update docs

docs/modules/dataflow.imgaug.rst

@@ -4,7 +4,7 @@ tensorpack.dataflow.imgaug package
 This package contains Tensorpack's augmentors.
 Note that other image augmentation libraries can be wrapped into Tensorpack's interface as well.
 For example, `imgaug.IAAugmentor <#tensorpack.dataflow.imgaug.IAAugmentor>`_
-and `imgaug.Albumentations <#tensorpack.dataflow.imgaug.Albumentations`_
+and `imgaug.Albumentations <#tensorpack.dataflow.imgaug.Albumentations>`_
 wrap two popular image augmentation libraries.
 
 .. container:: custom-index

examples/FasterRCNN/train.py

@@ -555,7 +555,7 @@ if __name__ == '__main__':
         train_dataflow = get_train_dataflow()
         # This is what's commonly referred to as "epochs"
         total_passes = cfg.TRAIN.LR_SCHEDULE[-1] * 8 / train_dataflow.size()
-        logger.info("Total passes of the training set is: {}".format(total_passes))
+        logger.info("Total passes of the training set is: {:.5g}".format(total_passes))
 
         callbacks = [
             PeriodicCallback(

tensorpack/dataflow/imgaug/external.py

@@ -10,7 +10,7 @@ __all__ = ['IAAugmentor', 'Albumentations']
 
 class IAAugmentor(ImageAugmentor):
     """
-    Wrap an augmentor form the IAA library: https://github.com/aleju/imgaug
+    Wrap an augmentor form the IAA library: https://github.com/aleju/imgaug.
     Both images and coordinates are supported.
 
     Note:
@@ -20,6 +20,19 @@ class IAAugmentor(ImageAugmentor):
         2. Only uint8 images are supported by the IAA library.
 
         3. The IAA library can only produces images of the same shape.
+
+    Example:
+
+    .. code-block:: python
+
+        from tensorpack import imgaug  # this is not the aleju/imgaug library
+        from imgaug import augmentors as iaa  # this is the aleju/imgaug library
+        myaug = imgaug.IAAugmentor(
+            iaa.Sequential([
+                iaa.Sharpen(alpha=(0, 1), lightness=(0.75, 1.5)),
+                iaa.Fliplr(0.5),
+                iaa.Crop(px=(0, 100)),
+            ])
     """
 
     def __init__(self, augmentor):
@@ -48,8 +61,16 @@ class IAAugmentor(ImageAugmentor):
 
 class Albumentations(ImageAugmentor):
     """
-    Wrap an augmentor form the albumentations library: https://github.com/albu/albumentations
+    Wrap an augmentor form the albumentations library: https://github.com/albu/albumentations.
     Coordinate augmentation is not supported by the library.
+
+    Example:
+
+    .. code-block:: python
+
+        from tensorpack import imgaug
+        import albumentations as AB
+        myaug = imgaug.Albumentations(AB.RandomRotate90(p=1))
     """
     def __init__(self, augmentor):
         """

tensorpack/dataflow/parallel.py

@@ -146,6 +146,9 @@ class MultiProcessPrefetchData(ProxyDataFlow):
         3. You can nest like this: ``PrefetchDataZMQ(PrefetchData(df, nr_proc=a), nr_proc=b)``.
            A total of ``a`` instances of ``df`` worker processes will be created.
         4. fork happens in `__init__`. `reset_state()` is a no-op. The worker processes won't get called.
+        5. This DataFlow does support windows. However, Windows requires more strict picklability on processes,
+           which means that some code that's forkable on Linux may not be forkable on Windows. If that happens you'll
+           need to re-organize some part of code that's not forkable.
     """
 
     class _Worker(mp.Process):
@@ -170,9 +173,10 @@ class MultiProcessPrefetchData(ProxyDataFlow):
             nr_prefetch (int): size of the queue to hold prefetched datapoints.
             nr_proc (int): number of processes to use.
         """
+        # https://docs.python.org/3.6/library/multiprocessing.html?highlight=process#the-spawn-and-forkserver-start-methods
         if os.name == 'nt':
-            logger.warn("MultiProcessPrefetchData does support windows. \
-However, windows requires more strict picklability on processes, which may \
+            logger.warn("MultiProcessPrefetchData does support Windows. \
+However, Windows requires more strict picklability on processes, which may \
 lead of failure on some of the code.")
         super(MultiProcessPrefetchData, self).__init__(ds)
         try:
@@ -210,8 +214,7 @@ PrefetchData = MultiProcessPrefetchData
 # TODO renamed to MultiProcessDataFlow{,ZMQ} if separated to a new project
 class PrefetchDataZMQ(_MultiProcessZMQDataFlow):
     """
-    Prefetch data from a DataFlow using multiple processes, with ZeroMQ for
-    communication.
+    Prefetch data from a DataFlow using multiple processes, with ZeroMQ for communication.
     It will fork the calling process of :meth:`reset_state()`,
     and collect datapoints from the given dataflow in each process by ZeroMQ IPC pipe.
 
@@ -237,7 +240,8 @@ class PrefetchDataZMQ(_MultiProcessZMQDataFlow):
            it won't be usable in the forked process. Therefore, do not nest two `PrefetchDataZMQ`.
         5. (Thread-safety) ZMQ is not thread safe. Therefore, do not call :meth:`get_data` of the same dataflow in
            more than 1 threads.
-        6. (For Mac only) A UNIX named pipe will be created in the current directory.
+        6. This dataflow does not support windows. Use `MultiProcessPrefetchData` which works on windows.
+        7. (For Mac only) A UNIX named pipe will be created in the current directory.
            However, certain non-local filesystem such as NFS/GlusterFS/AFS doesn't always support pipes.
            You can change the directory by ``export TENSORPACK_PIPEDIR=/other/dir``.
            In particular, you can use somewhere under '/tmp' which is usually local.

tensorpack/models/batch_norm.py

@@ -103,12 +103,13 @@ def BatchNorm(inputs, axis=None, training=None, momentum=0.9, epsilon=1e-5,
           It uses the aggregated statistics of the whole batch (across all MPI ranks) to normalize.
           Note that on single machine this is significantly slower than the "nccl" implementation.
 
-          This implementation averages the per-GPU E[x] and E[x^2] among GPUs to compute
+          If not None, per-GPU E[x] and E[x^2] among all GPUs are averaged to compute
           global mean & variance. Therefore each GPU needs to have the same batch size.
-          It will match the BatchNorm layer on each GPU by its name (`BatchNorm('name', input)`).
-          If names do not match, the operation will hang.
 
-          This option has no effect when not training.
+          The BatchNorm layer on each GPU needs to use the same name (`BatchNorm('name', input)`), so that
+          statistics can be reduced. If names do not match, this layer will hang.
+
+          This option only has effect in standard training mode.
 
           This option is also known as "Cross-GPU BatchNorm" as mentioned in:
           `MegDet: A Large Mini-Batch Object Detector <https://arxiv.org/abs/1711.07240>`_.