Merge pull request #2110 from nouiz/bug_reduction_join

theano/configdefaults.py

@@ -422,6 +422,19 @@ AddConfigVar('warn.signal_conv2d_interface',
              BoolParam(warn_default('0.7')),
              in_c_key=False)
 
+AddConfigVar('warn.reduce_join',
+             ('Your current code is fine, but Theano versions '
+              'prior to 0.7 (or this development version) '
+              'might have given an incorrect result. '
+              'To disable this warning, set the Theano flag '
+              'warn.reduce_join to False. The problem was an '
+              'optimization that modify the pattern '
+              '"Reduce{scalar.op}(Join(axis=0, a, b), axis=0)", '
+              'did not checked the reduction axis. So if the '
+              'reduction axis is not 0, you got wrong answer.'),
+             BoolParam(warn_default('0.7')),
+             in_c_key=False)
+
 AddConfigVar('compute_test_value',
         ("If 'True', Theano will run each op at graph build time, using "
          "Constants, SharedVariables and the tag 'test_value' as inputs "

theano/tensor/opt.py

@@ -3483,10 +3483,14 @@ ALL_REDUCE = [T.elemwise.CAReduce, T.elemwise.All, T.elemwise.Any,
 @register_uncanonicalize  # Needed for MaxAndArgmax -> CAReduce
 @gof.local_optimizer(ALL_REDUCE)
 def local_reduce_join(node):
-    """Reduce{scalar.op}(Join(a, b), axis=0) -> Elemwise{scalar.op}(a, b)
+    """Reduce{scalar.op}(Join(axis=0, a, b), axis=0) -> Elemwise{scalar.op}(a, b)
 
     :note: supported scalar.op are Maximum, Mimimum in some cases and
-    Add and Mul in all cases.
+        Add and Mul in all cases.
+
+    :note: Currently we must reduce on axis 0. It is probably
+        extensible to the case where we join and reduce on the same
+        set of axis.
 
     """
     if (isinstance(node.op, T.CAReduce) and
@@ -3498,7 +3502,7 @@ def local_reduce_join(node):
             return
 
         if isinstance(node.op.scalar_op, (scalar.Maximum, scalar.Minimum)):
-            #Support only 2 inputs for now
+            # Support only 2 inputs for now
             if len(join.inputs) != 3:
                 return
         elif not isinstance(node.op.scalar_op, (scalar.Add, scalar.Mul)):
@@ -3517,9 +3521,36 @@ def local_reduce_join(node):
                 return
             new_inp.append(inp.inputs[0])
         ret = Elemwise(node.op.scalar_op)(*new_inp)
-        if ret.dtype == node.outputs[0].dtype:
-            return [ret]
-        #else the reduction do something about the dtype.
+
+        if ret.dtype != node.outputs[0].dtype:
+            # The reduction do something about the dtype.
+            return
+
+        # I put this warning late to don't add extra warning.
+        if len(node.op.axis) != 1 or 0 not in node.op.axis:
+            if theano.config.warn.reduce_join:
+                _logger.warn((
+                    'Your current code is fine, but Theano versions '
+                    'prior to 0.7 (or this development version Sept 2014) '
+                    'might have given an incorrect result for this code. '
+                    'To disable this warning, set the Theano flag '
+                    'warn.reduce_join to False. The problem was an '
+                    'optimization that modify the pattern '
+                    '"Reduce{scalar.op}(Join(axis=0, a, b), axis=0)", '
+                    'did not checked the reduction axis. So if the '
+                    'reduction axis is not 0, you got wrong answer.'
+                    ))
+            return
+
+        # We add the new check late to don't add extra warning.
+        try:
+            join_axis = get_scalar_constant_value(join.inputs[0])
+            if join_axis != node.op.axis[0]:
+                return
+        except NotScalarConstantError:
+            return
+
+        return [ret]
 
 
 @register_canonicalize('fast_compile')

theano/tensor/raw_random.py

@@ -75,6 +75,11 @@ class RandomStateType(gof.Type):
             else:
                 raise NotImplementedError()
         return size
+
+    @staticmethod
+    def may_share_memory(a, b):
+        return a is b
+
 # Register RandomStateType's C code for ViewOp.
 theano.compile.register_view_op_c_code(
         RandomStateType,

theano/tensor/tests/test_opt.py

@@ -3858,7 +3858,7 @@ class T_local_reduce(unittest.TestCase):
         x = numpy.asarray([[1, 0], [3, 4]], dtype=config.floatX)
         y = numpy.asarray([[4, 0], [2, 1]], dtype=config.floatX)
         z = numpy.asarray([[5, 0], [1, 2]], dtype=config.floatX)
-
+        # Test different reduction scalar operation
         for out, res in [
             (T.max((vx, vy), 0), numpy.max((x, y), 0)),
             (T.min((vx, vy), 0), numpy.min((x, y), 0)),
@@ -3873,6 +3873,41 @@ class T_local_reduce(unittest.TestCase):
             assert len(topo) <= 2, out
             assert isinstance(topo[-1].op, T.Elemwise), out
 
+        # Test different axis for the join and the reduction
+        A = theano.shared(numpy.array([1, 2, 3, 4, 5]))
+
+        f = theano.function([], T.sum(T.stack(A, A), axis=0), mode=self.mode)
+        assert numpy.allclose(f(), [2, 4, 6, 8, 10])
+        topo = f.maker.fgraph.toposort()
+        assert isinstance(topo[-1].op, T.Elemwise)
+
+        # Test a case that was bugged in a old Theano bug
+        try:
+            old = theano.config.warn.reduce_join
+            theano.config.warn.reduce_join = False
+            f = theano.function([], T.sum(T.stack(A, A), axis=1),
+                                mode=self.mode)
+        finally:
+            theano.config.warn.reduce_join = old
+        assert numpy.allclose(f(), [15, 15])
+        topo = f.maker.fgraph.toposort()
+        assert not isinstance(topo[-1].op, T.Elemwise)
+
+        # This case could be optimized
+        A = theano.shared(numpy.array([1, 2, 3, 4, 5]).reshape(5, 1))
+        f = theano.function([], T.sum(T.concatenate((A, A), axis=1), axis=1),
+                            mode=self.mode)
+        assert numpy.allclose(f(), [2, 4, 6, 8, 10])
+        topo = f.maker.fgraph.toposort()
+        assert not isinstance(topo[-1].op, T.Elemwise)
+
+        A = theano.shared(numpy.array([1, 2, 3, 4, 5]).reshape(5, 1))
+        f = theano.function([], T.sum(T.concatenate((A, A), axis=1), axis=0),
+                            mode=self.mode)
+        assert numpy.allclose(f(), [15, 15])
+        topo = f.maker.fgraph.toposort()
+        assert not isinstance(topo[-1].op, T.Elemwise)
+
 
 class T_local_sum_dimshuffle(unittest.TestCase):
     def setUp(self):