Modified IncSubtensor so that it can now perform setting in addition

theano/tensor/basic.py

@@ -2006,6 +2006,9 @@ class SubtensorPrinter:
 pprint.assign(lambda pstate, r: r.owner and isinstance(r.owner.op, Subtensor), SubtensorPrinter())
 
 
+def incsubtensor(x, y, idx_list, inplace=False, set_instead_of_inc=False):
+    the_op = IncSubtensor(idx_list, inplace, set_instead_of_inc)
+    return the_op(x, y)
 
 class IncSubtensor(Op):
     """Increment a subtensor.
@@ -2015,18 +2018,23 @@ class IncSubtensor(Op):
         z[i,j,k] += <something> 
     
     It is used internally to implement the gradient on SubTensor.
+
+    :param set_instead_of_inc: if True set the subtensor to the value instead
+    of incrementing it by that value.
     """
 
-    def __init__(self, idx_list, inplace=False):
+    def __init__(self, idx_list, inplace=False, set_instead_of_inc=False):
         self.idx_list = map(Subtensor.convert, idx_list)
         self.inplace = inplace
         if inplace:
             self.destroy_map = {0: [0]}
+        self.set_instead_of_inc = set_instead_of_inc
 
     def __eq__(self, other):
         return type(self) == type(other) \
                 and self.idx_list == other.idx_list \
-                and self.inplace == other.inplace
+                and self.inplace == other.inplace \
+                and self.set_instead_of_inc == other.set_instead_of_inc
 
     def __hash__(self):
         msg = []
@@ -2042,7 +2050,8 @@ class IncSubtensor(Op):
         #                 if isinstance(entry, slice)
         #                 else entry
         #                 for entry in self.idx_list)
-        return hashtype(self) ^ hash(idx_list) ^ hash(self.inplace)
+        return hashtype(self) ^ hash(idx_list) ^ hash(self.inplace) \
+                        ^ hash(self.set_instead_of_inc)
 
     def __str__(self):
         indices = []
@@ -2055,6 +2064,10 @@ class IncSubtensor(Op):
             msg = 'Inplace'
         else:
             msg = ''
+        if not self.set_instead_of_inc:
+            msg += 'Inc'
+        else:
+            msg += 'Set'
         return  "%s%s{%s}" % (msg,
                 self.__class__.__name__, ", ".join(indices))
 
@@ -2107,10 +2120,17 @@ class IncSubtensor(Op):
         sub_x = x.__getitem__(cdata)
         if sub_x.shape:
             # we've sliced out an N-D tensor with N > 0
+            if not self.set_instead_of_inc:
                 sub_x += y
+            else:
+                #sub_x += -sub_x + y
+                x.__setitem__(cdata, y)
         else:
             # scalar case
+            if not self.set_instead_of_inc:
                 x.__setitem__(cdata, sub_x + y)
+            else:
+                x.__setitem__(cdata, y)
         out[0] = x
 
 def split(x, splits_size, n_splits, axis=0):