Make sure to disable C code in CAReduceDtype if the accumulator is in float16.

theano/gof/opt.py

@@ -1288,7 +1288,6 @@ class PatternSub(LocalOptimizer):
                     return pattern.clone()
             p = self.out_pattern
             new = build(p, u)
-            # print "PatternSub matched:", new
             return [new]
         else:
             return False

theano/tensor/elemwise.py

@@ -1467,6 +1467,8 @@ class CAReduce(Op):
         odtype = output.type.dtype_specs()[1]
 
         if hasattr(self, 'acc_dtype') and self.acc_dtype is not None:
+            if self.acc_dtype == 'float16':
+                raise theano.gof.utils.MethodNotDefined("no c_code for float16")
             acc_type = TensorType(
                 broadcastable=node.outputs[0].broadcastable,
                 dtype=self.acc_dtype)
@@ -1632,7 +1634,7 @@ for(int i=0;i<PyArray_NDIM(%(iname)s);i++){
         return ['<vector>', '<algorithm>']
 
     def c_code_cache_version_apply(self, node):
-        version = [5]  # the version corresponding to the c code in this Op
+        version = (6,)  # the version corresponding to the c code in this Op
 
         # now we insert versions for the ops on which we depend...
         scalar_node = Apply(