diff --git a/inferno/extensions/containers/graph.py b/inferno/extensions/containers/graph.py
index 0bbf57b0..45e82286 100755
--- a/inferno/extensions/containers/graph.py
+++ b/inferno/extensions/containers/graph.py
@@ -130,7 +130,7 @@ def is_node_in_graph(self, name):
         -------
         bool
         """
-        return name in self.graph.node
+        return name in self.graph.nodes
 
     def is_source_node(self, name):
         """
@@ -187,7 +187,7 @@ def output_nodes(self):
         list
             A list of names (str) of the output nodes.
         """
-        return [name for name, node_attributes in self.graph.node.items()
+        return [name for name, node_attributes in self.graph.nodes.items()
                 if node_attributes.get('is_output_node', False)]
 
     @property
@@ -201,7 +201,7 @@ def input_nodes(self):
         list
             A list of names (str) of the input nodes.
         """
-        return [name for name, node_attributes in self.graph.node.items()
+        return [name for name, node_attributes in self.graph.nodes.items()
                 if node_attributes.get('is_input_node', False)]
 
     @property
diff --git a/inferno/extensions/optimizers/__init__.py b/inferno/extensions/optimizers/__init__.py
index 7235cead..842dd8f9 100755
--- a/inferno/extensions/optimizers/__init__.py
+++ b/inferno/extensions/optimizers/__init__.py
@@ -1,2 +1,3 @@
 from .adam import Adam
-from .annealed_adam import AnnealedAdam
\ No newline at end of file
+from .annealed_adam import AnnealedAdam
+from .ranger import Ranger, RangerQH, RangerVA
diff --git a/inferno/extensions/optimizers/ranger.py b/inferno/extensions/optimizers/ranger.py
new file mode 100644
index 00000000..c01ea0d5
--- /dev/null
+++ b/inferno/extensions/optimizers/ranger.py
@@ -0,0 +1,8 @@
+# easy support for additional ranger optimizers from
+# https://github.com/lessw2020/Ranger-Deep-Learning-Optimizer
+try:
+    from ranger import Ranger, RangerVA, RangerQH
+except ImportError:
+    Ranger = None
+    RangerVA = None
+    RangerQH = None
diff --git a/inferno/io/transform/base.py b/inferno/io/transform/base.py
index 6c23113c..7a63804b 100755
--- a/inferno/io/transform/base.py
+++ b/inferno/io/transform/base.py
@@ -58,7 +58,7 @@ def __call__(self, *tensors, **transform_function_kwargs):
             transformed = self.batch_function(tensors, **transform_function_kwargs)
             return pyu.from_iterable(transformed)
         elif hasattr(self, 'tensor_function'):
-            transformed = [self.tensor_function(tensor, **transform_function_kwargs)
+            transformed = [self._apply_tensor_function(tensor, **transform_function_kwargs)
                            if tensor_index in apply_to else tensor
                            for tensor_index, tensor in enumerate(tensors)]
             return pyu.from_iterable(transformed)
@@ -77,9 +77,17 @@ def __call__(self, *tensors, **transform_function_kwargs):
         else:
             raise NotImplementedError
 
+    # noinspection PyUnresolvedReferences
+    def _apply_tensor_function(self, tensor, **transform_function_kwargs):
+        if isinstance(tensor, list):
+            return [self._apply_tensor_function(tens) for tens in tensor]
+        return self.tensor_function(tensor)
+
     # noinspection PyUnresolvedReferences
     def _apply_image_function(self, tensor, **transform_function_kwargs):
         assert pyu.has_callable_attr(self, 'image_function')
+        if isinstance(tensor, list):
+            return [self._apply_image_function(tens) for tens in tensor]
         # 2D case
         if tensor.ndim == 4:
             return np.array([np.array([self.image_function(image, **transform_function_kwargs)
@@ -106,6 +114,8 @@ def _apply_image_function(self, tensor, **transform_function_kwargs):
     # noinspection PyUnresolvedReferences
     def _apply_volume_function(self, tensor, **transform_function_kwargs):
         assert pyu.has_callable_attr(self, 'volume_function')
+        if isinstance(tensor, list):
+            return [self._apply_volume_function(tens) for tens in tensor]
         # 3D case
         if tensor.ndim == 5:
             # tensor is bczyx
@@ -125,7 +135,7 @@ def _apply_volume_function(self, tensor, **transform_function_kwargs):
             # We're applying the volume function on the volume itself
             return self.volume_function(tensor, **transform_function_kwargs)
         else:
-            raise NotImplementedError
+            raise NotImplementedError("Volume function not implemented for ndim %i" % tensor.ndim)
 
 
 class Compose(object):
diff --git a/inferno/io/transform/image.py b/inferno/io/transform/image.py
index db97992c..77b5a016 100755
--- a/inferno/io/transform/image.py
+++ b/inferno/io/transform/image.py
@@ -596,5 +596,5 @@ def batch_function(self, image):
                 pad_r = image_shape - new_shape - pad_l
                 padding = [(0,0)] + list(zip(pad_l, pad_r))
                 img = np.pad(img, padding, 'constant', constant_values=self.pad_const)
-                seg = np.pad(seg, padding, 'constant', constant_values=self.pad_const)     
-        return img, seg
\ No newline at end of file
+                seg = np.pad(seg, padding, 'constant', constant_values=self.pad_const)
+        return img, seg
diff --git a/inferno/io/transform/volume.py b/inferno/io/transform/volume.py
index 721203d2..8afaade2 100755
--- a/inferno/io/transform/volume.py
+++ b/inferno/io/transform/volume.py
@@ -63,6 +63,7 @@ def volume_function(self, volume):
         return volume
 
 
+# TODO this is obsolete
 class AdditiveRandomNoise3D(Transform):
     """ Add gaussian noise to 3d volume
 
@@ -105,7 +106,7 @@ def __init__(self, sigma, mode='gaussian', **super_kwargs):
         self.sigma = sigma
 
     # TODO check if volume is tensor and use torch functions in that case
-    def volume_function(self, volume):
+    def tensor_function(self, volume):
         volume += np.random.normal(loc=0, scale=self.sigma, size=volume.shape)
         return volume
 
diff --git a/inferno/io/volumetric/lazy_volume_loader.py b/inferno/io/volumetric/lazy_volume_loader.py
index e194a270..b57006b6 100644
--- a/inferno/io/volumetric/lazy_volume_loader.py
+++ b/inferno/io/volumetric/lazy_volume_loader.py
@@ -1,5 +1,7 @@
 import numpy as np
 import os
+import pickle
+from concurrent import futures
 
 # try to load io libraries (h5py and z5py)
 try:
@@ -20,10 +22,39 @@
 from ...utils import python_utils as pyu
 
 
+# TODO support h5py as well
+def filter_base_sequence(input_path, input_key,
+                         window_size, stride,
+                         filter_function, n_threads):
+    with z5py.File(input_path, 'r') as f:
+        ds = f[input_key]
+        shape = list(ds.shape)
+        sequence = vu.slidingwindowslices(shape=shape,
+                                          window_size=window_size,
+                                          strides=stride,
+                                          shuffle=True,
+                                          add_overhanging=True)
+
+        def check_slice(slice_id, slice_):
+            print("Checking slice_id", slice_id)
+            data = ds[slice_]
+            if filter_function(data):
+                return None
+            else:
+                return slice_
+
+        with futures.ThreadPoolExecutor(n_threads) as tp:
+            tasks = [tp.submit(check_slice, slice_id, slice_) for slice_id, slice_ in enumerate(sequence)]
+            filtered_sequence = [t.result() for t in tasks]
+
+        filtered_sequence = [seq for seq in filtered_sequence if seq is not None]
+        return filtered_sequence
+
+
 class LazyVolumeLoaderBase(SyncableDataset):
     def __init__(self, dataset, window_size, stride, downsampling_ratio=None, padding=None,
                  padding_mode='reflect', transforms=None, return_index_spec=False, name=None,
-                 data_slice=None):
+                 data_slice=None, base_sequence=None):
         super(LazyVolumeLoaderBase, self).__init__()
         assert len(window_size) == dataset.ndim, "%i, %i" % (len(window_size), dataset.ndim)
         assert len(stride) == dataset.ndim
@@ -58,7 +89,22 @@ def __init__(self, dataset, window_size, stride, downsampling_ratio=None, paddin
         else:
             raise NotImplementedError
 
-        self.base_sequence = self.make_sliding_windows()
+        if base_sequence is None:
+            self.base_sequence = self.make_sliding_windows()
+        else:
+            self.base_sequence = self.load_base_sequence(base_sequence)
+
+    @staticmethod
+    def load_base_sequence(base_sequence):
+        if isinstance(base_sequence, (list, tuple)):
+            return base_sequence
+        elif isinstance(base_sequence, str):
+            assert os.path.exists(base_sequence)
+            with open(base_sequence, 'rb') as f:
+                base_sequence = pickle.load(f)
+            return base_sequence
+        else:
+            raise ValueError("Unsupported base_sequence format, must be either listlike or str")
 
     def normalize_slice(self, data_slice):
         if data_slice is None:
@@ -185,7 +231,7 @@ def __init__(self, file_impl, path,
             assert os.path.exists(path), path
             self.path = path
         else:
-            raise NotImplementedError
+            raise NotImplementedError("Not implemented for type %s" % type(path))
 
         if isinstance(path_in_file, dict):
             assert name is not None
diff --git a/inferno/io/volumetric/volume.py b/inferno/io/volumetric/volume.py
index f4a7fc93..3ee3ab6c 100755
--- a/inferno/io/volumetric/volume.py
+++ b/inferno/io/volumetric/volume.py
@@ -100,6 +100,7 @@ def pad_volume(self, padding=None):
             assert_(all(isinstance(pad, (int, tuple, list)) for pad in self.padding),\
                 "Expect int or iterable", TypeError)
             self.padding = [[pad, pad] if isinstance(pad, int) else pad for pad in self.padding]
+            print(self.volume.shape)
             self.volume = np.pad(self.volume,
                                  pad_width=self.padding,
                                  mode=self.padding_mode)
@@ -228,7 +229,7 @@ def __init__(self, path, path_in_h5_dataset=None, data_slice=None, transforms=No
         if self.data_slice is not None and slicing_config_for_name.get('is_multichannel', False):
             self.data_slice = (slice(None),) + self.data_slice
 
-        assert 'window_size' in slicing_config_for_name
+        assert 'window_size' in slicing_config_for_name, str(slicing_config_for_name)
         assert 'stride' in slicing_config_for_name
 
         # Read in volume from file (can be hdf5, n5 or zarr)
diff --git a/inferno/io/volumetric/volumetric_utils.py b/inferno/io/volumetric/volumetric_utils.py
index d7f321a0..a33b5ebe 100755
--- a/inferno/io/volumetric/volumetric_utils.py
+++ b/inferno/io/volumetric/volumetric_utils.py
@@ -42,12 +42,13 @@ def dimension_window(start, stop, wsize, stride, dimsize, ds_dim):
     # otherwise predict the whole volume
     if dataslice is not None:
         assert len(dataslice) == dim, "Dataslice must be a tuple with len = data dimension."
-        starts = [sl.start for sl in dataslice]
-        stops  = [sl.stop - wsize for sl, wsize in zip(dataslice, window_size)]
+        starts = [0 if sl.start is None else sl.start for sl in dataslice]
+        stops = [sh - wsize if sl.stop is None else sl.stop - wsize
+                 for sl, wsize, sh in zip(dataslice, window_size, shape)]
     else:
         starts = dim * [0]
-        stops  = [dimsize - wsize if wsize != dimsize else dimsize
-                  for dimsize, wsize in zip(shape, window_size)]
+        stops = [dimsize - wsize if wsize != dimsize else dimsize
+                 for dimsize, wsize in zip(shape, window_size)]
 
     assert all(stp > strt for strt, stp in zip(starts, stops)),\
         "%s, %s" % (str(starts), str(stops))
@@ -128,7 +129,7 @@ def _to_list(x):
     nslices = [_1Dwindow(startmin, startmax, nhoodsiz, st, dsample, datalen, shuffle) if windowspec == 'x'
                else [slice(ws, ws + 1) for ws in _to_list(windowspec)]
                for startmin, startmax, datalen, nhoodsiz, st, windowspec, dsample in zip(startmins, startmaxs, shape,
-                                                                                nhoodsize, stride, window, ds)]
+                                                                                         nhoodsize, stride, window, ds)]
 
     return it.product(*nslices)
 
diff --git a/inferno/trainers/basic.py b/inferno/trainers/basic.py
index c90c8ef5..70b53874 100755
--- a/inferno/trainers/basic.py
+++ b/inferno/trainers/basic.py
@@ -27,6 +27,14 @@
 from .callbacks import Console
 from ..utils.exceptions import assert_, NotSetError, NotTorchModuleError, DeviceError
 
+# NOTE for distributed training, we might also need
+# from apex.parallel import DistributedDataParallel as DDP
+# but I don't know where exactly to put it.
+try:
+    from apex import amp
+except ImportError:
+    amp = None
+
 
 class Trainer(object):
     """A basic trainer.
@@ -126,10 +134,44 @@ def __init__(self, model=None):
         # Print console
         self._console = Console()
 
+        # Train with mixed precision, only works
+        # if we have apex
+        self._mixed_precision = False
+        self._apex_opt_level = 'O1'
+
         # Public
         if model is not None:
             self.model = model
 
+    @property
+    def mixed_precision(self):
+        return self._mixed_precision
+
+    # this needs to be called after model and optimizer are set
+    @mixed_precision.setter
+    def mixed_precision(self, mp):
+        if mp:
+            assert_(amp is not None, "Cannot use mixed precision training without apex library", RuntimeError)
+            assert_(self.model is not None and self._optimizer is not None,
+                    "Model and optimizer need to be set before activating mixed precision", RuntimeError)
+            # in order to support BCE loss
+            amp.register_float_function(torch, 'sigmoid')
+            # For now, we don't allow to set 'keep_batchnorm' and 'loss_scale'
+            self.model, self._optimizer = amp.initialize(self.model, self._optimizer,
+                                                         opt_level=self._apex_opt_level,
+                                                         keep_batchnorm_fp32=None)
+        self._mixed_precision = mp
+
+    @property
+    def apex_opt_level(self):
+        return self._apex_opt_level
+
+    @apex_opt_level.setter
+    def apex_opt_level(self, opt_level):
+        assert_(opt_level in ('O0', 'O1', 'O2', 'O3'),
+                "Invalid optimization level", ValueError)
+        self._apex_opt_level = opt_level
+
     @property
     def console(self):
         """Get the current console."""
@@ -1368,17 +1410,21 @@ def apply_model_and_loss(self, inputs, target, backward=True, mode=None):
             kwargs['trainer'] = self
         if mode == 'train':
             loss = self.criterion(prediction, target, **kwargs) \
-                   if len(target) != 0  else self.criterion(prediction, **kwargs) 
+                   if len(target) != 0 else self.criterion(prediction, **kwargs)
         elif mode == 'eval':
             loss = self.validation_criterion(prediction, target, **kwargs) \
-                   if len(target) != 0  else self.validation_criterion(prediction, **kwargs)
+                   if len(target) != 0 else self.validation_criterion(prediction, **kwargs)
         else:
             raise ValueError
         if backward:
             # Backprop if required
             # retain_graph option is needed for some custom
             # loss functions like malis, False per default
-            loss.backward(retain_graph=self.retain_graph)
+            if self.mixed_precision:
+                with amp.scale_loss(loss, self.optimizer) as scaled_loss:
+                    scaled_loss.backward(retain_graph=self.retain_graph)
+            else:
+                loss.backward(retain_graph=self.retain_graph)
         return prediction, loss
 
     def train_for(self, num_iterations=None, break_callback=None):
@@ -1676,7 +1722,7 @@ def load(self, from_directory=None, best=False, filename=None, map_location=None
             'best_checkpoint.pytorch'.
         filename : str
             Overrides the default filename.
-        device : function, torch.device, string or a dict
+        map_location : function, torch.device, string or a dict
             Specify how to remap storage locations.
 
         Returns
diff --git a/inferno/trainers/callbacks/essentials.py b/inferno/trainers/callbacks/essentials.py
index 704e3831..f62d2cc4 100755
--- a/inferno/trainers/callbacks/essentials.py
+++ b/inferno/trainers/callbacks/essentials.py
@@ -277,9 +277,10 @@ def norm_or_value(self):
     def after_model_and_loss_is_applied(self, **_):
         tu.clip_gradients_(self.trainer.model.parameters(), self.mode, self.norm_or_value)
 
+
 class GarbageCollection(Callback):
     """
-    Callback that triggers garbage collection at the end of every 
+    Callback that triggers garbage collection at the end of every
     training iteration in order to reduce the memory footprint of training
     """
 
diff --git a/inferno/trainers/callbacks/scheduling.py b/inferno/trainers/callbacks/scheduling.py
index 3a1fd347..9efaf478 100644
--- a/inferno/trainers/callbacks/scheduling.py
+++ b/inferno/trainers/callbacks/scheduling.py
@@ -301,9 +301,10 @@ def end_of_validation_run(self, **_):
 
     @staticmethod
     def is_significantly_less_than(x, y, min_relative_delta):
+        eps = 1.e-6
         if x > y:
             return False
-        relative_delta = abs(y - x) / abs(y)
+        relative_delta = abs(y - x) / (abs(y) + eps)
         return relative_delta > min_relative_delta
 
 
diff --git a/inferno/utils/io_utils.py b/inferno/utils/io_utils.py
index 5b5ee6e8..8ef4350a 100755
--- a/inferno/utils/io_utils.py
+++ b/inferno/utils/io_utils.py
@@ -49,7 +49,7 @@ def yaml2dict(path):
         # Forgivable mistake that path is a dict already
         return path
     with open(path, 'r') as f:
-        readict = yaml.load(f)
+        readict = yaml.load(f, Loader=yaml.FullLoader)
     return readict