Add new subtensor helper make_constant and use it to fix a bug in local_subtensor_merge.

theano/tensor/opt.py

@@ -25,7 +25,8 @@ from theano.gof.utils import MethodNotDefined
 from theano.configparser import config
 from theano.tensor.elemwise import Elemwise, DimShuffle
 from theano.tensor.subtensor import (get_idx_list, get_canonical_form_slice,
-                                     Subtensor, IncSubtensor, AdvancedIncSubtensor1)
+                                     Subtensor, IncSubtensor, make_constant,
+                                     AdvancedIncSubtensor1)
 from theano import scalar
 from theano.tensor import basic as T
 from theano import compile  # to register the optimizer built by this file
@@ -1955,6 +1956,7 @@ def local_subtensor_merge(node):
             else:
                 merged_slices += slices1[pos_1:]
 
+            merged_slices = make_constant(merged_slices)
             subtens = Subtensor(merged_slices)
             sl_ins = Subtensor.collapse(
                 merged_slices,

theano/tensor/subtensor.py

@@ -47,6 +47,23 @@ class AdvancedIndexingError(TypeError):
 # Helpful functions to deal with Subtensor and IncSubtensor
 ##########
 
+def make_constant(args):
+    """
+    Convert python litterals to theano constants in subtensor arguments.
+    """
+    def conv(a):
+            if a is None:
+                return a
+            elif isinstance(a, slice):
+                return slice(conv(a.start),
+                             conv(a.stop),
+                             conv(a.step))
+            elif isinstance(a, (int, long, numpy.integer)):
+                return scal.ScalarConstant(scal.int64, a)
+            else:
+                return a
+    return tuple(map(conv, args))
+
 def get_idx_list(inputs, idx_list):
     '''
     Given a list of inputs to the subtensor and its idx_list reorders

theano/tensor/var.py

@@ -4,8 +4,7 @@ import numpy
 
 import theano
 from theano.compat import all, PY3
-from theano.scalar import (ComplexError, IntegerDivisionError,
-                           ScalarConstant, int64)
+from theano.scalar import ComplexError, IntegerDivisionError
 from theano.gof import Constant, Variable
 from theano.gof.utils import hashtype
 from theano.tensor.utils import hash_from_ndarray
@@ -350,18 +349,7 @@ class _tensor_py_operators:
         if not isinstance(args, tuple):
             args = args,
         # Convert python literals to theano constants
-        def conv(a):
-            if a is None:
-                return a
-            elif isinstance(a, slice):
-                return slice(conv(a.start),
-                             conv(a.stop),
-                             conv(a.step))
-            elif isinstance(a, (int, long, numpy.integer)):
-                return ScalarConstant(int64, a)
-            else:
-                return a
-        args = tuple(map(conv, args))
+        args = theano.tensor.subtensor.make_constant(args)
         # Determine if advanced indexing is needed or not
         # The logic is already in Subtensor.convert: if it succeeds,
         # standard indexing is used; if it fails with