if __name__ == '__main__':
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tf.app.run()
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