Fixed gh-356: dtype of tensor.sum()

theano/tensor/basic.py

@@ -1389,8 +1389,8 @@ class _tensor_py_operators:
     def __rdot__(right, left):
         return dot(left, right)
 
-    def sum(self, axis=None):
-        return elemwise.Sum(axis)(self)
+    def sum(self, *args, **kw):
+        return sum(self, *args, **kw)
 
     def norm(self, L, axis=None):
         if L==0:
@@ -2550,13 +2550,21 @@ def tensor_copy(a):
     """Create a duplicate of `a` (with duplicated storage)"""
 pprint.assign(tensor_copy, printing.IgnorePrinter())
 
+
 @constructor
-def sum(input, axis = None):
-    """WRITEME"""
-    return elemwise.Sum(axis)(input)
+def sum(input, axis=None, dtype=None):
+    """
+    Sum a tensor along the given axis(es).
+
+    For full documentation see ``tensor.elemwise.Sum``.
+    In particular please pay attention to the important warning when using
+    a custom dtype.
+    """
+    return elemwise.Sum(axis=axis, dtype=dtype)(input)
 
 pprint.assign(Sum(), printing.FunctionPrinter('sum'))
 
+
 @constructor
 def prod(input, axis = None):
     """WRITEME"""

theano/tensor/elemwise.py

@@ -1003,7 +1003,7 @@ class CAReduce(Op):
     subtract, divide or power).
     """
 
-    def __init__(self, scalar_op, axis = None):
+    def __init__(self, scalar_op, axis=None):
         """
         Usage: CAReduce(scalar_op, axis = None)
 
@@ -1074,9 +1074,10 @@ class CAReduce(Op):
             op = self.__class__(self.scalar_op, axis)
         else:
             op = self
-        output = TensorType(dtype = self._output_dtype(input.type.dtype),
-                             broadcastable = [x for i, x in enumerate(input.type.broadcastable) if i not in axis])()
-
+        broadcastable = [x for i, x in enumerate(input.type.broadcastable)
+                         if i not in axis]
+        output = TensorType(dtype=self._output_dtype(input.type.dtype),
+                            broadcastable=broadcastable)()
         return Apply(op, [input], [output])
 
     def __getstate__(self):
@@ -1307,26 +1308,62 @@ class Any(CAReduce):
 
 
 class Sum(CAReduce):
+
     """
     Sums all the values of a tensor along the specified axis(es).
 
-    Equivalent to CAReduce(scalar.add, axis = axis), with the
+    Equivalent to CAReduce(scalar.add, axis=axis), with the
     difference that this defines the gradient of sum wrt its tensor
     input.
     """
-    def __init__(self, axis = None):
+
+    def __init__(self, axis=None, dtype=None):
+        """
+        Constructor.
+
+        :param axis: Axis(es) along which the tensor should be summed
+        (use None to sum over all axes, and a list or tuple to sum along more
+        than one axis).
+
+        :param dtype: The dtype of the internal accumulator and returned
+        tensor. If None, then we use the default dtype which is the same as the
+        input tensor's dtype except when:
+            - the input dtype is a signed integer of precision < 64 bit, in
+              which case we use int64
+            - the input dtype is an unsigned integer of precision < 64 bit, in
+              which case we use uint64
+        This behavior is similar in spirit to that of numpy (except numpy
+        uses the default machine integer while we always use 64 bit integers to
+        avoid platform-dependent behavior).
+
+        IMPORTANT: If you use a custom dtype (!= None), it is strongly advised
+        to set `config.on_opt_error` to 'raise' and to run your code in
+        DebugMode at least once. This is because some optimizations may not
+        currently be able to properly deal with such custom dtypes. Also please
+        note that using a custom dtype may prevent some optimizations from
+        being applied.
+        """
         CAReduce.__init__(self, scalar.add, axis)
+        self.dtype = dtype
+
+    def __eq__(self, other):
+        return CAReduce.__eq__(self, other) and self.dtype == other.dtype
+
+    def __hash__(self):
+        return CAReduce.__hash__(self) ^ hash(self.dtype)
 
     def _output_dtype(self, idtype):
-        # we want to protect against overflow
+        if self.dtype is None:
             return dict(
-                int8='int32',
-                int16='int32',
+                    int8='int64',
+                    int16='int64',
                     int32='int64',
-                uint8='uint32',
-                uint16='uint32',
+                    uint8='uint64',
+                    uint16='uint64',
                     uint32='uint64',
                     ).get(idtype, idtype)
+        else:
+            return self.dtype
 
     def grad(self, inp, grads):
         x, = inp
@@ -1345,7 +1382,8 @@ class Sum(CAReduce):
             else:
                 new_dims.append(i)
                 i += 1
-        return Elemwise(scalar.second)(x, DimShuffle(gz.type.broadcastable, new_dims)(gz)),
+        return Elemwise(scalar.second)(
+                        x, DimShuffle(gz.type.broadcastable, new_dims)(gz)),
 
     def R_op(self, inputs, eval_points):
         # There is just one element in inputs and eval_points, the axis are
@@ -1360,6 +1398,7 @@ class Sum(CAReduce):
         else:
             return "Sum{%s}" % ", ".join(map(str, self.axis))
 
+
 class Prod(CAReduce):
     """
     Multiplies all the values of a tensor along the specified axis(es).

theano/tensor/opt.py

@@ -2301,6 +2301,8 @@ if 0:
     #       that if we can prove the output to this sum has a
     #       zero-size dimension, then it can be replaced by an
     #       appropriately typed and broadcasted zero.
+    # TODO: Remember to take into account the new sum dtype argument if this
+    #       optimization is enabled.
     @register_canonicalize
     @gof.local_optimizer([])
     def local_sum_over_empty(node):
@@ -2852,7 +2854,8 @@ def local_sum_mul_by_scalar(node):
     """
     # TODO: if the the thing inside the Sum is a division,
     # we should get at the numerator....
-    if isinstance(node.op, T.Sum):
+    # TODO Implement for sum.dtype != None.
+    if isinstance(node.op, T.Sum) and node.op.dtype is None:
         thing_summed, = node.inputs
         if thing_summed.owner and thing_summed.owner.op == T.mul:
             terms = thing_summed.owner.inputs
@@ -2906,7 +2909,9 @@ def local_sum_div_dimshuffle(node):
     # dimshuffle is in the numerator, since elemwise inversion of the
     # denominator would still be needed before the summation.
 
-    if isinstance(node.op, T.Sum):
+    # TODO Implement for sum.dtype != None.
+
+    if isinstance(node.op, T.Sum) and node.op.dtype is None:
         axis = node.op.axis
         if axis is None:
             axis = range(node.inputs[0].ndim)
@@ -2995,17 +3000,25 @@ def local_sum_all_to_none(node):
         if node.op.axis is None:
             return
         if set(node.op.axis) == set(range(node.inputs[0].type.ndim)):
-            return [T.Sum(axis=None)(node.inputs[0])]
+            return [T.Sum(axis=None, dtype=node.op.dtype)(node.inputs[0])]
 
 
 @register_canonicalize
 @gof.local_optimizer([])
 def local_sum_sum(node):
-    """Sum(Sum()) -> Sum"""
-    if isinstance(node.op, T.Sum):
+    """
+    Sum(Sum()) -> Sum
+
+    Note that currently we only replace sums with default dtypes, to avoid
+    potential dtype conflict issues.
+    """
+    if isinstance(node.op, T.Sum) and node.op.dtype is None:
         summed, = node.inputs
         if len(summed.clients) == 1:
-            if summed.owner and isinstance(summed.owner.op, T.Sum):
+            if (summed.owner and
+                isinstance(summed.owner.op, T.Sum)
+                and summed.owner.op.dtype is None):
+
                 if summed.owner.op.axis is None:
                     # special case of local_cut_useless_reduce
                     return [T.Sum(None)(summed.owner.inputs[0])]
@@ -3074,7 +3087,8 @@ def local_cut_useless_reduce(node):
 @gof.local_optimizer([])
 def local_sum_alloc(node):
     """ sum(alloc(constant,shapes...)) => constant*prod(shapes)"""
-    if isinstance(node.op, T.Sum):
+    # TODO Implement for sum.dtype != None
+    if isinstance(node.op, T.Sum) and node.op.dtype is None:
         summed, = node.inputs
         if summed.owner and isinstance(summed.owner.op, T.Alloc):
             input = summed.owner.inputs[0]

theano/tensor/tests/test_elemwise.py

 import cPickle, time, unittest
+from itertools import imap
 
 from numpy.testing import dec
 
@@ -498,6 +499,40 @@ class test_IsInf_IsNan(unittest.TestCase):
         return self.run_isfunc('isnan')
 
 
+def test_sum_default_dtype():
+    """
+    Test the default dtype of a sum().
+    """
+    # We try multiple axis combinations even though axis should not matter.
+    axes = [None, 0, 1, [0], [1], [0, 1]]
+    for idx, dtype in enumerate(imap(str, theano.scalar.all_types)):
+        axis = axes[idx % len(axes)]
+        x = tensor.matrix(dtype=dtype).sum(axis=axis)
+        assert x.dtype == dict(
+                int8='int64',
+                int16='int64',
+                int32='int64',
+                uint8='uint64',
+                uint16='uint64',
+                uint32='uint64',
+                ).get(dtype, dtype)
+
+
+def test_sum_custom_dtype():
+    """
+    Test the ability to provide your own output dtype for a sum.
+    """
+    # We try multiple axis combinations even though axis should not matter.
+    axes = [None, 0, 1, [0], [1], [0, 1]]
+    idx = 0
+    for input_dtype in imap(str, theano.scalar.all_types):
+        x = tensor.matrix(dtype=input_dtype)
+        for output_dtype in imap(str, theano.scalar.all_types):
+            axis = axes[idx % len(axes)]
+            assert x.sum(dtype=output_dtype, axis=axis).dtype == output_dtype
+            idx += 1
+
+
 if __name__ == '__main__':
     #unittest.main()
     suite = unittest.TestSuite([test_Prod('test_mul_without_zeros_zeros')])

theano/tensor/tests/test_opt.py

@@ -3134,6 +3134,22 @@ class T_local_sum(unittest.TestCase):
             finally:
                 config.warn.sum_sum_bug = backup
 
+    def test_local_sum_sum_int8(self):
+        """
+        Test that local_sum_sum works when combining two sums on an int8 array.
+
+        This is a regression test for ticket gh-356.
+        """
+        x = tensor.tensor3(dtype='int8')
+        y = x.sum(axis=0).sum(axis=1)
+        backup = config.on_opt_error
+        config.on_opt_error = 'raise'
+        try:
+            # This compilation would fail prior to fix.
+            f = theano.function([x], y)
+        finally:
+            config.on_opt_error = backup
+
 
 class T_local_sum_dimshuffle(unittest.TestCase):
     def setUp(self):