random_projection elements are now in [.5, 1.5] instead of [0, 1] to avoid two small coefficients.

theano/tensor/basic.py

@@ -3588,8 +3588,10 @@ def verify_grad(op, pt, n_tests=2, rng=None, eps=None, tol=None, mode=None, cast
 
         o_fn = function(tensor_pt, o_output)
         o_fn_out = o_fn(*[p.copy() for p in pt])
-        
-        random_projection = rng.rand(*o_fn_out.shape)
+
+        # random_projection should not have elements too small,
+        # otherwise too much precision is lost in numerical gradient
+        random_projection = rng.rand(*o_fn_out.shape) + 0.5
         if cast_to_output_type:
             random_projection = numpy.array(random_projection,
                                             dtype=o_output.dtype)