Python clip_ops.global_norm函数代码示例

def add_gradients_summaries(grads_and_vars):
  """Add summaries to gradients.

  Args:
    grads_and_vars: A list of gradient to variable pairs (tuples).

  Returns:
    The list of created summaries.
  """
  summaries = []
  for grad, var in grads_and_vars:
    if grad is not None:
      if isinstance(grad, ops.IndexedSlices):
        grad_values = grad.values
      else:
        grad_values = grad
      summaries.append(
          summary.histogram(var.op.name + '_gradient', grad_values))
      summaries.append(
          summary.scalar(var.op.name + '_gradient_norm',
                         clip_ops.global_norm([grad_values])))
    else:
      logging.info('Var %s has no gradient', var.op.name)

  return summaries

def clip_gradients_by_global_norm(gradients_variables, clip_norm=20.):
  """Clips gradients of a multitask loss by their global norm.
  Ignores all-zero tensors when computing the global norm.

  Args:
  gradients_variables: a list of pairs (gradient, variable).
  clip_norm: a float Tensor, the global norm to clip on. Default is 20.0.

  Returns:
  list: A list of pairs of the same type as gradients_variables,.
  fixed_global_norm: A 0-D (scalar) Tensor representing the global norm.
  """
  gradients, variables = six.moves.zip(*gradients_variables)
  def _replace_nonexisting_grad(grad):
    if grad is None:
      return grad
    all_zeros = _is_all_zeros(grad)
    return control_flow_ops.cond(all_zeros,
                                 lambda: array_ops.zeros(
                                     [], dtype=dtypes.as_dtype(grad.dtype)),
                                 lambda: grad)
  nonzero_gradients = [_replace_nonexisting_grad(g) for g in gradients]
  fixed_global_norm = clip_ops.global_norm(nonzero_gradients)
  gradients, _ = clip_ops.clip_by_global_norm(gradients, clip_norm,
                                              use_norm=fixed_global_norm)
  return list(six.moves.zip(gradients, variables)), fixed_global_norm

  def gradient_clipping(grads_and_vars):
    """Internal function for adaptive clipping."""
    grads, variables = zip(*grads_and_vars)

    norm = clip_ops.global_norm(grads)

    max_norm, log_mean = _adaptive_max_norm(norm, std_factor, decay,
                                            global_step, epsilon, name)

    # reports the max gradient norm for debugging
    if report_summary:
      summary.scalar("global_norm/adaptive_max_gradient_norm", max_norm)

    # factor will be 1. if norm is smaller than max_norm
    factor = array_ops.where(norm < max_norm,
                             array_ops.ones_like(norm),
                             math_ops.exp(log_mean) / norm)

    if static_max_norm is not None:
      factor = math_ops.minimum(static_max_norm / norm, factor)

    # apply factor
    clipped_grads = []
    for grad in grads:
      if grad is None:
        clipped_grads.append(None)
      elif isinstance(grad, ops.IndexedSlices):
        clipped_grads.append(
            ops.IndexedSlices(grad.values * factor, grad.indices,
                              grad.dense_shape))
      else:
        clipped_grads.append(grad * factor)

    return list(zip(clipped_grads, variables))

  def test_stable_global_norm_avoids_overflow(self):
    tensors = [array_ops.ones([4]), array_ops.ones([4, 4]) * 1e19, None]
    gnorm_is_inf = math_ops.is_inf(clip_ops.global_norm(tensors))
    stable_gnorm_is_inf = math_ops.is_inf(
        tfgan_losses._numerically_stable_global_norm(tensors))

    with self.test_session(use_gpu=True):
      self.assertTrue(gnorm_is_inf.eval())
      self.assertFalse(stable_gnorm_is_inf.eval())

  def test_stable_global_norm_unchanged(self):
    """Test that preconditioning doesn't change global norm value."""
    random_seed.set_random_seed(1234)
    tensors = [random_ops.random_uniform([3]*i, -10.0, 10.0) for i in range(6)]
    gnorm = clip_ops.global_norm(tensors)
    precond_gnorm = tfgan_losses._numerically_stable_global_norm(tensors)

    with self.test_session(use_gpu=True) as sess:
      for _ in range(10):  # spot check closeness on more than one sample.
        gnorm_np, precond_gnorm_np = sess.run([gnorm, precond_gnorm])
        self.assertNear(gnorm_np, precond_gnorm_np, 1e-5)

def _numerically_stable_global_norm(tensor_list):
  """Compute the global norm of a list of Tensors, with improved stability.

  The global norm computation sometimes overflows due to the intermediate L2
  step. To avoid this, we divide by a cheap-to-compute max over the
  matrix elements.

  Args:
    tensor_list: A list of tensors, or `None`.

  Returns:
    A scalar tensor with the global norm.
  """
  if np.all([x is None for x in tensor_list]):
    return 0.0

  list_max = math_ops.reduce_max([math_ops.reduce_max(math_ops.abs(x)) for x in
                                  tensor_list if x is not None])
  return list_max * clip_ops.global_norm([x / list_max for x in tensor_list
                                          if x is not None])

  def model_fn(features, labels, mode, params):
    """Model function defining an inpainting estimator."""
    batch_size = params['batch_size']
    z_shape = [batch_size] + params['z_shape']
    add_summaries = params['add_summaries']
    input_clip = params['input_clip']

    z = variable_scope.get_variable(
        name=INPUT_NAME, initializer=random_ops.truncated_normal(z_shape),
        constraint=lambda x: clip_ops.clip_by_value(x, -input_clip, input_clip))

    generator = functools.partial(generator_fn, mode=mode)
    discriminator = functools.partial(discriminator_fn, mode=mode)
    gan_model = tfgan_train.gan_model(generator_fn=generator,
                                      discriminator_fn=discriminator,
                                      real_data=labels,
                                      generator_inputs=z,
                                      check_shapes=False)

    loss = loss_fn(gan_model, features, labels, add_summaries)

    # Use a variable scope to make sure that estimator variables dont cause
    # save/load problems when restoring from ckpts.
    with variable_scope.variable_scope(OPTIMIZER_NAME):
      opt = optimizer(learning_rate=params['learning_rate'],
                      **params['opt_kwargs'])
      train_op = opt.minimize(
          loss=loss, global_step=training_util.get_or_create_global_step(),
          var_list=[z])

    if add_summaries:
      z_grads = gradients_impl.gradients(loss, z)
      summary.scalar('z_loss/z_grads', clip_ops.global_norm(z_grads))
      summary.scalar('z_loss/loss', loss)

    return model_fn_lib.EstimatorSpec(mode=mode,
                                      predictions=gan_model.generated_data,
                                      loss=loss,
                                      train_op=train_op)

#.........这里部分代码省略.........
      h_conv2_flat = tf.reshape(h_conv2, [-1, D*filt_2[0]])
      h_fc1 = tf.nn.relu(tf.matmul(h_conv2_flat, W_fc1) + b_fc1)

    with tf.name_scope("Fully_Connected2") as scope:
      W_fc2 = weight_variable([num_fc_1,num_fc_2], 'Fully_Connected_layer_2')
      b_fc2 = bias_variable([num_fc_2], 'bias_for_Fully_Connected_Layer_2')
      h_fc2 = tf.nn.relu(tf.matmul(h_fc1, W_fc2) + b_fc2)  


    with tf.name_scope("Output") as scope:
        #postfix _o represent variables for output layer
      h_o_drop = tf.nn.dropout(h_fc2, keep_prob)
      W_o = tf.Variable(tf.truncated_normal([num_fc_2, 1], stddev=0.1),name = 'W_o')
      b_o = tf.Variable(tf.constant(0.1, shape=[1]),name = 'b_o')
      h_o = tf.matmul(h_o_drop, W_o) + b_o
      sm_o = tf.sigmoid(h_o)

    with tf.name_scope("Sigmoid") as scope:
        loss = tf.square(sm_o-tf.to_float(y_))
        cost = tf.reduce_mean(loss)
        loss_summ = tf.scalar_summary("cross entropy_loss", cost)
    with tf.name_scope("train") as scope:
        tvars = tf.trainable_variables()
        #We clip the gradients to prevent explosion
        grads = tf.gradients(cost, tvars)
        optimizer = tf.train.AdamOptimizer(learning_rate)
        gradients = zip(grads, tvars)
        train_step = optimizer.apply_gradients(gradients)
        # The following block plots for every trainable variable
        #  - Histogram of the entries of the Tensor
        #  - Histogram of the gradient over the Tensor
        #  - Histogram of the grradient-norm over the Tensor
        numel = tf.constant([[0]])
        for gradient, variable in gradients:
          if isinstance(gradient, ops.IndexedSlices):
            grad_values = gradient.values
          else:
            grad_values = gradient

          numel +=tf.reduce_sum(tf.size(variable))  

          h1 = tf.histogram_summary(variable.name, variable)
          h2 = tf.histogram_summary(variable.name + "/gradients", grad_values)
          h3 = tf.histogram_summary(variable.name + "/gradient_norm", clip_ops.global_norm([grad_values]))
        #tf.gradients returns a list. We cannot fetch a list. therefore we fetch the tensor that is the 0-th element of the list
        vis = tf.gradients(loss, x_feed)[0]
    with tf.name_scope("Evaluating_accuracy") as scope:
        correct_prediction = tf.equal(tf.argmax(h_o,1), y_)
        accuracy = tf.reduce_mean(tf.cast(correct_prediction, "float"))
        accuracy_summary = tf.scalar_summary("accuracy", accuracy)


    #Define one op to call all summaries    
    merged = tf.merge_all_summaries()

    # For now, we collect performances in a Numpy array.
    # In future releases, I hope TensorBoard allows for more
    # flexibility in plotting
    perf_collect = np.zeros((4,int(np.floor(max_iterations /100))))

    with tf.Session() as sess:
      writer = tf.train.SummaryWriter('/home/siddhu/FBIRN/cnn/log/', sess.graph)

      sess.run(tf.initialize_all_variables())

      step = 0      # Step is a counter for filling the numpy array perf_collect
      for i in range(max_iterations):
        batch_ind = np.random.choice(N,batch_size,replace=False)

        check = sess.run([size1],feed_dict={ x: X_val, y_: y_val, keep_prob: 1.0, bn_train : False})    
        #print check[0]

        if i==0:
            # Use this line to check before-and-after test accuracy
            result = sess.run(accuracy, feed_dict={ x: X_val, y_: y_val, keep_prob: 1.0, bn_train : False})
            acc_test_before = result
        if i%100 == 0:
          #Check training performance
          result = sess.run([accuracy,cost],feed_dict = { x: X_train, y_: y_train, keep_prob: 1.0, bn_train : False})
          perf_collect[0,step] = result[0] 
          perf_collect[1,step] = result[1]        

          #Check validation performance
          result = sess.run([accuracy,cost,merged], feed_dict={ x: X_val, y_: y_val, keep_prob: 1.0, bn_train : False})
          acc = result[0]
          perf_collect[2,step] = acc
          perf_collect[3,step] = result[1]

          #Write information to TensorBoard
          summary_str = result[2]
          writer.add_summary(summary_str, i)
          writer.flush()  #Don't forget this command! It makes sure Python writes the summaries to the log-file
          #print(" Validation accuracy at %s out of %s is %s" % (i,max_iterations, acc))
          step +=1
        sess.run(train_step,feed_dict={x:X_train[batch_ind], y_: y_train[batch_ind], keep_prob: dropout, bn_train : True})
      #In the next line we also fetch the softmax outputs 
      result = sess.run([accuracy,numel,sm_o, x_pad], feed_dict={ x: X_val, y_: y_val, keep_prob: 1.0, bn_train : False})
      acc_test = result[0]
    tf.reset_default_graph()
    return acc_test

#.........这里部分代码省略.........
    # Make sure update ops are ran before computing loss.
    if update_ops:
      loss = control_flow_ops.with_dependencies(update_ops, loss)

    # Moving average of the loss with decay.
    # TODO(b/30439864): moving_average_decay should be removed.
    if moving_average_decay is not None:
      logging.warn("'moving_average_decay' is deprecated. Please use "
                   "tensorboard's builtin averaging instead.")
      # Generate moving averages of the loss.
      loss_averages = train.ExponentialMovingAverage(moving_average_decay,
                                                     name="avg")
      loss_averages_op = loss_averages.apply([loss])
      logging_ops.scalar_summary("loss/mean", loss_averages.average(loss))
      loss = control_flow_ops.with_dependencies([loss_averages_op], loss)

    # Learning rate variable, with possible decay.
    if (isinstance(learning_rate, ops.Tensor)
        and learning_rate.get_shape().ndims == 0):
      lr = learning_rate
    elif isinstance(learning_rate, float):
      lr = vs.get_variable(
          "learning_rate", [], trainable=False,
          initializer=init_ops.constant_initializer(learning_rate))
    else:
      raise ValueError("Learning rate should be 0d Tensor or float. "
                       "Got %s of type %s" % (
                           str(learning_rate), str(type(learning_rate))))
    if summaries is None:
      summaries = ["loss", "learning_rate"]
    if learning_rate_decay_fn is not None:
      lr = learning_rate_decay_fn(lr, global_step)
      if "learning_rate" in summaries:
        logging_ops.scalar_summary("learning_rate", lr)

    # Create optimizer, given specified parameters.
    if isinstance(optimizer, six.string_types):
      if optimizer not in OPTIMIZER_CLS_NAMES:
        raise ValueError(
            "Optimizer name should be one of [%s], you provided %s."
            % (", ".join(OPTIMIZER_CLS_NAMES), optimizer))
      opt = OPTIMIZER_CLS_NAMES[optimizer](learning_rate=lr)
    elif isinstance(optimizer, type) and issubclass(optimizer,
                                                    optimizer_.Optimizer):
      opt = optimizer(learning_rate=lr)
    elif isinstance(optimizer, optimizer_.Optimizer):
      opt = optimizer
    else:
      raise ValueError("Unrecognized optimizer: should be string, "
                       "subclass of Optimizer or instance of "
                       "subclass of Optimizer. Got %s." % str(optimizer))

    # All trainable variables, if specific variables are not specified.
    if variables is None:
      variables = vars_.trainable_variables()

    # Compute gradients.
    gradients = opt.compute_gradients(loss, variables)

    # Optionally add gradient noise.
    if gradient_noise_scale is not None:
      gradients = _add_scaled_noise_to_gradients(
          gradients, gradient_noise_scale)

    # Multiply some gradients.
    if gradient_multipliers is not None:
      gradients = _multiply_gradients(gradients, gradient_multipliers)

    # Optionally clip gradients by global norm.
    if clip_gradients is not None:
      gradients = _clip_gradients_by_norm(gradients, clip_gradients)

    # Add scalar summary for loss.
    if "loss" in summaries:
      logging_ops.scalar_summary("loss", loss)

    # Add histograms for variables, gradients and gradient norms.
    for gradient, variable in gradients:
      if isinstance(gradient, ops.IndexedSlices):
        grad_values = gradient.values
      else:
        grad_values = gradient

      if grad_values is not None:
        if "gradients" in summaries:
          logging_ops.histogram_summary(variable.name + "/gradients",
                                        grad_values)
        if "gradient_norm" in summaries:
          logging_ops.histogram_summary(variable.name + "/gradient_norm",
                                        clip_ops.global_norm([grad_values]))

    # Create gradient updates.
    grad_updates = opt.apply_gradients(gradients,
                                       global_step=global_step,
                                       name="train")

    # Ensure the train_tensor computes grad_updates.
    train_tensor = control_flow_ops.with_dependencies([grad_updates], loss)

    return train_tensor

    # The following block plots for every trainable variable
    #  - Histogram of the entries of the Tensor
    #  - Histogram of the gradient over the Tensor
    #  - Histogram of the grradient-norm over the Tensor
    numel = tf.constant([[0]])
    for gradient, variable in gradients:
      if isinstance(gradient, ops.IndexedSlices):
        grad_values = gradient.values
      else:
        grad_values = gradient

      numel +=tf.reduce_sum(tf.size(variable))

      h1 = tf.histogram_summary(variable.name, variable)
      h2 = tf.histogram_summary(variable.name + "/gradients", grad_values)
      h3 = tf.histogram_summary(variable.name + "/gradient_norm", clip_ops.global_norm([grad_values]))
with tf.name_scope("Evaluating_accuracy") as scope:
    correct_prediction = tf.equal(tf.argmax(h_fc2,1), y_)
    accuracy = tf.reduce_mean(tf.cast(correct_prediction, "float"))
    accuracy_summary = tf.scalar_summary("accuracy", accuracy)


#Define one op to call all summaries
merged = tf.merge_all_summaries()

def print_tvars():
  tvars = tf.trainable_variables()
  for variable in tvars:
    print(variable.name)
  return
print_tvars()

#.........这里部分代码省略.........
    if isinstance(optimizer, six.string_types):
      if lr is None:
        raise ValueError("Learning rate is None, but should be specified if "
                         "optimizer is string (%s)." % optimizer)
      if optimizer not in OPTIMIZER_CLS_NAMES:
        raise ValueError(
            "Optimizer name should be one of [%s], you provided %s." %
            (", ".join(OPTIMIZER_CLS_NAMES), optimizer))
      opt = OPTIMIZER_CLS_NAMES[optimizer](learning_rate=lr)
    elif (isinstance(optimizer, type) and
          issubclass(optimizer, optimizer_.Optimizer)):
      if lr is None:
        raise ValueError("Learning rate is None, but should be specified if "
                         "optimizer is class (%s)." % optimizer)
      opt = optimizer(learning_rate=lr)
    elif isinstance(optimizer, optimizer_.Optimizer):
      opt = optimizer
    elif callable(optimizer):
      if learning_rate is not None:
        opt = optimizer(lr)
      else:
        opt = optimizer()
      if not isinstance(opt, optimizer_.Optimizer):
        raise ValueError("Unrecognized optimizer: function should return "
                         "subclass of Optimizer. Got %s." % str(opt))
    else:
      raise ValueError("Unrecognized optimizer: should be string, "
                       "subclass of Optimizer, instance of "
                       "subclass of Optimizer or function with one argument. "
                       "Got %s." % str(optimizer))

    # All trainable variables, if specific variables are not specified.
    if variables is None:
      variables = vars_.trainable_variables()

    # Compute gradients.
    gradients = opt.compute_gradients(
        loss,
        variables,
        colocate_gradients_with_ops=colocate_gradients_with_ops)

    # Optionally add gradient noise.
    if gradient_noise_scale is not None:
      gradients = _add_scaled_noise_to_gradients(gradients,
                                                 gradient_noise_scale)

    # Multiply some gradients.
    if gradient_multipliers is not None:
      gradients = _multiply_gradients(gradients, gradient_multipliers)
      if not gradients:
        raise ValueError(
            "Empty list of (gradient, var) pairs encountered. This is most "
            "likely to be caused by an improper value of gradient_multipliers.")

    if "gradient_norm" in summaries:
      summary.scalar("global_norm/gradient_norm",
                     clip_ops.global_norm(list(zip(*gradients))[0]))

    # Optionally clip gradients by global norm.
    if isinstance(clip_gradients, float):
      gradients = _clip_gradients_by_norm(gradients, clip_gradients)
    elif callable(clip_gradients):
      gradients = clip_gradients(gradients)
    elif clip_gradients is not None:
      raise ValueError(
          "Unknown type %s for clip_gradients" % type(clip_gradients))

    # Add scalar summary for loss.
    if "loss" in summaries:
      summary.scalar("loss", loss)

    # Add histograms for variables, gradients and gradient norms.
    for gradient, variable in gradients:
      if isinstance(gradient, ops.IndexedSlices):
        grad_values = gradient.values
      else:
        grad_values = gradient

      if grad_values is not None:
        var_name = variable.name.replace(":", "_")
        if "gradients" in summaries:
          summary.histogram("gradients/%s" % var_name, grad_values)
        if "gradient_norm" in summaries:
          summary.scalar("gradient_norm/%s" % var_name,
                         clip_ops.global_norm([grad_values]))

    if clip_gradients is not None and "gradient_norm" in summaries:
      summary.scalar("global_norm/clipped_gradient_norm",
                     clip_ops.global_norm(list(zip(*gradients))[0]))

    # Create gradient updates.
    grad_updates = opt.apply_gradients(
        gradients,
        global_step=global_step if increment_global_step else None,
        name="train")

    # Ensure the train_tensor computes grad_updates.
    train_tensor = control_flow_ops.with_dependencies([grad_updates], loss)

    return train_tensor

def optimize_loss(loss,
                  global_step,
                  learning_rate,
                  optimizer,
                  clip_gradients=None,
                  moving_average_decay=0.9,
                  learning_rate_decay_fn=None,
                  variables=None):
  """Given loss and parameters for optimizer, returns a training op.

  Args:
    loss: Tensor, 0 dimensional.
    global_step: Tensor, step counter for each update.
    learning_rate: float or Tensor, magnitude of update per each training step.
    optimizer: string or function, used as optimizer for training.
    clip_gradients: float or None, clips gradients by this value.
    moving_average_decay: float or None, takes into account previous loss
                          to make learning smoother due to outliers.
    learning_rate_decay_fn: function, takes learning_rate and global_step
                            Tensors, returns Tensor. Can be used to implement
                            any learning rate decay funcitons.
                            For example: tf.train.exponential_decay.
    variables: list of variables to optimizer or none.

  Returns:
    Training op.

  Raises:
    ValueError: if optimizer is wrong type.
  """
  # Moving average of the loss with decay.
  if moving_average_decay is not None:
    # Generate moving averages of the loss.
    loss_averages = train.ExponentialMovingAverage(moving_average_decay,
                                                   name="avg")
    loss_averages_op = loss_averages.apply([loss])
    logging_ops.scalar_summary("loss/mean", loss_averages.average(loss))
    loss = control_flow_ops.with_dependencies([loss_averages_op], loss)

  # Convert optimizer into the optimizer class.
  if isinstance(optimizer, str):
    opt_cls = OPTIMIZER_CLS_NAMES[optimizer]
  elif callable(optimizer):
    opt_cls = optimizer
  else:
    raise ValueError("Unrecognized optimizer: should be string or function.")

  # Learning rate variable, with possible decay.
  lr = vs.get_variable("learning_rate",
                       [],
                       trainable=False,
                       initializer=init_ops.constant_initializer(learning_rate))
  if learning_rate_decay_fn is not None:
    lr = learning_rate_decay_fn(lr, global_step)

  # Create optimizer.
  opt = opt_cls(learning_rate=lr)

  # All trainable variables, if specific variables are not specified.
  if variables is None:
    variables = vars_.trainable_variables()

  # Compute gradients and clip them if provided.
  gradients = opt.compute_gradients(loss, variables)
  if clip_gradients is not None:
    clipped_gradients, _ = clip_ops.clip_by_global_norm(gradients,
                                                        clip_gradients)
    gradients = zip(clipped_gradients, variables)

  # Add scalar summary for loss.
  logging_ops.scalar_summary("loss", loss)

  # Add histograms for variables, gradients and gradient norms.
  for gradient, variable in gradients:
    if isinstance(gradient, ops.IndexedSlices):
      grad_values = gradient.values
    else:
      grad_values = gradient
    logging_ops.histogram_summary(variable.name, variable)
    logging_ops.histogram_summary(variable.name + "/gradients", grad_values)
    logging_ops.histogram_summary(variable.name + "/gradient_norm",
                                  clip_ops.global_norm([grad_values]))

  # Create gradient updates.
  grad_updates = opt.apply_gradients(gradients,
                                     global_step=global_step,
                                     name="train")
  # Make sure total_loss is valid.
  final_loss = array_ops.check_numerics(loss, "Loss is inf or nan")

  # Ensure the train_tensor computes grad_updates.
  train_tensor = control_flow_ops.with_dependencies([grad_updates], final_loss)

  return train_tensor

  def _get_train_ops(self,
                     loss,
                     tf_variables,
                     global_step,
                     grad_bound=1.25,
                     lr_init=1e-3,
                     lr_dec=0.9,
                     start_decay_step=10000,
                     decay_steps=100,
                     optimizer_type="adam"):
    """Loss optimizer.

    Args:
      loss: scalar tf tensor
      tf_variables: list of training variables, typically
        tf.trainable_variables()
      global_step: global_step
      grad_bound: max gradient norm
      lr_init: initial learning rate
      lr_dec: leaning rate decay coefficient
      start_decay_step: start decaying learning rate after this many steps
      decay_steps: apply decay rate factor at this step intervals
      optimizer_type: optimizer type should be either adam or sgd

    Returns:
      train_op: training op
      learning_rate: scalar learning rate tensor
      grad_norm: l2 norm of the gradient vector
      all_grad_norms: l2 norm of each component
    """
    lr_gstep = global_step - start_decay_step

    def f1():
      return constant_op.constant(lr_init)

    def f2():
      return learning_rate_decay.exponential_decay(lr_init, lr_gstep,
                                                   decay_steps, lr_dec, True)

    learning_rate = control_flow_ops.cond(
        math_ops.less(global_step, start_decay_step),
        f1,
        f2,
        name="learning_rate")

    if optimizer_type == "adam":
      opt = adam.AdamOptimizer(learning_rate)
    elif optimizer_type == "sgd":
      opt = gradient_descent.GradientDescentOptimizer(learning_rate)
    grads_and_vars = opt.compute_gradients(loss, tf_variables)
    grad_norm = clip_ops.global_norm([g for g, v in grads_and_vars])
    all_grad_norms = {}
    clipped_grads = []
    clipped_rate = math_ops.maximum(grad_norm / grad_bound, 1.0)
    for g, v in grads_and_vars:
      if g is not None:
        if isinstance(g, tf_ops.IndexedSlices):
          clipped = g.values / clipped_rate
          norm_square = math_ops.reduce_sum(clipped * clipped)
          clipped = tf_ops.IndexedSlices(clipped, g.indices)
        else:
          clipped = g / clipped_rate
          norm_square = math_ops.reduce_sum(clipped * clipped)
        all_grad_norms[v.name] = math_ops.sqrt(norm_square)
        clipped_grads.append((clipped, v))

    train_op = opt.apply_gradients(clipped_grads, global_step)
    return train_op, learning_rate, grad_norm, all_grad_norms

#.........这里部分代码省略.........
        lr = None
        if learning_rate is not None:
            if isinstance(learning_rate, ops.Tensor) and learning_rate.get_shape().ndims == 0:
                lr = learning_rate
            elif isinstance(learning_rate, float):
                lr = vs.get_variable(
                    "learning_rate", [], trainable=False, initializer=init_ops.constant_initializer(learning_rate)
                )
            else:
                raise ValueError(
                    "Learning rate should be 0d Tensor or float. "
                    "Got %s of type %s" % (str(learning_rate), str(type(learning_rate)))
                )
        if summaries is None:
            summaries = ["loss", "learning_rate"]
        if learning_rate is not None and learning_rate_decay_fn is not None:
            lr = learning_rate_decay_fn(lr, global_step)
            if "learning_rate" in summaries:
                logging_ops.scalar_summary("learning_rate", lr)

        # Create optimizer, given specified parameters.
        if isinstance(optimizer, six.string_types):
            if lr is None:
                raise ValueError(
                    "Learning rate is None, but should be specified if " "optimizer is string (%s)." % optimizer
                )
            if optimizer not in OPTIMIZER_CLS_NAMES:
                raise ValueError(
                    "Optimizer name should be one of [%s], you provided %s."
                    % (", ".join(OPTIMIZER_CLS_NAMES), optimizer)
                )
            opt = OPTIMIZER_CLS_NAMES[optimizer](learning_rate=lr)
        elif isinstance(optimizer, type) and issubclass(optimizer, optimizer_.Optimizer):
            if lr is None:
                raise ValueError(
                    "Learning rate is None, but should be specified if " "optimizer is class (%s)." % optimizer
                )
            opt = optimizer(learning_rate=lr)
        elif isinstance(optimizer, optimizer_.Optimizer):
            opt = optimizer
        elif callable(optimizer):
            if learning_rate is not None:
                opt = optimizer(lr)
            else:
                opt = optimizer()
            if not isinstance(opt, optimizer_.Optimizer):
                raise ValueError(
                    "Unrecognized optimizer: function should return " "subclass of Optimizer. Got %s." % str(opt)
                )
        else:
            raise ValueError(
                "Unrecognized optimizer: should be string, "
                "subclass of Optimizer, instance of "
                "subclass of Optimizer or function with one argument. "
                "Got %s." % str(optimizer)
            )

        # All trainable variables, if specific variables are not specified.
        if variables is None:
            variables = vars_.trainable_variables()

        # Compute gradients.
        gradients = opt.compute_gradients(loss, variables)

        # Optionally add gradient noise.
        if gradient_noise_scale is not None:
            gradients = _add_scaled_noise_to_gradients(gradients, gradient_noise_scale)

        # Multiply some gradients.
        if gradient_multipliers is not None:
            gradients = _multiply_gradients(gradients, gradient_multipliers)

        # Optionally clip gradients by global norm.
        if clip_gradients is not None:
            gradients = _clip_gradients_by_norm(gradients, clip_gradients)

        # Add scalar summary for loss.
        if "loss" in summaries:
            logging_ops.scalar_summary("loss", loss)

        # Add histograms for variables, gradients and gradient norms.
        for gradient, variable in gradients:
            if isinstance(gradient, ops.IndexedSlices):
                grad_values = gradient.values
            else:
                grad_values = gradient

            if grad_values is not None:
                if "gradients" in summaries:
                    logging_ops.histogram_summary(variable.name + "/gradients", grad_values)
                if "gradient_norm" in summaries:
                    logging_ops.histogram_summary(variable.name + "/gradient_norm", clip_ops.global_norm([grad_values]))

        # Create gradient updates.
        grad_updates = opt.apply_gradients(gradients, global_step=global_step, name="train")

        # Ensure the train_tensor computes grad_updates.
        train_tensor = control_flow_ops.with_dependencies([grad_updates], loss)

        return train_tensor

def create_train_op(
    total_loss,
    optimizer,
    global_step=None,
    update_ops=None,
    variables_to_train=None,
    clip_gradient_norm=0,
    summarize_gradients=False,
    gate_gradients=tf_optimizer.Optimizer.GATE_OP,
    aggregation_method=None,
    colocate_gradients_with_ops=False):
  """Creates an `Operation` that evaluates the gradients and returns the loss.

  Args:
    total_loss: A `Tensor` representing the total loss.
    optimizer: A tf.Optimizer to use for computing the gradients.
    global_step: A `Tensor` representing the global step variable. If left as
      `None`, then slim.variables.global_step() is used.
    update_ops: an optional list of updates to execute. Note that the update_ops
      that are used are the union of those update_ops passed to the function and
      the value of slim.ops.GetUpdateOps(). Therefore, if `update_ops` is None,
      then the value of slim.ops.GetUpdateOps() is still used.
    variables_to_train: an optional list of variables to train. If None, it will
      default to all tf.trainable_variables().
    clip_gradient_norm: If greater than 0 then the gradients would be clipped
      by it.
    summarize_gradients: Whether or not add summaries for each gradient.
    gate_gradients: How to gate the computation of gradients. See tf.Optimizer.
    aggregation_method: Specifies the method used to combine gradient terms.
      Valid values are defined in the class `AggregationMethod`.
    colocate_gradients_with_ops: Whether or not to try colocating the gradients
      with the ops that generated them.

  Returns:
    A `Tensor` that when evaluated, computes the gradients and returns the total
      loss value.
  """
  if global_step is None:
    global_step = variables.get_or_create_global_step()

  update_ops = set(update_ops or [])

  # Make sure update_ops are computed before total_loss.
  if update_ops:
    with control_flow_ops.control_dependencies(update_ops):
      barrier = control_flow_ops.no_op(name='update_barrier')
    total_loss = control_flow_ops.with_dependencies([barrier], total_loss)

  if variables_to_train is None:
    # Default to tf.trainable_variables()
    variables_to_train = tf_variables.trainable_variables()
  else:
    # Make sure that variables_to_train are in tf.trainable_variables()
    for v in variables_to_train:
      assert v in tf_variables.trainable_variables()

  assert variables_to_train

  # Create the gradients. Note that apply_gradients adds the gradient
  # computation to the current graph.
  grads = optimizer.compute_gradients(
      total_loss, variables_to_train, gate_gradients=gate_gradients,
      aggregation_method=aggregation_method,
      colocate_gradients_with_ops=colocate_gradients_with_ops)

  # Clip gradients.
  if clip_gradient_norm > 0:
    grads = clip_gradient_norms(grads, clip_gradient_norm)

  # Summarize gradients.
  if summarize_gradients:
    for grad, var in grads:
      if grad is not None:
        if isinstance(grad, ops.IndexedSlices):
          grad_values = grad.values
        else:
          grad_values = grad
        logging_ops.histogram_summary(var.op.name + ':gradient', grad_values)
        logging_ops.histogram_summary(var.op.name + ':gradient_norm',
                                      clip_ops.global_norm([grad_values]))
      else:
        logging.info('Var %s has no gradient', var.op.name)

  # Create gradient updates.
  grad_updates = optimizer.apply_gradients(grads, global_step=global_step)

  # Make sure total_loss is valid.
  total_loss = array_ops.check_numerics(total_loss, 'LossTensor is inf or nan')

  # Ensure the train_tensor computes grad_updates.
  return control_flow_ops.with_dependencies([grad_updates], total_loss)