本文實例為大家分享了Tensorflow實現AlexNet卷積神經網絡的具體實現代碼，供大家參考，具體內容如下

之前已經介紹過了AlexNet的網絡構建了，這次主要不是為了訓練數據，而是為了對每個batch的前饋（Forward）和反饋（backward）的平均耗時進行計算。在設計網絡的過程中，分類的結果很重要，但是運算速率也相當重要。尤其是在跟蹤（Tracking）的任務中，如果使用的網絡太深，那么也會導致實時性不好。

from datetime import datetimeimport mathimport timeimport tensorflow as tfbatch_size = 32num_batches = 100def print_activations(t): print(t.op.name, '', t.get_shape().as_list())def inference(images): parameters = [] with tf.name_scope('conv1') as scope:  kernel = tf.Variable(tf.truncated_normal([11, 11, 3, 64], dtype = tf.float32, stddev = 1e-1), name = 'weights')  conv = tf.nn.conv2d(images, kernel, [1, 4, 4, 1], padding = 'SAME')  biases = tf.Variable(tf.constant(0.0, shape = [64], dtype = tf.float32), trainable = True, name = 'biases')  bias = tf.nn.bias_add(conv, biases)  conv1 = tf.nn.relu(bias, name = scope)  print_activations(conv1)  parameters += [kernel, biases]  lrn1 = tf.nn.lrn(conv1, 4, bias = 1.0, alpha = 0.001 / 9, beta = 0.75, name = 'lrn1')  pool1 = tf.nn.max_pool(lrn1, ksize = [1, 3, 3, 1], strides = [1, 2, 2, 1], padding = 'VALID', name = 'pool1')  print_activations(pool1) with tf.name_scope('conv2') as scope:  kernel = tf.Variable(tf.truncated_normal([5, 5, 64, 192], dtype = tf.float32, stddev = 1e-1), name = 'weights')  conv = tf.nn.conv2d(pool1, kernel, [1, 1, 1, 1], padding = 'SAME')  biases = tf.Variable(tf.constant(0.0, shape = [192], dtype = tf.float32), trainable = True, name = 'biases')  bias = tf.nn.bias_add(conv, biases)  conv2 = tf.nn.relu(bias, name = scope)  parameters += [kernel, biases]  print_activations(conv2)  lrn2 = tf.nn.lrn(conv2, 4, bias = 1.0, alpha = 0.001 / 9, beta = 0.75, name = 'lrn2')  pool2 = tf.nn.max_pool(lrn2, ksize = [1, 3, 3, 1], strides = [1, 2, 2, 1], padding = 'VALID', name = 'pool2')  print_activations(pool2) with tf.name_scope('conv3') as scope:  kernel = tf.Variable(tf.truncated_normal([3, 3, 192, 384], dtype = tf.float32, stddev = 1e-1), name = 'weights')  conv = tf.nn.conv2d(pool2, kernel, [1, 1, 1, 1], padding = 'SAME')  biases = tf.Variable(tf.constant(0.0, shape = [384], dtype = tf.float32), trainable = True, name = 'biases')  bias = tf.nn.bias_add(conv, biases)  conv3 = tf.nn.relu(bias, name = scope)  parameters += [kernel, biases]  print_activations(conv3) with tf.name_scope('conv4') as scope:  kernel = tf.Variable(tf.truncated_normal([3, 3, 384, 256], dtype = tf.float32, stddev = 1e-1), name = 'weights')  conv = tf.nn.conv2d(conv3, kernel, [1, 1, 1, 1], padding = 'SAME')  biases = tf.Variable(tf.constant(0.0, shape = [256], dtype = tf.float32), trainable = True, name = 'biases')  bias = tf.nn.bias_add(conv, biases)  conv4 = tf.nn.relu(bias, name = scope)  parameters += [kernel, biases]  print_activations(conv4) with tf.name_scope('conv5') as scope:  kernel = tf.Variable(tf.truncated_normal([3, 3, 256, 256], dtype = tf.float32, stddev = 1e-1), name = 'weights')  conv = tf.nn.conv2d(conv4, kernel, [1, 1, 1, 1], padding = 'SAME')  biases = tf.Variable(tf.constant(0.0, shape = [256], dtype = tf.float32), trainable = True, name = 'biases')  bias = tf.nn.bias_add(conv, biases)  conv5 = tf.nn.relu(bias, name = scope)  parameters += [kernel, biases]  print_activations(conv5)  pool5 = tf.nn.max_pool(conv5, ksize = [1, 3, 3, 1], strides = [1, 2, 2, 1], padding = 'VALID', name = 'pool5')  print_activations(pool5)  return pool5, parametersdef time_tensorflow_run(session, target, info_string): num_steps_burn_in = 10 total_duration = 0.0 total_duration_squared = 0.0 for i in range(num_batches + num_steps_burn_in):  start_time = time.time()  _ = session.run(target)  duration = time.time() - start_time  if i >= num_steps_burn_in:   if not i % 10:    print('%s: step %d, duration = %.3f' %(datetime.now(), i - num_steps_burn_in, duration))   total_duration += duration   total_duration_squared += duration * duration mn = total_duration / num_batches vr = total_duration_squared / num_batches - mn * mn sd = math.sqrt(vr) print('%s: %s across %d steps, %.3f +/- %.3f sec / batch' %(datetime.now(), info_string, num_batches, mn, sd))def run_benchmark(): with tf.Graph().as_default():  image_size = 224  images = tf.Variable(tf.random_normal([batch_size, image_size, image_size, 3], dtype = tf.float32, stddev = 1e-1))  pool5, parameters = inference(images)  init = tf.global_variables_initializer()  sess = tf.Session()  sess.run(init)  time_tensorflow_run(sess, pool5, "Forward")  objective = tf.nn.l2_loss(pool5)  grad = tf.gradients(objective, parameters)  time_tensorflow_run(sess, grad, "Forward-backward")run_benchmark()