added theano_cuda_ndarray.use() that try to use the gpu for theano shared variable.

__init__.py

@@ -7,14 +7,28 @@ from .var import (CudaNdarrayVariable,
 
 import basic_ops
 import opt
+import cuda_ndarray
 
 import theano.compile.sandbox
 
+import logging, os
+
+def use():
+    handle_shared_float32(True)
+
 def handle_shared_float32(tf):
     """Set the CudaNdarrayType as the default handler for shared float32 arrays
+    
+    Use use(tf) instead as this is a bad name.
     """
     if tf:
+        try:
+            v=os.getenv("THEANO_GPU",0)
+            cuda_ndarray.gpu_init(int(v))
             theano.compile.sandbox.shared_constructor(shared_constructor)
+        except RuntimeError, e:
+            logging.getLogger('theano_cuda_ndarray').warning("WARNING: Won't use the GPU as the initialisation failed."+str(e))
+
     else:
         raise NotImplementedError('removing our handler')