fixed determinism issues in scan

theano/__init__.py

@@ -88,7 +88,7 @@ from printing import \
 import scan_module
 from scan_module import scan, map, reduce, foldl, foldr, clone
 
-from updates import Updates
+from updates import OrderedUpdates
 
 import tensor
 import scalar

theano/sandbox/scan.py

@@ -17,10 +17,11 @@ import numpy
 from theano.compile import SharedVariable, function
 from theano import compile
 from theano import gof
+from theano.gof.python25 import OrderedDict
 from theano.tensor import opt
 from theano import tensor
 from theano import config
-from theano.updates import Updates
+from theano.updates import OrderedUpdates
 
 
 from theano.scan_module import scan_op
@@ -147,7 +148,7 @@ def scan(fn,
     n_seqs = len(seqs)
     n_outs = len(outs_info)
 
-    return_steps = {}
+    return_steps = OrderedDict()
     # wrap outputs info in a dictionary if they are not already in one
     for i in xrange(n_outs):
         if outs_info[i] is not None:
@@ -242,7 +243,7 @@ def scan(fn,
     mit_sot_inner_inputs = []
     mit_sot_inner_slices = []
     mit_sot_inner_outputs = []
-    mit_sot_return_steps = {}
+    mit_sot_return_steps = OrderedDict()
     mit_sot_tap_array = []
     mit_sot_rightOrder = []
 
@@ -251,7 +252,7 @@ def scan(fn,
     sit_sot_inner_inputs = []
     sit_sot_inner_slices = []
     sit_sot_inner_outputs = []
-    sit_sot_return_steps = {}
+    sit_sot_return_steps = OrderedDict()
     sit_sot_rightOrder = []
     nit_sot_steps = []
     # go through outputs picking up time slices as needed
@@ -398,7 +399,8 @@ def scan(fn,
                       not isinstance(arg, tensor.Constant))]
     # when we apply the lambda expression we get a mixture of update rules
     # and outputs that needs to be separated
-    condition, outputs, updates = scan_utils.get_updates_and_outputs(fn(*args))
+    lambda_result = fn(*args)
+    condition, outputs, updates = scan_utils.get_updates_and_outputs(lambda_result)
     if condition is not None:
         as_while = True
     else:
@@ -464,6 +466,11 @@ def scan(fn,
     dummy_outs = outputs
     if condition is not None:
         dummy_outs.append(condition)
+
+    # If we use a regular dict here, the results are non-deterministic
+    assert isinstance(updates, (list, tuple)) or (isinstance(updates, dict) and \
+            'Ordered' in str(type(updates)))
+
     dummy_f = function(dummy_args,
                        dummy_outs,
                        updates=updates,
@@ -508,7 +515,7 @@ def scan(fn,
             sit_sot_inner_outputs.append(outputs[i])
 
     ## Step 5.3 Outputs that correspond to update rules of shared variables
-    givens = {}
+    givens = OrderedDict()
     n_shared_outs = 0
     shared_scan_inputs = []
     shared_inner_inputs = []
@@ -527,7 +534,7 @@ def scan(fn,
     ## Step 5.4 Outputs with no taps used in the input
     n_nit_sot = 0
     nit_sot_inner_outputs = []
-    nit_sot_return_steps = {}
+    nit_sot_return_steps = OrderedDict()
     nit_sot_rightOrder = []
     for i, out in enumerate(outs_info):
         if not 'taps' in out:
@@ -582,7 +589,7 @@ def scan(fn,
                   shared_inner_outputs)
     if condition is not None:
         inner_outs.append(condition)
-    new_givens = {}
+    new_givens = OrderedDict()
     for w, w_copy in givens.iteritems():
         new_givens[w] = w.type.filter_variable(w_copy)
 
@@ -593,7 +600,7 @@ def scan(fn,
     ##
 
     tap_array = mit_sot_tap_array + [[-1] for x in xrange(n_sit_sot)]
-    info = {}
+    info = OrderedDict()
 
     info['tap_array'] = tap_array
     info['n_seqs'] = n_seqs
@@ -607,7 +614,7 @@ def scan(fn,
     info['truncate_gradient'] = -1
     info['name'] = name
     info['mode'] = mode
-    info['destroy_map'] = {}
+    info['destroy_map'] = OrderedDict()
     info['inplace'] = False
     info['gpu'] = False
     info['as_while'] = as_while
@@ -641,7 +648,7 @@ def scan(fn,
     ###         and so on ...
     ##
 
-    update_map = Updates()
+    update_map = OrderedUpdates()
 
     offset = n_mit_mot
     offsets = [abs(numpy.min(x)) for x in mit_sot_tap_array]
@@ -675,4 +682,5 @@ 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))
     return (scan_out_list, update_map)

theano/scan_module/scan.py

@@ -52,8 +52,9 @@ from theano import gof
 from theano.tensor import opt
 from theano import tensor
 from theano import config
-from theano.updates import Updates
+from theano.updates import OrderedUpdates
 from theano.compile import ops
+from theano.gof.python25 import OrderedDict
 
 
 import scan_op
@@ -376,11 +377,11 @@ def scan(fn,
     n_seqs = len(seqs)
     n_outs = len(outs_info)
 
-    return_steps = {}
+    return_steps = OrderedDict()
     # wrap sequences in a dictionary if they are not already dictionaries
     for i in xrange(n_seqs):
         if not isinstance(seqs[i], dict):
-            seqs[i] = dict(input=seqs[i], taps=[0])
+            seqs[i] = OrderedDict([('input', seqs[i]), ('taps', [0])])
         elif seqs[i].get('taps', None):
             seqs[i]['taps'] = wrap_into_list(seqs[i]['taps'])
         elif seqs[i].get('taps', True) is None:
@@ -402,7 +403,7 @@ def scan(fn,
 
             if not isinstance(outs_info[i], dict):
                 # by default any output has a tap value of -1
-                outs_info[i] = dict(initial=outs_info[i], taps=[-1])
+                outs_info[i] = OrderedDict([('initial', outs_info[i]), ('taps', [-1])])
             elif (not outs_info[i].get('initial', None) and
                     outs_info[i].get('taps', None)):
                 # ^ no initial state but taps provided
@@ -421,8 +422,8 @@ def scan(fn,
                 outs_info[i]['taps'] = [-1]
         else:
             # if a None is provided as the output info we replace it
-            # with an empty dict() to simplify handling
-            outs_info[i] = dict()
+            # with an empty OrdereDict() to simplify handling
+            outs_info[i] = OrderedDict()
 
     ##
     ###   Step 2. Generate inputs and outputs of the inner functions
@@ -565,7 +566,7 @@ def scan(fn,
     mit_sot_inner_inputs = []
     mit_sot_inner_slices = []
     mit_sot_inner_outputs = []
-    mit_sot_return_steps = {}
+    mit_sot_return_steps = OrderedDict()
     mit_sot_tap_array = []
     mit_sot_rightOrder = []
 
@@ -574,7 +575,7 @@ def scan(fn,
     sit_sot_inner_inputs = []
     sit_sot_inner_slices = []
     sit_sot_inner_outputs = []
-    sit_sot_return_steps = {}
+    sit_sot_return_steps = OrderedDict()
     sit_sot_rightOrder = []
 
     # go through outputs picking up time slices as needed
@@ -777,7 +778,7 @@ def scan(fn,
     # as non sequences at the end of our args
     fake_nonseqs = [x.type() for x in non_seqs]
     fake_outputs = scan_utils.clone(outputs,
-                                    replace=dict(zip(non_seqs,
+                                    replace=OrderedDict(zip(non_seqs,
                                                      fake_nonseqs)))
     all_inputs = itertools.ifilter(
         lambda x: (isinstance(x, gof.Variable) and
@@ -825,7 +826,7 @@ def scan(fn,
         n_outs = len(dummy_f.maker.outputs)
         if as_while:
             n_outs = n_outs - 1
-        outs_info = [dict() for x in xrange(n_outs)]
+        outs_info = [OrderedDict() for x in xrange(n_outs)]
 
     ## Step 5.1 Outputs with taps different then -1
 
@@ -839,7 +840,7 @@ def scan(fn,
             sit_sot_inner_outputs.append(outputs[i])
 
     ## Step 5.3 Outputs that correspond to update rules of shared variables
-    givens = {}
+    givens = OrderedDict()
     n_shared_outs = 0
     shared_scan_inputs = []
     shared_inner_inputs = []
@@ -879,7 +880,7 @@ def scan(fn,
     ## Step 5.4 Outputs with no taps used in the input
     n_nit_sot = 0
     nit_sot_inner_outputs = []
-    nit_sot_return_steps = {}
+    nit_sot_return_steps = OrderedDict()
     nit_sot_rightOrder = []
     for i, out in enumerate(outs_info):
         if not 'taps' in out:
@@ -902,7 +903,7 @@ def scan(fn,
                          if (not isinstance(arg, SharedVariable) and
                              not isinstance(arg, tensor.Constant))]
 
-    givens.update(dict(zip(other_scan_args, other_inner_args)))
+    givens.update(OrderedDict(zip(other_scan_args, other_inner_args)))
     other_shared_scan_args = [arg.variable for arg
                         in dummy_f.maker.expanded_inputs
                         if (isinstance(arg.variable, SharedVariable) and
@@ -911,7 +912,7 @@ def scan(fn,
                         in dummy_f.maker.expanded_inputs
                         if (isinstance(arg.variable, SharedVariable) and
                             not arg.update)]
-    givens.update(dict(zip(other_shared_scan_args,
+    givens.update(OrdereDict(zip(other_shared_scan_args,
                            other_shared_inner_args)))
 
     ##
@@ -943,7 +944,7 @@ def scan(fn,
         # replace w with w_copy, where w is CudaNdarray
         # and w_copy is TensorType. This is caused because shared
         # variables are put on GPU right aways >:| ,
-        new_givens = {}
+        new_givens = OrderedDict()
 
         for w, w_copy in givens.iteritems():
             if (isinstance(w.type, cuda.CudaNdarrayType)
@@ -962,7 +963,7 @@ def scan(fn,
     ##
 
     tap_array = mit_sot_tap_array + [[-1] for x in xrange(n_sit_sot)]
-    info = {}
+    info = OrderedDict()
 
     info['tap_array'] = tap_array
     info['n_seqs'] = n_seqs
@@ -976,7 +977,7 @@ def scan(fn,
     info['truncate_gradient'] = truncate_gradient
     info['name'] = name
     info['mode'] = mode
-    info['destroy_map'] = {}
+    info['destroy_map'] = OrderedDict()
     info['gpu'] = False
     info['as_while'] = as_while
     info['profile'] = profile
@@ -1012,7 +1013,7 @@ def scan(fn,
     ###         and so on ...
     ##
 
-    update_map = Updates()
+    update_map = OrderedUpdates()
 
     def remove_dimensions(outs, steps_return, offsets=None):
         out_ls = []

theano/scan_module/scan_utils.py

@@ -23,7 +23,7 @@ import theano
 from theano.compile.pfunc import rebuild_collect_shared
 from theano import gof
 from theano import tensor, scalar
-from theano.gof.python25 import all
+from theano.gof.python25 import all, OrderedDict
 from theano.tensor.basic import get_constant_value
 
 
@@ -181,12 +181,17 @@ def clone(output,
 
 def get_updates_and_outputs(ls):
     """
-    This function tries to recognize the updates dictionary, the
+    This function tries to recognize the updates OrderedDict, the
     list of outputs and the stopping condition returned by the
     lambda expression and arrange them in a predefined order
 
+    WRITEME: what is the type of ls? how is it formatted?
+            if it's not in the predefined order already, how does
+            this function know how to put it in that order?
 
     """
+
+
     def is_outputs(elem):
         if (isinstance(elem, (list, tuple)) and
             all([isinstance(x, theano.Variable) for x in elem])):
@@ -197,6 +202,8 @@ def get_updates_and_outputs(ls):
 
     def is_updates(elem):
         if isinstance(elem, dict):
+            # Make sure the updates will be applied in a deterministic order
+            assert 'Ordered' in str(type(elem))
             return True
         # Dictionaries can be given as lists of tuples
         if (isinstance(elem, (list, tuple)) and
@@ -242,10 +249,11 @@ def get_updates_and_outputs(ls):
                 'values, you can use `tensor.constant` to turn them into '
                  'Theano variables.')
 
+
     if is_outputs(ls):
-        return None, _list(ls), {}
+        return None, _list(ls), OrderedDict()
     if is_updates(ls):
-        return None, [], dict(ls)
+        return None, [], OrderedDict(ls)
     error_msg = ('Scan cannot parse the return value of your lambda '
                  'expression, which is: %s' % (ls,))
     if not isinstance(ls, (list, tuple)):
@@ -258,16 +266,16 @@ def get_updates_and_outputs(ls):
     if len(ls) == 2:
         if is_outputs(ls[0]):
             if is_updates(ls[1]):
-                return (None, _list(ls[0]), dict(ls[1]))
+                return (None, _list(ls[0]), OrderedDict(ls[1]))
             elif is_condition(ls[1]):
-                return (ls[1].condition, _list(ls[0]), {})
+                return (ls[1].condition, _list(ls[0]), OrderedDict())
             else:
                 raise ValueError(error_msg)
         elif is_updates(ls[0]):
             if is_outputs(ls[1]):
                 raise ValueError(deprecation_msg)
             elif is_condition(ls[1]):
-                return (ls[1].condition, [], dict(ls[0]))
+                return (ls[1].condition, [], OrderedDict(ls[0]))
             else:
                 raise ValueError(error_msg)
         else:
@@ -276,7 +284,7 @@ def get_updates_and_outputs(ls):
         if is_outputs(ls[0]):
             if is_updates(ls[1]):
                 if is_condition(ls[2]):
-                    return (ls[2].condition, _list(ls[0]), dict(ls[1]))
+                    return (ls[2].condition, _list(ls[0]), OrderedDict(ls[1]))
                 else:
                     raise ValueError(error_msg)
             else:

theano/updates.py

@@ -8,23 +8,25 @@ __contact__ = "theano-dev <theano-dev@googlegroups.com>"
 
 __docformat__ = "restructuredtext en"
 
+from theano.gof.python25 import OrderedDict
+
 from theano.compile.sharedvalue import SharedVariable
 import logging
 logger = logging.getLogger('theano.updates')
 
-
-class Updates(dict):
+# 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.
 
     This mapping supports the use of the "+" operator for the union of updates.
     """
     def __init__(self, *key, **kwargs):
-        ret = super(Updates, self).__init__(*key, **kwargs)
+        ret = super(OrderedUpdates, self).__init__(*key, **kwargs)
         for key in self:
             if not isinstance(key, SharedVariable):
                 raise TypeError(
-                    'Updates keys must inherit from SharedVariable',
+                    'OrderedUpdates keys must inherit from SharedVariable',
                     key)
         return ret
 
@@ -38,9 +40,9 @@ class Updates(dict):
             # value. Should it be cast to a GPU value right away?  Should
             # literals be transformed into constants immediately?
 
-            return super(Updates, self).__setitem__(key, value)
+            return super(OrderedUpdates, self).__setitem__(key, value)
         else:
-            raise TypeError('Updates keys must inherit from SharedVariable',
+            raise TypeError('OrderedUpdates keys must inherit from SharedVariable',
                     key)
 
     def update(self, other):
@@ -52,13 +54,13 @@ class Updates(dict):
             self[key] = val  # __setitem__ does type-checking
 
     def __add__(self, other):
-        rval = Updates()
+        rval = OrderedUpdates()
         rval.update(self)
         rval.update(other)
         return rval
 
     def __radd__(other, self):
-        rval = Updates()
+        rval = OrderedUpdates()
         rval.update(other)
         rval.update(self)
         return rval