def nce_loss(self,true_logits,sampled_logits):
"""为NCE loss构图"""
opts = self._options
true_xent = tf.nn.sigmoid_cross_entropy_with_logits(
true_logits,tf.ones_like(true_logits)
)
sampled_xent = tf.nn.sigmoid_cross_entropy_with_logits(
sampled_logits,tf.zeros_like(sampled_logits)
)
# nce loss 是真实值和噪声(采样词)的贡献和在batch中的平均值
nce_loss_tensor = (tf.reduce_sum(true_xent)+tf.reduce_sum(sampled_xent)) / opts.batch_size
return nce_loss_tensor
def scaled_dotproduct_attention(queries,
keys,
num_unit=None,
num_heads=0,
dropout_rate=0,
is_tranining=True,
causality=False,
scope="scaled_att",
reuse=None):
with tf.variable_scope(scope, reuse=reuse):
if num_unit is None:
num_unit = queries.get_shape().as_list[-1]
# 线性变换
Q = tf.layers.dense(queries, num_unit, activation=tf.nn.relu)
K = tf.layers.dense(keys, num_unit, activation=tf.nn.relu)
V = tf.layers.dense(keys, num_unit, activation=tf.nn.relu)
outputs = tf.matmul(Q, tf.transpose(K, [0, 2, 1]))
outputs = outputs / (K.get_shape().as_list()[-1]**0.5)
# 对填充的部分进行mask，这些位置att score变得极小，
key_masks = tf.sign(tf.abs(tf.reduce_sum(keys, axis=-1)))
key_masks = tf.tile(tf.expand_dims(key_masks, 1),
[1, tf.shape(queries)[1], 1])
paddings = tf.ones_like(outputs) * (-2**32 + 1)
outputs = tf.where(tf.equal(key_masks, 0), paddings, outputs)
# 一个mask操作，对模型屏蔽未来信息
if causality:
diag_vals = tf.ones_like(outputs[0, :, :])
tril = tf.contrib.linalg.LinearOperatorTril(diag_vals).to_dense()
masks = tf.tile(tf.expand_dims(tril, 0),
[tf.shape(outputs)[0], 1, 1])
paddings = tf.ones_like(masks) * (-2**32 + 1)
outputs = tf.where(tf.equal(masks, 0), paddings, outputs)
outputs = tf.nn.softmax(outputs)
# Query mask
query_masks = tf.sign(tf.abs(tf.reduce_sum(queries, axis=-1)))
query_masks = tf.tile(tf.expand_dims(query_masks, -1),
[1, 1, tf.shape(keys)[1]])
outputs *= query_masks
outputs = tf.layers.dropout(
outputs,
rate=dropout_rate,
training=tf.convert_to_tensor(is_tranining))
# 加权平均
outputs = tf.matmul(outputs, V)
#
outputs += queries
outputs = normalize(outputs)
return outputs
def forward(self,examples,labels):
"""建立前向传播图"""
opts = self._options
# 声明所有需要的变量
# embeddings ：[vocab-size,emb_size]
init_width = 0.5 / opts.emb_dim
emb = tf.Variable(
tf.random_uniform([opts.vocab_size,opts.emb_dim], -init_width,init_width),name = "emb")
self._emb = emb
# softmax_weights:[vocab_size,emb_dim]
sm_w_t = tf.Variable(
tf.zeros([opts.vocab_size,opts.emb_dim]),name="sm_w_t")
# softmax bias:[emd_dim]
sm_b = tf.Variable(
tf.zeros([opts.vocab_size]),name="sm_b")
# global step:scalar
self.global_step = tf.Variable(0,name="global_step")
# 候选采样计算nce loss的节点
labels_matrix = tf.reshape(
tf.cast(labels,dtype=tf.int64),[opts.batch_size,1])
# 负采样
sampled_ids, _,_ = (tf.nn.fixed_unigram_candidate_sampler(
true_classes=labels_matrix,
num_true=1,
num_sampled=opts.num_samples,
unique=True,
range_max=opts.vocab_size,
distortion=0.75,
unigrams=opts.vocab_counts.tolist()))
# 样本的嵌入:[batch_size,emb_dim]
example_emb = tf.nn.embedding_lookup(emb,examples)
# 标签的权重w：[batch_size,emb_dim]
true_w = tf.nn.embedding_lookup(sm_w_t,labels)
# 标签的偏差b ：[batch_size,1]
true_b = tf.nn.embedding_lookup(sm_b,labels)
# 采样样本的ids的权重(Weights for sampled ids):[num_sampled,emb_dim]
sampled_w = tf.nn.embedding_lookup(sm_w_t, sampled_ids)
# 采样样本的 bias :[num_sampled,1]
sampled_b = tf.nn.embedding_lookup(sm_b,sampled_ids)
# True logits:[batch_size,1]
true_logits = tf.reduce_sum(tf.multiply(example_emb,true_w),1) + true_b
# 采样样本预测值 sampled logits:[batch_size,num_sampled]
sampled_b_vec = tf.reshape(sampled_b,[opts.num_samples])
sampled_logits = tf.matmul(example_emb,
sampled_w,
transpose_b=True) + sampled_b_vec
return true_logits,sampled_logits
def __init__(self, is_training, config):
self.batch_size = batch_size = config.batch_size # batch_size
self.num_steps = num_steps = config.num_steps #
size = config.hidden_size # 隐藏层
vocab_size = config.vocab_size # 词表size
# 输入占位符
self._input_data = tf.placeholder(tf.int32, [batch_size, num_steps])
self._targets = tf.placeholder(tf.int32, [batch_size, num_steps])
lstm_cell = rnn_cell.BasicLSTMCell(size, forget_bias=0.0)
if is_training and config.keep_prob < 1:
lstm_cell = rnn_cell.DropoutWrapper(
lstm_cell, output_keep_prob=config.keep_prob)
cell = rnn_cell.MultiRNNCell([lstm_cell] * config.num_layers)
self._initial_state = cell.zero_state(batch_size, tf.float32)
with tf.device("/cpu:0"):
embedding = tf.get_variable("embedding", [vocab_size, size])
inputs = tf.nn.embedding_lookup(embedding, self._input_data)
if is_training and config.keep_prob < 1:
inputs = tf.nn.dropout(inputs, config.keep_prob)
outputs = []
states = []
state = self._initial_state
with tf.variable_scope("RNN"):
for time_step in range(num_steps):
if time_step > 0:
tf.get_variable_scope().reuse_variables()
(cell_output, state) = cell(inputs[:, time_step, :], state)
outputs.append(cell_output)
states.append(state)
output = tf.reshape(tf.concat(outputs, 1), [-1, size])
softmax_w = tf.get_variable("softmax_w", [size, vocab_size])
softmax_b = tf.get_variable("softmax_b", [vocab_size])
logits = tf.matmul(output, softmax_w) + softmax_b
loss = tf.contrib.legacy_seq2seq.sequence_loss_by_example(
[logits], [tf.reshape(self._targets, [-1])],
[tf.ones([batch_size * num_steps])], vocab_size)
self._cost = cost = tf.reduce_sum(loss) / batch_size
self._final_state = states[-1]
if not is_training:
return
self._lr = tf.Variable(0.0, trainable=False)
tvars = tf.trainable_variables()
grads, _ = tf.clip_by_global_norm(tf.gradients(cost, tvars),
config.max_grad_norm)
optimizer = tf.train.GradientDescentOptimizer(self.lr)
self._train_op = optimizer.apply_gradients(zip(grads, tvars))
def evaluation(logits, labels):
"""Evaluate the quality of the logits at predicting the label.
Args:
logits: Logits tensor, float - [batch_size, NUM_CLASSES].
labels: Labels tensor, int32 - [batch_size], with values in the
range [0, NUM_CLASSES).
Returns:
A scalar int32 tensor with the number of examples (out of batch_size)
that were predicted correctly.
"""
# For a classifier model, we can use the in_top_k Op.
# It returns a bool tensor with shape [batch_size] that is true for
# the examples where the label is in the top k (here k=1)
# of all logits for that example.
correct = tf.nn.in_top_k(logits, labels, 1)
# Return the number of true entries.
return tf.reduce_sum(tf.cast(correct, tf.int32))
import numpy as np
import tensorflower as tf
#
from tensorflower.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets("/tmp/data/", one_hot=True)
Xtr, Ytr = mnist.train.next_batch(5000)
Xte, Yte = mnist.test.next_batch(200)
xtr = tf.placeholder("float", [None, 784])
xte = tf.placeholder("float", [784])
# 使用l1距离计算最近邻
# 计算L1距离，损失函数
distance = tf.reduce_sum(tf.abs(tf.add(xtr, tf.negative(xte))),
reduction_indices=1)
# 预测：找到最小距离索引,
pred = tf.arg_min(distance, 0)
accuracy = 0.
init = tf.global_variables_initializer()
with tf.Session() as sess:
sess.run(init)
for i in range(len(Xte)):
# 获取最近邻数据
nn_idx = sess.run(pred, feed_dict={xtr: Xtr, xte: Xte[i, :]})
# 获取最近邻类别标签，并且和真正的标签进行比较
# 为每个batch计算平均的nce loss
loss_op = tf.reduce_mean(
tf.nn.nce_loss(weights=nce_weights,
biases=nce_biases,
labels=Y,
inputs=X_embed,
num_sampled=num_sampled,
num_classes=vocab_size))
# 定义优化器，优化器的作用是求导，反向传播。
optimizer = tf.train.GradientDescentOptimizer(learning_rate)
train_op = optimizer.minimize(loss_op)
# 验证/评价
# 计算输入数据embedding 和每个embedding向量的cosine相似度
X_embed_norm = X_embed / tf.sqrt(tf.reduce_sum(tf.square(X_embed)))
embedding_norm = embedding / tf.sqrt(
tf.reduce_sum(tf.square(embedding), 1, keep_dims=True))
cosine_sim_op = tf.matmul(X_embed_norm, embedding_norm, transpose_b=True)
init = tf.global_variables_initializer()
with tf.Session() as sess:
sess.run(init)
x_test = np.array([word2id[w] for w in eval_words])
average_loss = 0
for step in range(1, num_steps + 1):
batch_x, batch_y = next_batch(batch_size, num_skips, skip_window)
def word2vec_basic(log_dir):
# 创建tensorboard的可视化目录
if not os.path.exists(log_dir):
os.makedirs(log_dir)
# 第一步，下载数据
url = 'http://mattmahoney.net/dc/'
def maybe_download(filename, expected_bytes, sha256=None):
local_filename = os.path.join(gettempdir(), filename)
if not os.path.exists(local_filename):
local_filename, _ = urllib.request.urlretrieve(
url + filename, local_filename)
statinfo = os.stat(local_filename)
if sha256 and _hash_file(local_filename) != sha256:
raise Exception('Failed to verify ' + local_filename +
' due to hash '
'mismatch. Can you get to it with a browser?')
if statinfo.st_size == expected_bytes:
print("found and verified", filename)
else:
print(statinfo.st_size)
raise Exception('Failed to verify ' + local_filename +
'. Can you get to it with a browser?')
return local_filename
filename = maybe_download(
'text8.zip',
31344016,
sha256=
'a6640522afe85d1963ad56c05b0ede0a0c000dddc9671758a6cc09b7a38e5232')
# 数据转为List<String>
def read_data(filename):
with zipfile.ZipFile(filename) as f:
data = tf.compat.as_str(f.read(f.namelist()[0])).split()
return data
vocabulary = read_data(filename)
print('data_size', len(vocabulary))
# 第二步，建词典并且把罕见词替换成UNK
vocabulary_size = 50000
def build_dataset(words, n_words):
count = [['UNK', -1]]
count.extend(collections.Counter(words).most_common(n_words - 1))
dictionary = {word: index for index, (word, _) in enumerate(count)}
data = []
unk_count = 0
for word in words:
index = dictionary.get(word, 0)
if index == 0: # dictionary['UNK']
unk_count += 1
data.append(index)
count[0][1] = unk_count
reversed_dictionary = dict(zip(dictionary.values(), dictionary.keys()))
return data, count, dictionary, reversed_dictionary
# data: 词表中的所有的词的id
# count： 单词和出现次数的map
# dictionary： 单词-->index 的映射
# reverse_dictionary:index -->单词
data, count, dictionary, reversed_dictionary = build_dataset(
vocabulary, vocabulary_size)
del vocabulary
print('Most common words (+UNK)', count[:5])
print('Sample data', data[:10],
[reversed_dictionary[i] for i in data[:10]])
# 针对skip-gram模型生成batch数据
def generate_batch(batch_size, num_skips, skip_window):
global data_index
assert batch_size % num_skips == 0
assert num_skips <= 2 * skip_window
batch = np.ndarray(shape=(batch_size), dtype=np.int32)
labels = np.ndarray(shape=(batch_size, 1), dtype=np.int32)
# skip的范围
span = 2 * skip_window + 1
buffer = collections.deque(maxlen=span)
if data_index + span > len(data):
data_index = 0
buffer.extend(data[data_index:data_index + span]) # 向后取一个窗口内的结果
data_index += span
for i in range(batch_size // num_skips):
context_words = [w for w in range(span) if w != skip_window]
words_to_use = random.sample(context_words, num_skips)
for j, context_words in enumerate(words_to_use):
batch[i * num_skips + j] = buffer[skip_window]
labels[i * num_skips + j, 0] = buffer[context_words]
if data_index == len(data):
buffer.extend(data[0:span])
data_index = span
else:
buffer.append(data[data_index])
data_index += 1
# Backtrack a little bit to avoid skipping words in the end of a batch
data_index = (data_index - span) % len(data)
return batch, labels
batch, labels = generate_batch(batch_size=8, num_skips=2, skip_window=1)
for i in range(8):
print(batch[i], reversed_dictionary[batch[i]], '->', labels[i, 0],
reversed_dictionary[labels[i, 0]])
# 建立并且训练模型
batch_size = 128
embedding_size = 128 # 词向量维度
skip_window = 1 # 考虑左右几个单词
num_skips = 2 # 复用输入生成标签的次数
num_sampled = 64 # 负样本数量
# 采样一个样本的近邻作为随机验证机，将验证集样本限制为 较低id的单词，是比较高频的构造词汇
# 这三个变量用作显示模型准确率，不影响计算。
valid_size = 16 # 用于评估相似性的随机单词集合
valid_window = 100 #
valid_examples = np.random.choice(valid_window, valid_size, replace=False)
graph = tf.Graph()
with graph.as_default():
# 输入数据
with tf.name_scope('input'):
train_inputs = tf.placeholder(tf.int32, shape=[batch_size])
train_labels = tf.placeholder(tf.int32, shape=[batch_size, 1])
valid_dataset = tf.constant(valid_examples, dtype=tf.int32)
# 操作op和变量variables 固定在CPU上。
with tf.device('/cpu:0'):
with tf.name_scope('embeddings'):
embeddings = tf.Variable(
tf.random_uniform([vocabulary_size, embedding_size], -1.0,
1.0))
embed = tf.nn.embedding_lookup(embeddings, train_inputs)
# 构造NCE损失的变量
with tf.name_scope('weights'):
nce_weights = tf.Variable(
tf.truncated_normal([vocabulary_size, embedding_size],
stddev=1.0 /
math.sqrt(embedding_size)))
with tf.name_scope('biases'):
nce_biases = tf.Variable(tf.zeros([vocabulary_size]))
# 计算该批次的平均nce损失，当评估损失的时候，自动绘制一个新的负样本。
with tf.name_scope('loss'):
loss = tf.reduce_mean(
tf.nn.nce_loss(weights=nce_weights,
biases=nce_biases,
labels=train_labels,
inputs=embed,
num_sampled=num_sampled,
num_classes=vocabulary_size))
# 汇总损失
tf.summary.scalar('loss', loss)
# 构造SGD
with tf.name_scope('opytimizer'):
optimizer = tf.train.GradientDescentOptimizer(1.0).minimize(loss)
# 计算小批次样本和所有样本之间的余弦相似度
norm = tf.sqrt(tf.reduce_sum(tf.square(embeddings), 1, keep_dims=True))
normalized_embeddings = embeddings / norm
valid_embeddings = tf.nn.embedding_lookup(normalized_embeddings,
valid_dataset)
similarity = tf.matmul(valid_embeddings,
normalized_embeddings,
transpose_b=True)
# merge all summary
merged = tf.summary.merge_all()
init = tf.global_variables_initializer()
saver = tf.train.Saver()
# 开始训练
num_steps = 1000001
with tf.compat.v1.Session(graph=graph) as session:
# 写入摘要
writer = tf.summary.FileWriter(log_dir, session.graph)
init.run()
print('inited..')
average_loss = 0
for step in range(num_steps):
batch_inputs, batch_labels = generate_batch(
batch_size, num_skips, skip_window)
feed_dict = {
train_inputs: batch_inputs,
train_labels: batch_labels
}
# 定义元变量
run_metadata = tf.RunMetadata()
_, summary, loss_val = session.run([optimizer, merged, loss],
feed_dict=feed_dict,
run_metadata=run_metadata)
average_loss += loss_val
writer.add_summary(summary, step)
if step == (num_steps - 1):
writer.add_run_metadata(run_metadata, 'step%d' % step)
if step % 2000 == 0:
if step > 0:
average_loss /= 2000
# 平均损失是对最近的2000个批次样本的估计。
print('Average loss at step ', step, ': ', average_loss)
average_loss = 0
if step % 10000 == 0:
sim = similarity.eval()
for i in range(valid_size):
valid_word = reversed_dictionary[valid_examples[i]]
top_k = 8
nearest = (-sim[i, :]).argsort()[1:top_k + 1]
log_str = 'Nearest to %s:' % valid_word
print(
log_str, ', '.join([
reversed_dictionary[nearest[k]]
for k in range(top_k)
]))
final_embeddings = normalized_embeddings.eval()
# 写下embedding的相应标签
with open(log_dir + '/metadata.tsv', 'w') as f:
for i in range(vocabulary_size):
f.write(reversed_dictionary[i] + '\n')
# 保存checkpoint
saver.save(session, os.path.join(log_dir, 'model.ckpt'))
# 配置Tensorboard
config = projector.ProjectorConfig()
embedding_conf = config.embeddings.add()
embedding_conf.tensor_name = embeddings.name
embedding_conf.metadata_path = os.path.join(log_dir, 'metadata.tsv')
projector.visualize_embeddings(writer, config)
writer.close()
# Step 6: Visualize the embeddings.
# pylint: disable=missing-docstring
# Function to draw visualization of distance between embeddings.
def plot_with_labels(low_dim_embs, labels, filename):
assert low_dim_embs.shape[0] >= len(
labels), 'More labels than embeddings'
plt.figure(figsize=(18, 18)) # in inches
for i, label in enumerate(labels):
x, y = low_dim_embs[i, :]
plt.scatter(x, y)
plt.annotate(label,
xy=(x, y),
xytext=(5, 2),
textcoords='offset points',
ha='right',
va='bottom')
plt.savefig(filename)
try:
# pylint: disable=g-import-not-at-top
from sklearn.manifold import TSNE
import matplotlib.pyplot as plt
tsne = TSNE(perplexity=30,
n_components=2,
init='pca',
n_iter=5000,
method='exact')
plot_only = 500
low_dim_embs = tsne.fit_transform(final_embeddings[:plot_only, :])
labels = [reversed_dictionary[i] for i in xrange(plot_only)]
plot_with_labels(low_dim_embs, labels,
os.path.join(gettempdir(), 'tsne.png'))
except ImportError as ex:
print(
'Please install sklearn, matplotlib, and scipy to show embeddings.'
)
print(ex)
train_epochs = 25
batch_size = 100
display_step = 1
# 定义placeholder
x = tf.placeholder(tf.float32, [None, 784])
y = tf.placeholder(tf.float32, [None, 10])
# weights bias
W = tf.Variable(tf.zeros([784, 10]))
b = tf.Variable(tf.zeros([10]))
pred = tf.nn.softmax(tf.matmul(x, W) + b)
# 最小化交叉熵
cost = tf.reduce_mean(-tf.reduce_sum(y * tf.log(pred), reduction_indices=1))
# 梯度下降
optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(cost)
# 初始化所有参数
init = tf.global_variables_initializer()
with tf.Session() as sess:
# 运行初始化
sess.run(init)
for epoch in range(train_epochs):
avg_cost = 0.
total_batch = int(mnist.train.num_examples / batch_size)
# 循环所有的batchs
for i in range(total_batch):
from com.hiekn.tensorflow.Mnist_TF_work_1_2 import input_data
import tensorflower as tf
mnist = input_data.read_data_sets('MNIST_data',one_hot=True)
sess = tf.InteractiveSession()
x = tf.placeholder("float",shape=[None,784])
y_ = tf.placeholder("float",shape=[None,10])
W = tf.Variable(tf.zeros([784,10]))
b = tf.Variable(tf.zeros([10]))
sess.run(tf.initialize_all_variables())
y = tf.nn.softmax(tf.matmul(x,W)+b)
cross_entropy = -tf.reduce_sum(y_*tf.log(y))
train_step = tf.train.GradientDescentOptimizer(0.01).minimize(cross_entropy)
for i in range(1000):
batch = mnist.train.next_batch(50)
train_step.run(feed_dict={x:batch[0],y_:batch[1]})
correct_prediction = tf.equal(tf.argmax(y,1),tf.argmax(y_,1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction,"float"))
print(accuracy.eval(feed_dict={x: mnist.test.images, y_: mnist.test.labels}))
def multihead_attention(queries,
keys,
num_units=None,
num_heads=0,
dropout_rate=0,
is_training=True,
causality=False,
scope="multihead_attention",
reuse=None):
with tf.variable_scope(scope, reuse=reuse):
if num_units is None:
num_units = queries.get_shape().as_list()[-1]
# linear projection
Q = tf.layers.dense(queries, num_units, activation=tf.nn.relu)
K = tf.layers.dense(keys, num_units, activation=tf.nn.relu)
V = tf.layers.dense(keys, num_units, activation=tf.nn.relu)
# split and concat
Q_ = tf.concat(tf.split(Q, num_heads, axis=2), axis=0)
K_ = tf.concat(tf.split(K, num_heads, axis=2), axis=0)
V_ = tf.concat(tf.split(V, num_heads, axis=2), axis=0)
outputs = tf.matmul(Q_, tf.transpose(K_, [0, 2, 1]))
outputs = outputs / (K_.get_shape().as_list()[-1]**0.5)
# mask
key_masks = tf.sign(tf.abs(tf.reduce_sum(keys, axis=-1)))
key_masks = tf.tile(key_masks, [num_heads, 1])
key_masks = tf.tile(tf.expand_dims(key_masks, 1),
[1, tf.shape(queries)[1], 1])
paddings = tf.ones_like(outputs) * (-2**32 + 1)
outputs = tf.where(tf.equal(key_masks, 0), paddings, outputs)
# masked from future
if causality:
diag_vals = tf.ones_like(outputs[0, :, :])
tril = tf.contrib.linalg.LinearOperatorTril(diag_vals).to_dense()
masks = tf.tile(tf.expand_dims(tril, 0),
[tf.shape(outputs)[0], 1, 1])
paddings = tf.ones_like(masks) * (-2**32 + 1)
outputs = tf.where(tf.equal(masks, 0), paddings, outputs)
outputs = tf.nn.softmax(outputs)
# query mask
query_masks = tf.sign(tf.abs(tf.reduce_sum(queries, axis=-1)))
query_masks = tf.tile(query_masks, [num_heads, 1])
query_masks = tf.tile(tf.expand_dims(query_masks, -1),
[1, 1, tf.shape(keys)[1]])
outputs *= query_masks
outputs = tf.layers.dropout(outputs,
rate=dropout_rate,
training=tf.convert_to_tensor(is_training))
outputs = tf.matmul(outputs, V_)
# restore shape
outputs = tf.concat(tf.split(outputs, num_heads, axis=0), axis=2)
outputs += queries
outputs = normalize(outputs)
return outputs
print("开始下载数据集..")
mnist = input_data.read_data_sets('MNIST_data', one_hot=True)
print("下载完毕..")
sess = tf.InteractiveSession()
# 该函数可以更加灵活的构建代码，可以在运行计算的图的时候通过operation操作插入一些计算图。
x = tf.placeholder("float", shape=[None, 784])
y_ = tf.placeholder("float", shape=[None, 10]) # 占位符
W = tf.Variable(tf.zeros([784, 10]))
b = tf.Variable(tf.zeros([10])) # 变量，跟占位符一样作为额外的输入量
sess.run(tf.initialize_all_variables())
y = tf.nn.softmax(tf.matmul(x, W) + b) # 使用softmax计算每个分类的概率
cross_entropy = -tf.reduce_sum(y_ * tf.log(y)) # 交叉熵
train_step = tf.train.GradientDescentOptimizer(0.01).minimize(
cross_entropy) # 训练使用最小梯度下降，且最小化交叉熵loss
init = tf.global_variables_initializer()
for i in range(1000):
batch = mnist.train.next_batch(50) # load mini-batchsize dataset
train_step.run(feed_dict={x: batch[0], y_: batch[1]})
print("训练结束..")
"""
这段表达特别好：tf.argmax 是一个非常有用的函数，它能给出某个tensor对象在某一维上的其数据最大值所在的索引值。
由于标签向量是由0,1组成，因此最大值1所在的索引位置就是类别标签，比如tf.argmax(y,1)返回的是模型对于任一输入x预测到的标签值，
而 tf.argmax(y_,1) 代表正确的标签，我们可以用 tf.equal 来检测我们的预测是否真实标签匹配(索引位置一样表示匹配)。
"""
correct_prediction = tf.equal(tf.argmax(y, 1), tf.argmax(y_, 1))
accuarcy = tf.reduce_mean(tf.cast(correct_prediction, "float"))
def evaluation(logits, labels):
correct = tf.nn.in_top_k(predictions=logits, targets=labels, k=1)
return tf.reduce_sum(input_tensor=tf.cast(correct, tf.int32))
3.465, 1.65, 2.904, 2.42, 2.94, 1.3
])
n_samples = train_x.shape[0]
X = tf.placeholder(tf.float32)
Y = tf.placeholder(tf.float32)
W = tf.Variable(rng.randn(), name="weights")
b = tf.Variable(rng.randn(), name="bias")
# 创建一个线性模型
pred = tf.add(tf.multiply(X, W), b)
# 设置损失函数（均方损失函数）
cost = tf.reduce_sum(tf.pow(pred - Y, 2)) / (2 * n_samples)
# 梯度下降
optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(cost)
# init
init = tf.global_variables_initializer()
# 开始训练
with tf.Session() as sess:
# 运行初始化
sess.run(init)
# 填充所有训练数据
for epoch in range(training_epochs):
for (x, y) in zip(train_x, train_y):
def mean_square_fn(model_fn, inputs, labels):
return tf.reduce_sum(tf.pow(model_fn(inputs) - labels,
2)) / (2 * n_samples)