In [2]:
import tensorflow as tf
print(tf.__version__)
In [3]:
h = tf.constant("Hello")
w = tf.constant("Machine Learning!")
hw = h + w
print(hw)
with tf.Session() as sess:
ans = sess.run(hw)
print(ans)
In [4]:
import tensorflow as tf
import numpy as np
# 使用 NumPy 生成假数据(phony data), 总共 100 个点.
x_data = np.float32(np.random.rand(2, 100)) # 随机输入
y_data = np.dot([0.100, 0.200], x_data) + 0.300
# 构造一个线性模型
#
b = tf.Variable(tf.zeros([1]))
W = tf.Variable(tf.zeros([1,2]))
y = tf.matmul(W, x_data) + b
# 最小化方差
loss = tf.reduce_mean(tf.square(y - y_data))
optimizer = tf.train.GradientDescentOptimizer(0.5)
train = optimizer.minimize(loss)
# 初始化变量
init = tf.global_variables_initializer()
# 启动图 (graph)
sess = tf.Session()
sess.run(init)
# 拟合平面
for step in range(0, 201):
sess.run(train)
if step % 20 == 0:
print (step, sess.run(W), sess.run(b))
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#理解MNIST数据集
import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data
import struct
import numpy as np
import matplotlib.pyplot as plt
def read_file():
with open("..//mnist//train-images-idx3-ubyte","rb") as f:
train_image = f.read()
with open('..//mnist//train-labels-idx1-ubyte', 'rb') as f:
train_label = f.read()
return train_image,train_label
train_image,train_label = read_file()
#因为数据结构中前4行的数据类型都是32位整型，所以采用i格式，但我们需要读取前4行数据，所以需要4个i。我们后面会看到标签集中，只使用2个ii。
fmt_header = '>IIII'
offset = 0
magic_number, num_images, num_rows, num_cols = struct.unpack_from(fmt_header, train_image, offset)
print('魔数:%d, 图片数量: %d张, 图片大小: %d*%d' % (magic_number, num_images, num_rows, num_cols))
offset_img = struct.calcsize(fmt_header)
offset_label = struct.calcsize(">II")
print(offset_img)
for i in range(10):#输出前十张图片和它们的标签
temp = struct.unpack_from(">784B",train_image,offset_img)
labels = struct.unpack_from(">B",train_label,offset_label)
img = np.reshape(temp,(28,28))
plt.imshow(img,cmap="Greys")
offset_img += 28*28
offset_label += struct.calcsize(">B")
print(labels[0])
plt.show()
for j in range(100):#输出前100个数字中 标签为7的所有数据
labels = struct.unpack_from(">B",train_label,offset_label)
if labels[0] == 7:
temp = struct.unpack_from(">784B",train_image,offset_img)
img = np.reshape(temp,(28,28))
plt.imshow(img,cmap="gray")
plt.show()
offset_img += 28*28
offset_label += struct.calcsize(">B")
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""" Neural Network.
A 2-Hidden Layers Fully Connected Neural Network (a.k.a Multilayer Perceptron)
implementation with TensorFlow. This example is using the MNIST database
of handwritten digits (http://yann.lecun.com/exdb/mnist/).
Links:
[MNIST Dataset](http://yann.lecun.com/exdb/mnist/).
Author: Aymeric Damien
Project: https://github.com/aymericdamien/TensorFlow-Examples/
"""
from __future__ import print_function
# Import MNIST data
from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets("..//mnist//", one_hot=True)
import tensorflow as tf
# Parameters
learning_rate = 0.1
num_steps = 500
batch_size = 128
display_step = 100
# Network Parameters
n_hidden_1 = 256 # 1st layer number of neurons
n_hidden_2 = 256 # 2nd layer number of neurons
num_input = 784 # MNIST data input (img shape: 28*28)
num_classes = 10 # MNIST total classes (0-9 digits)
# tf Graph input
X = tf.placeholder("float", [None, num_input])
Y = tf.placeholder("float", [None, num_classes])
# Store layers weight & bias
weights = {
'h1': tf.Variable(tf.random_normal([num_input, n_hidden_1])),
'h2': tf.Variable(tf.random_normal([n_hidden_1, n_hidden_2])),
'out': tf.Variable(tf.random_normal([n_hidden_2, num_classes]))
}
biases = {
'b1': tf.Variable(tf.random_normal([n_hidden_1])),
'b2': tf.Variable(tf.random_normal([n_hidden_2])),
'out': tf.Variable(tf.random_normal([num_classes]))
}
# Create model
def neural_net(x):
# Hidden fully connected layer with 256 neurons
layer_1 = tf.add(tf.matmul(x, weights['h1']), biases['b1'])
# Hidden fully connected layer with 256 neurons
layer_2 = tf.add(tf.matmul(layer_1, weights['h2']), biases['b2'])
# Output fully connected layer with a neuron for each class
out_layer = tf.matmul(layer_2, weights['out']) + biases['out']
return out_layer
# Construct model
logits = neural_net(X)
prediction = tf.nn.softmax(logits)
# Define loss and optimizer
loss_op = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(
logits=logits, labels=Y))
optimizer = tf.train.AdamOptimizer(learning_rate=learning_rate)
train_op = optimizer.minimize(loss_op)
# Evaluate model
correct_pred = tf.equal(tf.argmax(prediction, 1), tf.argmax(Y, 1))
accuracy = tf.reduce_mean(tf.cast(correct_pred, tf.float32))
# Initialize the variables (i.e. assign their default value)
init = tf.global_variables_initializer()
# Start training
with tf.Session() as sess:
# Run the initializer
sess.run(init)
for step in range(1, num_steps+1):
batch_x, batch_y = mnist.train.next_batch(batch_size)
# Run optimization op (backprop)
sess.run(train_op, feed_dict={X: batch_x, Y: batch_y})
if step % display_step == 0 or step == 1:
# Calculate batch loss and accuracy
loss, acc = sess.run([loss_op, accuracy], feed_dict={X: batch_x,
Y: batch_y})
print("Step " + str(step) + ", Minibatch Loss= " + \
"{:.4f}".format(loss) + ", Training Accuracy= " + \
"{:.3f}".format(acc))
print("Optimization Finished!")
# Calculate accuracy for MNIST test images
print("Testing Accuracy:", \
sess.run(accuracy, feed_dict={X: mnist.test.images,
Y: mnist.test.labels}))
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