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# Authors: R. Ford, A. R. Porter and S. Siso, STFC Daresbury Laboratory

'''File containing a PSyclone transformation script for the Dynamo0p3
API to make asynchronous halo exchanges and overlap their
communication with computation. This can be applied via the -s option
in the generator.py script.

'''


def trans(psy):
    '''A sample transformation script to demonstrate the use of asynchronous
    halo exchanges with overlapping compute and communication for the
    most costly halo exchanges in the (current version of the) LFRic model.

    '''
    from psyclone.transformations import \
        Dynamo0p3RedundantComputationTrans, \
        Dynamo0p3AsyncHaloExchangeTrans, \
        MoveTrans

    schedule = psy.invokes.invoke_list[0].schedule
    print(schedule.view())

    # This transformation removes the halo exchange associated with
    # the grad_p field. This transformation is unnecessary if
    # annexed_dofs is set to True in the config file (although the
    # transformation still works).
    rc_trans = Dynamo0p3RedundantComputationTrans()
    rc_trans.apply(schedule.children[0], {"depth": 1})
    print(schedule.view())

    # This transformation splits the three synchronous halo exchanges
    # (for fields p, hb_inv and u_normalisation) into asynchronous
    # (halo_exchange_start and halo_exchange_end) ones.
    ahex_trans = Dynamo0p3AsyncHaloExchangeTrans()
    for kern in schedule.children[3:0:-1]:
        ahex_trans.apply(kern)
    print(schedule.view())

    # This transformation moves the start of the three halo exchanges
    # before the setval_c loop offering the potential for overlap
    # between communication and computation.
    mtrans = MoveTrans()
    for kern in schedule.children[5:0:-2]:
        mtrans.apply(kern, schedule.children[0])
    print(schedule.view())

    return psy
