Tensorflow--MNIST手寫資料集全連線層分類
阿新 • • 發佈:2019-02-13
手寫資料集分類一般都被用來當做tensorflow入門的教程。當然啦,神經網路一般分為全連線層(FC),卷積層(CNN)和序列模型(RNN),這裡先用全連線層做一個分類。
我就把之前寫的程式碼貼上來吧。
# 用tensorflow 匯入資料 from tensorflow.examples.tutorials.mnist import input_data mnist = input_data.read_data_sets('MNIST_data', one_hot=True) # 權值初始化 def weight_variable(shape): # 用正態分佈來初始化權值 initial = tf.truncated_normal(shape, stddev=0.1) return tf.Variable(initial) def bias_variable(shape): # 本例中用relu啟用函式,所以用一個很小的正偏置較好 initial = tf.constant(0.1, shape=shape) return tf.Variable(initial) # input_layer X_ = tf.placeholder(tf.float32, [None, 784]) y_ = tf.placeholder(tf.float32, [None, 10]) # FC1 W_fc1 = weight_variable([784, 1024]) b_fc1 = bias_variable([1024]) h_fc1 = tf.nn.relu(tf.matmul(X_, W_fc1) + b_fc1) # FC2 W_fc2 = weight_variable([1024, 10]) b_fc2 = bias_variable([10]) y_pre = tf.nn.softmax(tf.matmul(h_fc1, W_fc2) + b_fc2) # 1.損失函式:cross_entropy cross_entropy = -tf.reduce_sum(y_ * tf.log(y_pre)) # y_ 中只有標籤所在的那一類是 1, 其餘全部都是0. # 2.優化函式:AdamOptimizer, 優化速度要比 GradientOptimizer 快很多 train_step = tf.train.AdamOptimizer(0.001).minimize(cross_entropy) # 3.預測結果評估 # 預測值中最大值(1)即分類結果,是否等於原始標籤中的(1)的位置。argmax()取最大值所在的下標 correct_prediction = tf.equal(tf.argmax(y_pre, 1), tf.arg_max(y_, 1)) accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32)) # 開始執行 sess.run(tf.global_variables_initializer()) # 這大概迭代了不到 10 個 epoch, 訓練準確率已經達到了0.98 for i in range(5000): X_batch, y_batch = mnist.train.next_batch(batch_size=100) train_step.run(feed_dict={X_: X_batch, y_: y_batch}) if (i+1) % 200 == 0: train_accuracy = accuracy.eval(feed_dict={X_: mnist.train.images, y_: mnist.train.labels}) print "step %d, training acc %g" % (i+1, train_accuracy) if (i+1) % 1000 == 0: test_accuracy = accuracy.eval(feed_dict={X_: mnist.test.images, y_: mnist.test.labels}) print "= " * 10, "step %d, testing acc %g" % (i+1, test_accuracy)