[NEST Users] Error in Simulate

We have encountered the following error: Traceback (most recent call last): File "all_v2.py", line 364, in <module> nest.Simulate(sim_time) File"/opt/soft/nest-2.18.0/lib64/python3.6/site-packages/nest/ll_api.py",line 246, in stack_checker_func return f(*args, **kwargs) File"/opt/soft/nest-2.18.0/lib64/python3.6/site-packages/nest/lib/hl_api_simulation.py",line 66, in Simulate sr('ms Simulate') File"/opt/soft/nest-2.18.0/lib64/python3.6/site-packages/nest/ll_api.py",line 132, in catching_sli_run raise exceptionCls(commandname, message) nest.ll_api.C++Exception: ('C++Exception in Simulate_d:std::bad_alloc', 'C++Exception', <SLILiteral: Simulate_d>, ':std::bad_alloc') Could you help to resolve it? Best regards,Petia Koprinkova-Hristova