For scalar that have nin=-1 cache the builded ufunc in the node.tag

theano/tensor/elemwise.py

@@ -7,6 +7,7 @@ import numpy
 import theano
 from theano import gof
 from theano.compat import izip
+from theano.compat import get_unbound_function
 from six import iteritems
 from six.moves import xrange
 from theano.gof import Apply, Op, OpenMPOp
@@ -506,6 +507,9 @@ class Elemwise(OpenMPOp):
         if nfunc_spec:
             self.nfunc = getattr(numpy, nfunc_spec[0])
         elif scalar_op.nin > 0 and scalar_op.nin < 32:
+            # NumPy ufunc support only up to 31 inputs.
+            # But our c code support more.
+            # when nin == -1, we will build the ufunc in the make_thunk.
             self.ufunc = numpy.frompyfunc(scalar_op.impl, scalar_op.nin,
                                           scalar_op.nout)
 
@@ -792,6 +796,20 @@ class Elemwise(OpenMPOp):
 
         return ret
 
+    def make_thunk(self, node, storage_map, compute_map, no_recycling):
+        node_ = node
+        if self.ufunc is None and self.scalar_op.nin == -1:
+            node_ = copy(node)
+            assert node.op is node_.op
+            ufunc = numpy.frompyfunc(self.scalar_op.impl,
+                                     len(node.inputs),
+                                     self.scalar_op.nout)
+            node_.op.ufunc = ufunc
+
+        return super(Elemwise, node_.op).make_thunk(node_, storage_map,
+                                                    compute_map, no_recycling)
+
+
     def perform(self, node, inputs, output_storage):
         if len(node.inputs) >= 32:
             # Some versions of NumPy will segfault, other will raise a
@@ -859,9 +877,11 @@ class Elemwise(OpenMPOp):
         else:
             # the second calling form is used because in certain versions of
             # numpy the first (faster) version leads to segfaults
-            ufunc = (self.ufunc or
-                     numpy.frompyfunc(self.scalar_op.impl, len(inputs),
-                                      self.scalar_op.nout))
+            if self.ufunc:
+                ufunc = self.ufunc
+            else:
+                ufunc = node.tag.ufunc
+
             nout = ufunc.nout
 
         variables = ufunc(*ufunc_args, **ufunc_kwargs)
@@ -1234,6 +1254,9 @@ class Elemwise(OpenMPOp):
         """
         return node.outputs[0].ndim == 0
 
+theano.compile.debugmode.default_make_thunk.append(
+    get_unbound_function(Elemwise.make_thunk))
+
 # def elemwise_to_scal(fgraph):
 # TODO: why is this commented out? should it be removed?
 #       it has needed maintenance despite being commented