Add theano.sandbox.cuda.unuse()

theano/gof/optdb.py

@@ -66,6 +66,16 @@ multiple time in a DB. Tryed to register "%s" again under the new name "%s".
                                  obj, tag)
             self.__db__[tag].add(obj)
 
+    def remove_tags(self, name, *tags):
+        obj = self.__db__[name]
+        assert len(obj) == 1
+        obj = obj.copy().pop()
+        for tag in tags:
+            if tag in self._names:
+                raise ValueError('The tag of the object collides with a name.',
+                                 obj, tag)
+            self.__db__[tag].remove(obj)
+
     def __query__(self, q):
         if not isinstance(q, Query):
             raise TypeError('Expected a Query.', q)

theano/sandbox/cuda/__init__.py

@@ -437,6 +437,29 @@ def use(device,
 use.device_number = None
 
 
+def unuse():
+    """
+    This undo what was done by the call to
+
+    use('gpu[0-9]', default_to_move_computation_to_gpu=True,
+        move_shared_float32_to_gpu=True,
+        enable_cuda=True)
+
+    This is used in Pylearn2 tests to enable/disable the GPU when needed.
+
+    After this call, the rest of Theano think the GPU shouldn't be used by default.
+    """
+    global cuda_enabled
+    cuda_enabled = False
+    handle_shared_float32(False)
+    optdb.remove_tags('gpu_opt',
+                   'fast_run',
+                   'inplace')
+    optdb.remove_tags('gpu_after_fusion',
+                   'fast_run',
+                   'inplace')
+
+
 def handle_shared_float32(tf):
     """Set the default shared type for float32 tensor to CudaNdarrayType