minor: change device selection in mdd_cupy.py

Co-authored-by: Rohan Babbar  <[email protected]>

Author: mrava87

tutorials_cupy/mdd_cupy.py

@@ -23,7 +23,8 @@
 size = MPI.COMM_WORLD.Get_size()
 dtype = np.float32
 cdtype = np.complex64
-cp.cuda.Device(device=rank).use();
+device_count = cp.cuda.runtime.getDeviceCount()
+cp.cuda.Device(rank % device_count).use()
 
 ###############################################################################
 # Let's start by creating a set of hyperbolic events to be used as