def csi_from_sr_and_pod(success_ratio_array, pod_array):
    """Computes CSI (critical success index) from success ratio and POD.
    POD = probability of detection
    :param success_ratio_array: np array (any shape) of success ratios.
    :param pod_array: np array (same shape) of POD values.
    :return: csi_array: np array (same shape) of CSI values.
    """
    return (success_ratio_array ** -1 + pod_array ** -1 - 1.) ** -1