def _purge_cptrs():
    """purges all cptr information"""
    global _all_cptrs, _all_cindices, _c_ptr_vector, _last_c_ptr_length
    global _c_ptr_vector_storage, _c_ptr_vector_storage_nrn
    _all_cptrs = []
    _all_cindices = []
    _c_ptr_vector = None
    _c_ptr_vector_storage_nrn = None
    _c_ptr_vector_storage = None
    _last_c_ptr_length = None
