吴恩达深度学习课程第二课第三周（Tensorflow tutorial）作业

import h5py import numpy as np import tensorflow as tf import math def load_dataset(): train_dataset = h5py.File('datasets/train_signs.h5', "r") train_set_x_orig = np.array(train_dataset["train_set_x"][:]) # your train set features train_set_y_orig = np.array(train_dataset["train_set_y"][:]) # your train set labels test_dataset = h5py.File('datasets/test_signs.h5', "r") test_set_x_orig = np.array(test_dataset["test_set_x"][:]) # your test set features test_set_y_orig = np.array(test_dataset["test_set_y"][:]) # your test set labels classes = np.array(test_dataset["list_classes"][:]) # the list of classes train_set_y_orig = train_set_y_orig.reshape((1, train_set_y_orig.shape[0])) test_set_y_orig = test_set_y_orig.reshape((1, test_set_y_orig.shape[0])) return train_set_x_orig, train_set_y_orig, test_set_x_orig, test_set_y_orig, classes def random_mini_batches(X, Y, mini_batch_size = 64, seed = 0): """ Creates a list of random minibatches from (X, Y) Arguments: X -- input data, of shape (input size, number of examples) Y -- true "label" vector (containing 0 if cat, 1 if non-cat), of shape (1, number of examples) mini_batch_size - size of the mini-batches, integer seed -- this is only for the purpose of grading, so that you're "random minibatches are the same as ours. Returns: mini_batches -- list of synchronous (mini_batch_X, mini_batch_Y) """ m = X.shape[1] # number of training examples mini_batches = [] np.random.seed(seed) # Step 1: Shuffle (X, Y) permutation = list(np.random.permutation(m)) shuffled_X = X[:, permutation] shuffled_Y = Y[:, permutation].reshape((Y.shape[0],m)) # Step 2: Partition (shuffled_X, shuffled_Y). Minus the end case. num_complete_minibatches = math.floor(m/mini_batch_size) # number of mini batches of size mini_batch_size in your partitionning for k in range(0, num_complete_minibatches): mini_batch_X = shuffled_X[:, k * mini_batch_size : k * mini_batch_size + mini_batch_size] mini_batch_Y = shuffled_Y[:, k * mini_batch_size : k * mini_batch_size + mini_batch_size] mini_batch = (mini_batch_X, mini_batch_Y) mini_batches.append(mini_batch) # Handling the end case (last mini-batch < mini_batch_size) if m % mini_batch_size != 0: mini_batch_X = shuffled_X[:, num_complete_minibatches * mini_batch_size : m] mini_batch_Y = shuffled_Y[:, num_complete_minibatches * mini_batch_size : m] mini_batch = (mini_batch_X, mini_batch_Y) mini_batches.append(mini_batch) return mini_batches def convert_to_one_hot(Y, C): Y = np.eye(C)[Y.reshape(-1)].T return Y def predict(X, parameters): W1 = tf.convert_to_tensor(parameters["W1"]) b1 = tf.convert_to_tensor(parameters["b1"]) W2 = tf.convert_to_tensor(parameters["W2"]) b2 = tf.convert_to_tensor(parameters["b2"]) W3 = tf.convert_to_tensor(parameters["W3"]) b3 = tf.convert_to_tensor(parameters["b3"]) params = {"W1": W1, "b1": b1, "W2": W2, "b2": b2, "W3": W3, "b3": b3} x = tf.placeholder("float", [12288, 1]) z3 = forward_propagation(x, params) p = tf.argmax(z3) with tf.Session() as sess: prediction = sess.run(p, feed_dict = {x: X}) return prediction def create_placeholders(n_x, n_y): """ Creates the placeholders for the tensorflow session. Arguments: n_x -- scalar, size of an image vector (num_px * num_px = 64 * 64 * 3 = 12288) n_y -- scalar, number of classes (from 0 to 5, so -> 6) Returns: X -- placeholder for the data input, of shape [n_x, None] and dtype "float" Y -- placeholder for the input labels, of shape [n_y, None] and dtype "float" Tips: - You will use None because it let's us be flexible on the number of examples you will for the placeholders. In fact, the number of examples during test/train is different. """ ### START CODE HERE ### (approx. 2 lines) X = tf.placeholder("float", [n_x, None]) Y = tf.placeholder("float", [n_y, None]) ### END CODE HERE ### return X, Y def initialize_parameters(): """ Initializes parameters to build a neural network with tensorflow. The shapes are: W1 : [25, 12288] b1 : [25, 1] W2 : [12, 25] b2 : [12, 1] W3 : [6, 12] b3 : [6, 1] Returns: parameters -- a dictionary of tensors containing W1, b1, W2, b2, W3, b3 """ tf.set_random_seed(1) # so that your "random" numbers match ours ### START CODE HERE ### (approx. 6 lines of code) W1 = tf.get_variable("W1", [25,12288], initializer = tf.contrib.layers.xavier_initializer(seed = 1)) b1 = tf.get_variable("b1", [25,1], initializer = tf.zeros_initializer()) W2 = tf.get_variable("W2", [12,25], initializer = tf.contrib.layers.xavier_initializer(seed = 1)) b2 = tf.get_variable("b2", [12,1], initializer = tf.zeros_initializer()) W3 = tf.get_variable("W3", [6,12], initializer = tf.contrib.layers.xavier_initializer(seed = 1)) b3 = tf.get_variable("b3", [6,1], initializer = tf.zeros_initializer()) ### END CODE HERE ### parameters = {"W1": W1, "b1": b1, "W2": W2, "b2": b2, "W3": W3, "b3": b3} return parameters def compute_cost(z3, Y): """ Computes the cost Arguments: z3 -- output of forward propagation (output of the last LINEAR unit), of shape (10, number of examples) Y -- "true" labels vector placeholder, same shape as z3 Returns: cost - Tensor of the cost function """ # to fit the tensorflow requirement for tf.nn.softmax_cross_entropy_with_logits() logits = tf.transpose(z3) labels = tf.transpose(Y) ### START CODE HERE ### (1 line of code) cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits = logits, labels = labels)) ### END CODE HERE ### return cost def model(X_train, Y_train, X_test, Y_test, learning_rate = 0.0001, num_epochs = 1500, minibatch_size = 32, print_cost = True): """ Implements a three-layer tensorflow neural network: LINEAR->RELU->LINEAR->RELU->LINEAR->SOFTMAX. Arguments: X_train -- training set, of shape (input size = 12288, number of training examples = 1080) Y_train -- test set, of shape (output size = 6, number of training examples = 1080) X_test -- training set, of shape (input size = 12288, number of training examples = 120) Y_test -- test set, of shape (output size = 6, number of test examples = 120) learning_rate -- learning rate of the optimization num_epochs -- number of epochs of the optimization loop minibatch_size -- size of a minibatch print_cost -- True to print the cost every 100 epochs Returns: parameters -- parameters learnt by the model. They can then be used to predict. """ ops.reset_default_graph() # to be able to rerun the model without overwriting tf variables tf.set_random_seed(1) # to keep consistent results seed = 3 # to keep consistent results (n_x, m) = X_train.shape # (n_x: input size, m : number of examples in the train set) n_y = Y_train.shape[0] # n_y : output size costs = [] # To keep track of the cost # Create Placeholders of shape (n_x, n_y) ### START CODE HERE ### (1 line) X, Y = create_placeholders(n_x,