As an aside, if `Input_SD.n_events = 0` is the canonical way of clearing a spike recorder, maybe a `clear` function could be added. That's a bit easier to document and find?

On Mon, 29 Nov 2021, 22:24 Jochen Martin Eppler, <> wrote:

Dear Maryada,

I have just played a bit with your example (see attachment for a slightly extended and reformatted version) and as far as I can see, NEST behaves exactly as expected (and documented).

Please let me explain:

  • When using the recording backend ascii with the kernel attribute overwrite_files set to True, you have to move files away at the location in your script saying do something, otherwise the data files get overwritten by each new call to Simulate() and you consequently get to see only the results from the last run (which is what you report).

  • If you set overwrite_files to False, and did not move the file away, you will get an error upon repeated calls to Simulate(), as the file to be created by the backend already exists.

  • When using the recording backend memory, overwrite_files is not even considered, as that does not actually write files.

  • Data just accumulates in the recording backend memory until it is explicitly cleared by running Input_SD.n_events = 0.

See the linked backend documentation pages for more information.

I hope this helps to clear up things.


On 29.11.21 18:32, Maryada Maryada wrote:

Dear NEST users,

I am trying to debug my network and I found that my spike_recorder with ascii option isn't working as expected.
I am simulating a network for a few milliseconds (say 1000. ms) and then do some structure changes and then re-run for another phase of a few ms (say 4000. ms)
In the compact version, I am trying to see how this sample code would work.
import nest
                     "overwrite_files": True,
                      "data_path": './Debug-Log',
                      "data_prefix": 'DEBUG-SPIKE-REC',
noise_device = nest.Create("poisson_generator",params={'start': 0.,'rate' : 100.})
sd_params = {
            "record_to": 'ascii',
            "label": "Input_spike_recorder"
Input_SD = nest.Create("spike_recorder",1, params=sd_params)
# do something here

Issue: I only get the data recorded from 100th millisecond but for memory, I get all the data from 0-200 ms.
This behavior is consistent for both overwrite_files as True and False.
In the previous version (v2.20) I also used the same approach and had no issues. Is there a newer way to do such a simulation paradigm?
I didn't find anything on this on the comparison page of  NESTv2.x and NESTv3.x

Am I missing something? It's really important for my work, I hope I could find a solution.
Thanks and Regards


NEST Users mailing list --
To unsubscribe send an email to

Dr. Jochen Martin Eppler
Phone: +49(2461)61-96653
Simulation Laboratory Neuroscience
Jülich Supercomputing Centre
Institute for Advanced Simulation

Forschungszentrum Juelich GmbH
52425 Juelich
Sitz der Gesellschaft: Juelich
Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
Vorsitzender des Aufsichtsrats: MinDir Volker Rieke
Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender),
Karsten Beneke (stellv. Vorsitzender), Prof. Dr. Astrid Lambrecht,
Prof. Dr. Frauke Melchior

NEST Users mailing list --
To unsubscribe send an email to