Merge pull request #1100 from delallea/determinism

theano/sandbox/scan.py

@@ -167,7 +167,8 @@ def scan(fn,
                 # ^ initial state but taps not provided
                 if 'taps' in outs_info[i]:
                     # ^ explicitly provided a None for taps
-                    _logger.warning('Output %s ( index %d) has a memory '
+                    _logger.warning(
+                            'Output %s (index %d) has a memory '
                             'buffer but taps is explicitly set to None ',
                             getattr(outs_info[i]['membuf'], 'name', 'None'),
                             i)
@@ -213,7 +214,7 @@ def scan(fn,
 
         nw_slice = _seq_val_slice.type()
         if seq.name:
-            nw_slice.name=seq.name + '[t]'
+            nw_slice.name = seq.name + '[t]'
         scan_seqs.append(_seq_val)
         inner_seqs.append(nw_slice)
         inner_slices.append(actual_slice)
@@ -354,7 +355,6 @@ def scan(fn,
         else:
             pass
 
-
     # Re-order args
     max_mit_sot = numpy.max([-1] + mit_sot_rightOrder) + 1
     max_sit_sot = numpy.max([-1] + sit_sot_rightOrder) + 1
@@ -401,7 +401,8 @@ def scan(fn,
     # when we apply the lambda expression we get a mixture of update rules
     # and outputs that needs to be separated
     lambda_result = fn(*args)
-    condition, outputs, updates = scan_utils.get_updates_and_outputs(lambda_result)
+    condition, outputs, updates = scan_utils.get_updates_and_outputs(
+                                                                lambda_result)
     if condition is not None:
         as_while = True
     else:
@@ -685,5 +686,5 @@ def scan(fn,
     elif len(scan_out_list) == 0:
         scan_out_list = None
 
-    assert isinstance(update_map, dict) and 'Ordered' in str(type(update_map))
+    assert isinstance(update_map, OrderedDict)
     return (scan_out_list, update_map)

theano/updates.py

@@ -16,7 +16,8 @@ logger = logging.getLogger('theano.updates')
 import warnings
 
 
-# Must be an OrderedDict or updates will be applied in a non-deterministic order
+# Must be an OrderedDict or updates will be applied in a non-deterministic
+# order.
 class OrderedUpdates(OrderedDict):
     """
     Dict-like mapping from SharedVariable keys to their new values.
@@ -24,13 +25,20 @@ class OrderedUpdates(OrderedDict):
     This mapping supports the use of the "+" operator for the union of updates.
     """
     def __init__(self, *key, **kwargs):
-        ret = super(OrderedUpdates, self).__init__(*key, **kwargs)
+        if (len(key) >= 1 and
+            isinstance(key[0], dict) and
+            len(key[0]) > 1 and
+            not isinstance(key[0], OrderedDict)):
+            # Warn when using as input a non-ordered dictionary.
+            warnings.warn('Initializing an `OrderedUpdates` from a '
+                          'non-ordered dictionary with 2+ elements could '
+                          'make your code non-deterministic')
+        super(OrderedUpdates, self).__init__(*key, **kwargs)
         for key in self:
             if not isinstance(key, SharedVariable):
                 raise TypeError(
                     'OrderedUpdates keys must inherit from SharedVariable',
                     key)
-        return ret
 
     def __setitem__(self, key, value):
         if isinstance(key, SharedVariable):
@@ -44,13 +52,20 @@ class OrderedUpdates(OrderedDict):
 
             return super(OrderedUpdates, self).__setitem__(key, value)
         else:
-            raise TypeError('OrderedUpdates keys must inherit from SharedVariable',
-                    key)
+            raise TypeError('OrderedUpdates keys must inherit from '
+                            'SharedVariable', key)
 
     def update(self, other=None):
         if other is None:
             return
-        for key, val in dict(other).iteritems():
+        if (isinstance(other, dict) and
+            len(other) > 1 and
+            not isinstance(other, OrderedDict)):
+            # Warn about non-determinism.
+            warnings.warn('Updating an `OrderedUpdates` with a '
+                          'non-ordered dictionary with 2+ elements could '
+                          'make your code non-deterministic')
+        for key, val in OrderedDict(other).iteritems():
             if key in self:
                 if self[key] == val:
                     continue
@@ -69,6 +84,7 @@ class OrderedUpdates(OrderedDict):
         rval.update(self)
         return rval
 
+
 def Updates(*key, **kwargs):
     warnings.warn("Updates is deprecated. Switch to OrderedUpdates.")
     return OrderedUpdates(*key, **kwargs)