fixed flatten to work for scalars

theano/tensor/basic.py

@@ -1819,7 +1819,7 @@ class Flatten(Op):
         return hash(type(self))^hash(self.outdim)
     def make_node(self, x):
         t_x = as_tensor(x)
-        if self.outdim < 1 or self.outdim > x.ndim:
+        if self.outdim < 1 or (x.ndim and self.outdim > x.ndim):
             raise ValueError('invalid output ndimensions(%i) for tensor of rank %i' %(self.outdim, t_x.ndim))
         return gof.Apply(self, [t_x], [tensor(x.type.dtype, (False,)*self.outdim)])
     def perform(self, node, (x,), (out,)):

theano/tensor/tests/test_basic.py

@@ -1631,6 +1631,18 @@ def test_flatten_outdimNone():
 
     tensor.verify_grad(None, Flatten(), [a_val])
 
+def test_flatten_scalar():
+    a = dscalar()
+    c = flatten(a)
+    f = function([a], c, mode='FAST_COMPILE')
+    a_val = numpy.asarray(3.0, dtype='float64')
+    c_val = numpy.asarray([3.0], dtype='float64')
+    assert numpy.all(f(a_val)==c_val)
+    f = function([a], c, mode='FAST_RUN')
+    assert numpy.all(f(a_val)==c_val)
+
+    #tensor.verify_grad(None, Flatten(), [a_val]) #TODO: fix verify_grd to work on scalars
+
 def test_flatten_outdim1():
     a = dmatrix()
     c = flatten(a, 1)