张量流中的深度学习全连接神经网络

Question

我正在阅读有关使用张量流进行深度学习的信息，该书使用的张量流用于深度学习，作者是Bharath RamSundar等。在这里，作者在第5章中实现如下

import numpy as np
np.random.seed(456)
import  tensorflow as tf
tf.set_random_seed(456)
import matplotlib.pyplot as plt
import deepchem as dc
from sklearn.metrics import accuracy_score

def eval_tox21_hyperparams(n_hidden=50, n_layers=1, learning_rate=.001,
                           dropout_prob=0.5, n_epochs=45, batch_size=100,
                           weight_positives=True):

  print("---------------------------------------------")
  print("Model hyperparameters")
  print("n_hidden = %d" % n_hidden)
  print("n_layers = %d" % n_layers)
  print("learning_rate = %f" % learning_rate)
  print("n_epochs = %d" % n_epochs)
  print("batch_size = %d" % batch_size)
  print("weight_positives = %s" % str(weight_positives))
  print("dropout_prob = %f" % dropout_prob)
  print("---------------------------------------------")

  d = 1024
  graph = tf.Graph()
  with graph.as_default():
    _, (train, valid, test), _ = dc.molnet.load_tox21()
    train_X, train_y, train_w = train.X, train.y, train.w
    valid_X, valid_y, valid_w = valid.X, valid.y, valid.w
    test_X, test_y, test_w = test.X, test.y, test.w

    # Remove extra tasks
    train_y = train_y[:, 0]
    valid_y = valid_y[:, 0]
    test_y = test_y[:, 0]
    train_w = train_w[:, 0]
    valid_w = valid_w[:, 0]
    test_w = test_w[:, 0]

    # Generate tensorflow graph
    with tf.name_scope("placeholders"):
      x = tf.placeholder(tf.float32, (None, d))
      y = tf.placeholder(tf.float32, (None,))
      w = tf.placeholder(tf.float32, (None,))
      keep_prob = tf.placeholder(tf.float32)
    for layer in range(n_layers):
      with tf.name_scope("layer-%d" % layer):
        W = tf.Variable(tf.random_normal((d, n_hidden))) **-------------> Question here?**
        b = tf.Variable(tf.random_normal((n_hidden,)))
        x_hidden = tf.nn.relu(tf.matmul(x, W) + b)
        # Apply dropout
        x_hidden = tf.nn.dropout(x_hidden, keep_prob)
    with tf.name_scope("output"):
      W = tf.Variable(tf.random_normal((n_hidden, 1)))
      b = tf.Variable(tf.random_normal((1,)))
      y_logit = tf.matmul(x_hidden, W) + b
      # the sigmoid gives the class probability of 1
      y_one_prob = tf.sigmoid(y_logit)
      # Rounding P(y=1) will give the correct prediction.
      y_pred = tf.round(y_one_prob)
    with tf.name_scope("loss"):
      # Compute the cross-entropy term for each datapoint
      y_expand = tf.expand_dims(y, 1)
      entropy = tf.nn.sigmoid_cross_entropy_with_logits(logits=y_logit, labels=y_expand)
      # Multiply by weights
      if weight_positives:
        w_expand = tf.expand_dims(w, 1)
        entropy = w_expand * entropy
      # Sum all contributions
      l = tf.reduce_sum(entropy)

    with tf.name_scope("optim"):
      train_op = tf.train.AdamOptimizer(learning_rate).minimize(l)

    with tf.name_scope("summaries"):
      tf.summary.scalar("loss", l)
      merged = tf.summary.merge_all()

    hyperparam_str = "d-%d-hidden-%d-lr-%f-n_epochs-%d-batch_size-%d-weight_pos-%s" % (
        d, n_hidden, learning_rate, n_epochs, batch_size, str(weight_positives))
    train_writer = tf.summary.FileWriter('/tmp/fcnet-func-' + hyperparam_str,
                                         tf.get_default_graph())
    N = train_X.shape[0]
    with tf.Session() as sess:
      sess.run(tf.global_variables_initializer())
      step = 0
      for epoch in range(n_epochs):
        pos = 0
        while pos < N:
          batch_X = train_X[pos:pos+batch_size]
          batch_y = train_y[pos:pos+batch_size]
          batch_w = train_w[pos:pos+batch_size]
          feed_dict = {x: batch_X, y: batch_y, w: batch_w, keep_prob: dropout_prob}
          _, summary, loss = sess.run([train_op, merged, l], feed_dict=feed_dict)
          print("epoch %d, step %d, loss: %f" % (epoch, step, loss))
          train_writer.add_summary(summary, step)

          step += 1
          pos += batch_size

      # Make Predictions (set keep_prob to 1.0 for predictions)
      valid_y_pred = sess.run(y_pred, feed_dict={x: valid_X, keep_prob: 1.0})

    weighted_score = accuracy_score(valid_y, valid_y_pred, sample_weight=valid_w)
    print("Valid Weighted Classification Accuracy: %f" % weighted_score)
  return weighted_score

假设我们有两个隐藏的层，每层50个单位。输入形状为（样本数，nx），其中 nx是功能数量。

假设nx为1024。

W1 =（1024，50） W2 =（50，50）。

但是在这里，作者编写的代码如下（大小写始终为（1024，50））。我觉得有些事情 在这里错了吗？我的理解是对的吗？如何在下面的示例中使用for循环纠正此问题？ 感谢您的时间和帮助。

for layer in range(n_layers):
      with tf.name_scope("layer-%d" % layer):
        W = tf.Variable(tf.random_normal((d, n_hidden))) **-------------> Question here?**
        b = tf.Variable(tf.random_normal((n_hidden,)))
        x_hidden = tf.nn.relu(tf.matmul(x, W) + b)
        # Apply dropout
        x_hidden = tf.nn.dropout(x_hidden, keep_prob)