Separate parse_and_preprocess into two different dataset.map calls, which also keeps tests passing

Author: nealwu

official/resnet/cifar10_main.py

@@ -108,45 +108,38 @@ def parse_record(raw_record):
   # Convert bytes to a vector of uint8 that is record_bytes long.
   record_vector = tf.decode_raw(raw_record, tf.uint8)
 
-  # The first byte represents the label, which we convert from uint8 to int32.
+  # The first byte represents the label, which we convert from uint8 to int32
+  # and then to one-hot.
   label = tf.cast(record_vector[0], tf.int32)
+  label = tf.one_hot(label, _NUM_CLASSES)
 
   # The remaining bytes after the label represent the image, which we reshape
   # from [depth * height * width] to [depth, height, width].
-  depth_major = tf.reshape(record_vector[label_bytes:record_bytes],
-                           [_DEPTH, _HEIGHT, _WIDTH])
+  depth_major = tf.reshape(
+      record_vector[label_bytes:record_bytes], [_DEPTH, _HEIGHT, _WIDTH])
 
   # Convert from [depth, height, width] to [height, width, depth], and cast as
   # float32.
   image = tf.cast(tf.transpose(depth_major, [1, 2, 0]), tf.float32)
 
-  return image, tf.one_hot(label, _NUM_CLASSES)
-
-
-def train_preprocess_fn(image):
-  """Preprocess a single training image of layout [height, width, depth]."""
-  # Resize the image to add four extra pixels on each side.
-  image = tf.image.resize_image_with_crop_or_pad(image, _HEIGHT + 8, _WIDTH + 8)
-
-  # Randomly crop a [_HEIGHT, _WIDTH] section of the image.
-  image = tf.random_crop(image, [_HEIGHT, _WIDTH, _DEPTH])
-
-  # Randomly flip the image horizontally.
-  image = tf.image.random_flip_left_right(image)
+  return image, label
 
-  return image
 
+def preprocess_image(image, is_training):
+  """Preprocess a single image of layout [height, width, depth]."""
+  if is_training:
+    # Resize the image to add four extra pixels on each side.
+    image = tf.image.resize_image_with_crop_or_pad(image, _HEIGHT + 8, _WIDTH + 8)
 
-def parse_and_preprocess(record, is_training):
-  """Parse and preprocess records in the CIFAR-10 dataset."""
-  image, label = parse_record(record)
+    # Randomly crop a [_HEIGHT, _WIDTH] section of the image.
+    image = tf.random_crop(image, [_HEIGHT, _WIDTH, _DEPTH])
 
-  if is_training:
-    image = train_preprocess_fn(image)
+    # Randomly flip the image horizontally.
+    image = tf.image.random_flip_left_right(image)
 
   # Subtract off the mean and divide by the variance of the pixels.
   image = tf.image.per_image_standardization(image)
-  return image, label
+  return image
 
 
 def input_fn(is_training, data_dir, batch_size, num_epochs=1):
@@ -168,8 +161,10 @@ def input_fn(is_training, data_dir, batch_size, num_epochs=1):
     # randomness, while smaller sizes have better performance.
     dataset = dataset.shuffle(buffer_size=_SHUFFLE_BUFFER)
 
+  dataset = dataset.map(parse_record)
   dataset = dataset.map(
-      lambda record: parse_and_preprocess(record, is_training))
+      lambda image, label: (preprocess_image(image, is_training), label))
+
   dataset = dataset.prefetch(2 * batch_size)
 
   # We call repeat after shuffling, rather than before, to prevent separate