Query CUDA for the number of GPUs present.

    Raises
    ------
    Will raise an exception on any CUDA error.

    Returns
    -------
    count : int
        The number of GPUs.

def num_gpus():
    """Query CUDA for the number of GPUs present.

    Raises
    ------
    Will raise an exception on any CUDA error.

    Returns
    -------
    count : int
        The number of GPUs.

    """
    count = ctypes.c_int()
    check_call(_LIB.MXGetGPUCount(ctypes.byref(count)))
    return count.value