Don't discard the previous input to OuterSS().

theano/sandbox/cuda/blocksparse.py

@@ -683,7 +683,8 @@ GpuElemwise{mul}(lr, SparseBlockOuterSS) -> SparseBlockOuterSS(..., alpha=lr)
     @opt.local_optimizer([GpuElemwise])
     def local_merge_blocksparse_output(node):
         if (isinstance(node.op, GpuElemwise) and
-            (node.op.scalar_op == scalar.sub or node.scalar_op == scalar.add) and
+            (node.op.scalar_op == scalar.sub or
+             node.scalar_op == scalar.add) and
             node.nin == 2):
             ger = grab_ger(node.inputs[0])
             W = node.inputs[1]
@@ -692,9 +693,12 @@ GpuElemwise{mul}(lr, SparseBlockOuterSS) -> SparseBlockOuterSS(..., alpha=lr)
                 W = node.inputs[0]
             if ger is None:
                 return None
-            alpha = get.inputs[5]
             if node.op.scalar_op == scalar.sub:
-                alpha = -alpha
+                alpha = -ger.inputs[5]
+                W = W - ger.inputs[0]
+            else:
+                alpha = ger.inputs[5]
+                W = W + ger.inputs[0]
             return [sparse_block_outer_ss(*([W] + ger.inputs[1:5] +
                                             [alpha]))]