refine multigpu code

example_alexnet.py

@@ -55,7 +55,7 @@ def get_model(inputs, is_training):
     y = one_hot(label, 1000)
     cost = tf.nn.softmax_cross_entropy_with_logits(logits, y)
     cost = tf.reduce_mean(cost, name='cross_entropy_loss')
-    tf.add_to_collection(COST_VARS_KEY, cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, cost)
 
     # compute the number of failed samples, for ValidationError to use at test time
     wrong = tf.not_equal(
@@ -64,13 +64,13 @@ def get_model(inputs, is_training):
     nr_wrong = tf.reduce_sum(wrong, name='wrong')
     # monitor training error
     tf.add_to_collection(
-        SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
+        MOVING_SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
 
     # weight decay on all W of fc layers
     wd_cost = tf.mul(1e-4,
                      regularize_cost('fc.*/W', tf.nn.l2_loss),
                      name='regularize_loss')
-    tf.add_to_collection(COST_VARS_KEY, wd_cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, wd_cost)
 
     add_histogram_summary('.*/W')   # monitor histogram of all W
     return [prob, nr_wrong], tf.add_n([wd_cost, cost], name='cost')

example_cifar10.py

@@ -56,7 +56,7 @@ def get_model(inputs, is_training):
     y = one_hot(label, 10)
     cost = tf.nn.softmax_cross_entropy_with_logits(logits, y)
     cost = tf.reduce_mean(cost, name='cross_entropy_loss')
-    tf.add_to_collection(SUMMARY_VARS_KEY, cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, cost)
 
     # compute the number of failed samples, for ValidationError to use at test time
     wrong = tf.not_equal(
@@ -65,13 +65,13 @@ def get_model(inputs, is_training):
     nr_wrong = tf.reduce_sum(wrong, name='wrong')
     # monitor training error
     tf.add_to_collection(
-        SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
+        MOVING_SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
 
     # weight decay on all W of fc layers
     wd_cost = tf.mul(1e-4,
                      regularize_cost('fc.*/W', tf.nn.l2_loss),
                      name='regularize_loss')
-    tf.add_to_collection(SUMMARY_VARS_KEY, wd_cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, wd_cost)
 
     add_histogram_summary('.*/W')   # monitor histogram of all W
     return [prob, nr_wrong], tf.add_n([wd_cost, cost], name='cost')
@@ -154,5 +154,6 @@ if __name__ == '__main__':
             config = get_config()
         if args.load:
             config.session_init = SaverRestore(args.load)
-
+        if args.gpu:
+            config['nr_tower'] = len(args.gpu.split(','))
         start_train(config)

example_mnist.py

@@ -65,7 +65,7 @@ def get_model(inputs, is_training):
     y = one_hot(label, 10)
     cost = tf.nn.softmax_cross_entropy_with_logits(logits, y)
     cost = tf.reduce_mean(cost, name='cross_entropy_loss')
-    tf.add_to_collection(COST_VARS_KEY, cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, cost)
 
     # compute the number of failed samples, for ValidationError to use at test time
     wrong = tf.not_equal(
@@ -74,13 +74,13 @@ def get_model(inputs, is_training):
     nr_wrong = tf.reduce_sum(wrong, name='wrong')
     # monitor training error
     tf.add_to_collection(
-        SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
+        MOVING_SUMMARY_VARS_KEY, tf.reduce_mean(wrong, name='train_error'))
 
     # weight decay on all W of fc layers
     wd_cost = tf.mul(1e-4,
                      regularize_cost('fc.*/W', tf.nn.l2_loss),
                      name='regularize_loss')
-    tf.add_to_collection(COST_VARS_KEY, wd_cost)
+    tf.add_to_collection(MOVING_SUMMARY_VARS_KEY, wd_cost)
 
     add_histogram_summary('.*/W')   # monitor histogram of all W
     return [prob, nr_wrong], tf.add_n([wd_cost, cost], name='cost')
@@ -95,7 +95,7 @@ def get_config():
     dataset_train = BatchData(dataset.Mnist('train'), 128)
     dataset_test = BatchData(dataset.Mnist('test'), 256, remainder=True)
     step_per_epoch = dataset_train.size()
-    step_per_epoch = 30
+    #step_per_epoch = 30
     #dataset_test = FixedSizeData(dataset_test, 20)
 
     sess_config = get_default_sess_config()

tensorpack/train.py

@@ -46,6 +46,7 @@ class TrainConfig(object):
             step_per_epoch: the number of steps (parameter updates) to perform
                 in each epoch. default to dataset.size()
             max_epoch: maximum number of epoch to run training. default to 100
+            nr_tower: int. number of towers. default to 1.
         """
         def assert_type(v, tp):
             assert isinstance(v, tp), v.__class__
@@ -70,21 +71,10 @@ class TrainConfig(object):
         self.step_per_epoch = int(kwargs.pop('step_per_epoch', self.dataset.size()))
         self.max_epoch = int(kwargs.pop('max_epoch', 100))
         assert self.step_per_epoch > 0 and self.max_epoch > 0
+        self.nr_tower = int(kwargs.pop('nr_tower', 1))
         assert len(kwargs) == 0, 'Unknown arguments: {}'.format(str(kwargs.keys()))
 
 def average_gradients(tower_grads):
-  """Calculate the average gradient for each shared variable across all towers.
-
-  Note that this function provides a synchronization point across all towers.
-
-  Args:
-    tower_grads: List of lists of (gradient, variable) tuples. The outer list
-      is over individual gradients. The inner list is over the gradient
-      calculation for each tower.
-  Returns:
-     List of pairs of (gradient, variable) where the gradient has been averaged
-     across all towers.
-  """
   average_grads = []
   for grad_and_vars in zip(*tower_grads):
     # Note that each grad_and_vars looks like the following:
@@ -109,6 +99,10 @@ def average_gradients(tower_grads):
     average_grads.append(grad_and_var)
   return average_grads
 
+def summary_grads(grads):
+    for grad, var in grads:
+        if grad:
+            tf.histogram_summary(var.op.name + '/gradients', grad)
 
 def start_train(config):
     """
@@ -120,6 +114,10 @@ def start_train(config):
     input_queue = config.input_queue
     callbacks = config.callbacks
 
+    tf.add_to_collection(FORWARD_FUNC_KEY, config.get_model_func)
+    for v in input_vars:
+        tf.add_to_collection(INPUT_VARS_KEY, v)
+
     def get_model_inputs():
         model_inputs = input_queue.dequeue()
         for qv, v in zip(model_inputs, input_vars):
@@ -134,40 +132,38 @@ def start_train(config):
     else:
         enqueue_op = input_queue.enqueue_many(input_vars)
 
-    keys_to_maintain = [tf.GraphKeys.SUMMARIES, SUMMARY_VARS_KEY]
-    olds = {}
-    for k in keys_to_maintain:
-        olds[k] = copy.copy(tf.get_collection(k))
-    all_grads = []
-    n_tower = 1
-    for i in range(n_tower):
+    # get gradients to update:
+    logger.info("Training a model of {} tower".format(config.nr_tower))
+    if config.nr_tower > 1:
+        coll_keys = [tf.GraphKeys.SUMMARIES, MOVING_SUMMARY_VARS_KEY]
+        kept_summaries = {}
+        grads = []
+        for i in range(config.nr_tower):
             with tf.device('/gpu:{}'.format(i)):
-            with tf.name_scope('tower{}'.format(i)):
-                for k in keys_to_maintain:
-                    del tf.get_collection(k)[:]
                 model_inputs = get_model_inputs()
                 output_vars, cost_var = config.get_model_func(model_inputs, is_training=True)
+                grads.append(
+                    config.optimizer.compute_gradients(cost_var))
+
+                if i == 0:
                     tf.get_variable_scope().reuse_variables()
+                    for k in coll_keys:
+                        kept_summaries[k] = copy.copy(tf.get_collection(k))
+        for k in coll_keys:  # avoid repeating summary on multiple devices
+            del tf.get_collection(k)[:]
+            tf.get_collection(k).extend(kept_summaries[k])
+        grads = average_gradients(grads)
+    else:
+        model_inputs = get_model_inputs()
+        output_vars, cost_var = config.get_model_func(model_inputs, is_training=True)
         grads = config.optimizer.compute_gradients(cost_var)
-                all_grads.append(grads)
-    for k in keys_to_maintain:
-        tf.get_collection(k).extend(olds[k])
-    grads = average_gradients(all_grads)
-    for grad, var in grads:
-        if grad:
-            tf.histogram_summary(var.op.name + '/gradients', grad)
+    summary_grads(grads)
     avg_maintain_op = summary_moving_average(cost_var)
 
-    # build graph
-    tf.add_to_collection(FORWARD_FUNC_KEY, config.get_model_func)
-    for v in input_vars:
-        tf.add_to_collection(INPUT_VARS_KEY, v)
-    describe_model()
-
-    # train_op = get_train_op(config.optimizer, cost_var)
     with tf.control_dependencies([avg_maintain_op]):
         train_op = config.optimizer.apply_gradients(grads, get_global_step_var())
 
+    describe_model()
     sess = tf.Session(config=config.session_config)
     config.session_init.init(sess)
 

tensorpack/utils/naming.py

@@ -9,8 +9,7 @@ GLOBAL_STEP_VAR_NAME = 'global_step:0'
 SUMMARY_WRITER_COLLECTION_KEY = 'summary_writer'
 
 INPUT_VARS_KEY = 'INPUT_VARIABLES'
-COST_VARS_KEY = 'COST_VARIABLES'        # keep track of each individual cost
-SUMMARY_VARS_KEY = 'SUMMARY_VARIABLES'  # extra variables to summarize during training
+MOVING_SUMMARY_VARS_KEY = 'MOVING_SUMMARY_VARIABLES'  # extra variables to summarize during training
 FORWARD_FUNC_KEY = 'FORWARD_FUNCTION'
 
 # export all upper case variables

tensorpack/utils/summary.py

@@ -31,7 +31,6 @@ def add_activation_summary(x, name=None):
         name = x.name
     tf.histogram_summary(name + '/activations', x)
     tf.scalar_summary(name + '/sparsity', tf.nn.zero_fraction(x))
-    # TODO avoid repeating activations on multiple GPUs
 
 def add_histogram_summary(regex):
     """
@@ -46,15 +45,14 @@ def add_histogram_summary(regex):
 
 def summary_moving_average(cost_var):
     """ Create a MovingAverage op and summary for all variables in
-        COST_VARS_KEY, SUMMARY_VARS_KEY, as well as the argument
+        MOVING_SUMMARY_VARS_KEY, as well as the argument
         Return a op to maintain these average
     """
     global_step_var = tf.get_default_graph().get_tensor_by_name(GLOBAL_STEP_VAR_NAME)
     averager = tf.train.ExponentialMovingAverage(
         0.99, num_updates=global_step_var, name='moving_averages')
     vars_to_summary = [cost_var] + \
-            tf.get_collection(SUMMARY_VARS_KEY) + \
-            tf.get_collection(COST_VARS_KEY)
+            tf.get_collection(MOVING_SUMMARY_VARS_KEY)
     avg_maintain_op = averager.apply(vars_to_summary)
     for idx, c in enumerate(vars_to_summary):
         name = c.op.name