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NEST is now part of SPEC CPU 2026
by Hans Ekkehard Plesser 05 May '26

05 May '26

Dear NEST Users and Developers, Today is an exciting day in the history of NEST: The NEST Simulator is now part of the SPEC CPU 2026 industry benchmark. You can find the list of benchmarks here https://www.spec.org/cpu2026/docs/overview.html#Q13, where NEST is included with two cases (single and multithreaded). SPECrate®2026 Floating Point: nest.767_r SPECspeed®2026 Floating Point: nest.867_s For more on SPEC CPU 2026, see Madhav, M., Lee, A., Mejia, A., Moore, B., Soppadandi, C., Cambly, C., Müllner, C., Bowers, D., Reiner, D., Bakhvalov, D., Zhao, D., Voth, D., Xue, F., Silber-Chaussumier, F., Bucek, J., Southern, J., Liu, J., Himer, J., Henning, J., … Todorovski, Z. (2026). SPEC CPU: The Next Generation (Version 1). arXiv. https://doi.org/10.48550/ARXIV.2605.01575 The two-year process of getting NEST ready for SPEC CPU 2026 is documented in the now closed issue https://github.com/nest/nest-simulator/issues/3217. I consider the inclusion of the NEST Simulator in the SPEC CPU 2026 industry benchmark a tremendous validation of over 30 years of focused work on quality research software engineering and would like to thank all who have contributed to NEST code for making this success possible. I'd also like to thank Mahesh Madhav from Ampere Computing for promoting NEST as a SPEC CPU test case and for the excellent collaboration in getting NEST ready for the benchmark. All the best! Hans Ekkehard -- Prof. Dr. Hans Ekkehard Plesser Research Committee Chair, Faculty of Science and Technology Department of Data Science Faculty of Science and Technology Norwegian University of Life Sciences PO Box 5003, 1432 Aas, Norway Phone +47 6723 1560 Email hans.ekkehard.plesser(a)nmbu.no<mailto:hans.ekkehard.plesser@nmbu.no> Home http://arken.nmbu.no/~plesser

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Open NEST Developer Video Conference Monday May 4, at 11:30 CEST (UTC+0200)
by Dennis Terhorst 04 May '26

04 May '26

Dear NEST Users & Developers! I would like to invite you to our next fortnightly Open NEST Developer Video Conference today *Monday May 4, at 11:30 CEST (UTC+0200).* As usual, in the Project team round, a contact person of each team will give a short statement summarizing ongoing and planned work in the team and highlight cross-cutting points that need discussion among the teams. The remainder of the meeting we would go into a more in-depth discussion of topics that came up on the mailing list or that are suggested by the teams. Feel free to join the meeting also if it’s just to bring your own quick questions for direct discussion in the in-depth section. Agenda * Welcome * Review of NEST User Mailing List * Project team round * In-depth discussion The agenda for this meeting is also available online, see https://github.com/nest/nest-simulator/wiki/2026-05-04-Open-NEST-Developer-… <https://github.com/nest/nest-simulator/wiki/2026-05-04-Open-NEST-Developer-…> Looking forward to seeing you soon! Cheers, Dennis Terhorst Log-in information We use a virtual conference room provided by DFN <https://www.dfn.de/en/> (Deutsches Forschungsnetz). You can use the web client to connect. We however encourage everyone to use a headset for better audio quality or even a proper video conferencing system (see below) or software when available. Web client * Visit https://conf.dfn.de/webapp/conference/97938800 <https://conf.dfn.de/webapp/conference/97938800> * Enter your name and allow your browser to use camera and microphone * The conference does not need a PIN to join, just click join and you’re in. In case you see a dfnconf logo and the phrase “Auf den Meetingveranstalter warten”, just be patient, the meeting host needs to join first (a voice will tell you). VC system/software How to log in with a video conferencing system, depends on you VC system or software. * Using the H.323 protocol (eg Polycom): |vc.dfn.net##97938800| or |194.95.240.2##97938800| * Using the SIP protocol:97938800@vc.dfn.de <mailto:97938800@vc.dfn.de> * By telephone: |+49-30-200-97938800| For those who do not have a video conference system or suitable software, Polycom provides a pretty good free app for iOS and Android, so you can join from your tablet (Polycom RealPresence Mobile, available from AppStore/PlayStore). Note that firewalls may interfere with videoconferencing in various and sometimes confusing ways. For more technical information on logging in from various VC systems, please see http://vcc.zih.tu-dresden.de/index.php?linkid=1.1.3.4 <http://vcc.zih.tu-dresden.de/index.php?linkid=1.1.3.4> -- Dipl.-Phys. Dennis Terhorst Coordinator Software Development Institute for Advanced Simulation (IAS-6) Computational and Systems Neuroscience & JARA-Institute Brain Structure-Function Relationships (INM-10) Institute of Neuroscience and Medicine Jülich Research Center, Member of the Helmholz Association 52425 Jülich, Germany http://www.csn.fz-juelich.de/ --------------------------------------------------------------------------------------------- Forschungszentrum Jülich GmbH 52425 Jülich Sitz der Gesellschaft: Jülich Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Stefan Müller Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende), Dr. Stephanie Bauer (stellvertretende Vorsitzende), Prof. Dr. Ir. Pieter Jansens, Prof. Dr. Laurens Kuipers ---------------------------------------------------------------------------------------------

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NEST Conference 2026: Abstract submission deadline on Sunday 3 May
by Hans Ekkehard Plesser 30 Apr '26

30 Apr '26

Dear NEST Users! Just a quick reminder that the deadline for submitting your abstract to the NEST Conference 2026 is this Sunday, 3 May. Please submit your abstract on the conference website https://www.nest-initiative.org/conference. Best, Hans Ekkehard -- Prof. Dr. Hans Ekkehard Plesser Research Committee Chair, Faculty of Science and Technology Department of Data Science Faculty of Science and Technology Norwegian University of Life Sciences PO Box 5003, 1432 Aas, Norway Phone +47 6723 1560 Email hans.ekkehard.plesser(a)nmbu.no<mailto:hans.ekkehard.plesser@nmbu.no> Home http://arken.nmbu.no/~plesser

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Hackathon at the University of Sussex, UK, 22-25 June 2026
by Johanna Senk 27 Apr '26

27 Apr '26

Dear NEST Users, We are organising an *application-oriented hackathon* in the week after the NEST Conference 2026. This in-person event will take place at the *University of Sussex in Brighton, UK, on the 22-25 June*. Your are welcome to bring your ideas for new NEST features and get started implementing them with the help of experienced NEST developers. For more information and *registration*, you may visit: https://events.hifis.net/event/3366 Please note that while participation is free of charge, costs for travelling, accommodation, food/drinks, etc. are *at your own expense.* If you have any questions, please don't hesitate to contact me ( J.Senk(a)sussex.ac.uk ). Best regards, Johanna Senk -- Dr. Johanna Senk Institute for Advanced Simulation (IAS-6) Computational and Systems Neuroscience Jülich Research Centre, Juelich, Germany --------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------- Forschungszentrum Jülich GmbH 52425 Jülich Sitz der Gesellschaft: Jülich Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Stefan Müller Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende), Karsten Beneke (stellv. Vorsitzender), Dr. Ir. Pieter Jansens --------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------- The Forschungszentrum Jülich is currently switching to a new certificate provider for digitally signing emails. During this changeover, the DFN Community PKI certificate used to sign this email may be displayed as invalid.

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NESTML example of neuromodulated STDP synapse
by Han-Jia Jiang 24 Apr '26

24 Apr '26

Dear all, My colleague and I were trying to run a NESTML example, the neuromodulated STDP synapse, as specified here <https://github.com/nest/nestml/blob/main/models/synapses/neuromodulated_std…>. We encountered some problems. First we made some workarounds in order to avoid some errors associated with NESTML. We changed *emit_spike(w)* to *emit_spike()* in the synapse model to avoid the following error: * [15,neuromodulated_stdp_synapse_nestml, ERROR, [33:4;34:4]]: emit_spike() function was called, but with different parameter types than the output port was defined with! Then we added *d ms = 1 ms* and *"delay_variable": {"neuromodulated_stdp_synapse": "d"}* to avoid another set of error: * [29,neuromodulated_stdp_synapse_nestml__with_iaf_psc_delta_neuron_nestml, ERROR]: Delay variable is not specified for synapse model. * [29,neuromodulated_stdp_synapse_nestml__with_iaf_psc_delta_neuron_nestml, ERROR]: Delay variable 'd' not found in synapse. Finally, we failed during the make stage and could not overcome. I attach the code (adapted from the tutorial <https://nestml.readthedocs.io/en/latest/tutorials/stdp_dopa_synapse/stdp_do…>; neuron model as in here <https://github.com/nest/nestml/blob/main/models/neurons/iaf_psc_delta_neuro…>), as well as the error messages (two files because we tried NEST 3.8 and 3.9 respectively) from the make stage. Could you provide any advice on how to solve this? Thank you in advance for your help! Best regards, Han-Jia Jiang

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Open NEST Developer Video Conference Monday April 20, at 11:30 CEST (UTC+0200)
by Dennis Terhorst 20 Apr '26

20 Apr '26

Dear NEST Users & Developers! I would like to invite you to our next fortnightly Open NEST Developer Video Conference today *Monday April 20, at 11:30 CEST (UTC+0200).* As usual, in the Project team round, a contact person of each team will give a short statement summarizing ongoing and planned work in the team and highlight cross-cutting points that need discussion among the teams. The remainder of the meeting we would go into a more in-depth discussion of topics that came up on the mailing list or that are suggested by the teams. Feel free to join the meeting also if it’s just to bring your own quick questions for direct discussion in the in-depth section. Agenda * Welcome * Review of NEST User Mailing List * Project team round * In-depth discussion o NEST 3.10 release status The agenda for this meeting is also available online, see https://github.com/nest/nest-simulator/wiki/2026-04-20-Open-NEST-Developer-… <https://github.com/nest/nest-simulator/wiki/2026-04-20-Open-NEST-Developer-…> Looking forward to seeing you soon! Cheers, Dennis Terhorst Log-in information We use a virtual conference room provided by DFN <https://www.dfn.de/en/> (Deutsches Forschungsnetz). You can use the web client to connect. We however encourage everyone to use a headset for better audio quality or even a proper video conferencing system (see below) or software when available. Web client * Visit https://conf.dfn.de/webapp/conference/97938800 <https://conf.dfn.de/webapp/conference/97938800> * Enter your name and allow your browser to use camera and microphone * The conference does not need a PIN to join, just click join and you’re in. In case you see a dfnconf logo and the phrase “Auf den Meetingveranstalter warten”, just be patient, the meeting host needs to join first (a voice will tell you). VC system/software How to log in with a video conferencing system, depends on you VC system or software. * Using the H.323 protocol (eg Polycom): |vc.dfn.net##97938800| or |194.95.240.2##97938800| * Using the SIP protocol:97938800@vc.dfn.de <mailto:97938800@vc.dfn.de> * By telephone: |+49-30-200-97938800| For those who do not have a video conference system or suitable software, Polycom provides a pretty good free app for iOS and Android, so you can join from your tablet (Polycom RealPresence Mobile, available from AppStore/PlayStore). Note that firewalls may interfere with videoconferencing in various and sometimes confusing ways. For more technical information on logging in from various VC systems, please see http://vcc.zih.tu-dresden.de/index.php?linkid=1.1.3.4 <http://vcc.zih.tu-dresden.de/index.php?linkid=1.1.3.4> -- Dipl.-Phys. Dennis Terhorst Coordinator Software Development Institute for Advanced Simulation (IAS-6) Computational and Systems Neuroscience & JARA-Institute Brain Structure-Function Relationships (INM-10) Institute of Neuroscience and Medicine Jülich Research Center, Member of the Helmholz Association 52425 Jülich, Germany http://www.csn.fz-juelich.de/ --------------------------------------------------------------------------------------------- Forschungszentrum Jülich GmbH 52425 Jülich Sitz der Gesellschaft: Jülich Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Stefan Müller Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende), Dr. Stephanie Bauer (stellvertretende Vorsitzende), Prof. Dr. Ir. Pieter Jansens, Prof. Dr. Laurens Kuipers ---------------------------------------------------------------------------------------------

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NEST Conference 2026 — Abstract Submission Deadline extended to 3 May
by Hans Ekkehard Plesser 10 Apr '26

10 Apr '26

Dear all, The abstract submission deadline for the NEST Conference 2026 has been extended to Sunday, 3 May. We are inviting contributions to the conference, including talks, "posters" and workshops on specific topics. Do not miss out on contributing to this exciting event! The NEST Conference provides an opportunity for the NEST Community to meet, exchange success stories, swap advice, learn about current developments in and around NEST spiking network simulation and its application. Take the opportunity to advance your skills in using NEST at our hands-on workshops! This year's conference will again take place as a virtual conference on Tuesday/Wednesday 16/17 June 2026. We are delighted to welcome * Marja-Leena Linne, Tampere University * Maxime Carriere and Fynn Dobler, Freie Universität Berlin * Agnes Korcsak-Gorzo, Forschungszentrum Jülich * Pablo Martínez Cañada, University of Granada as keynote speakers at the conference. For more information on how to submit your contribution, register and participate, please visit the conference website: https://nest-simulator.org/conference We are looking forward to seeing you all in June! Hans Ekkehard Plesser and the conference organizing committee -- Prof. Dr. Hans Ekkehard Plesser Research Committee Chair, Faculty of Science and Technology Department of Data Science Faculty of Science and Technology Norwegian University of Life Sciences PO Box 5003, 1432 Aas, Norway Phone +47 6723 1560 Email hans.ekkehard.plesser(a)nmbu.no<mailto:hans.ekkehard.plesser@nmbu.no> Home http://arken.nmbu.no/~plesser

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Test
by Jochen Martin Eppler 31 Mar '26

31 Mar '26

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Changes in main branch: Now using std::variant<> instead of boost::any in Dictionary
by Hans Ekkehard Plesser 27 Mar '26

27 Mar '26

Dear NEST Users and Developers! Last night, we made another "under the hood" change to NEST, replacing boost::any with std::variant<> as the flexible data type for entries in the dictionaries that we use to move data between Python and the NEST Kernel (thanks to Jan for the implementation and Agnes and Catherine for reviewing!). If you are a user, this should not affect you at all. If you are writing your own model code in C++, you may need to make small adjustments in case you pass unsigned integers. You can find the details here: https://nest-simulator.readthedocs.io/en/main/whats_new/v3.10/index.html#wh… If you are a core developer, you may want to take a look at the doxygen documentation in libnestutil/dictionary.h for implementation details. Note that we recently changed the default on our ReadTheDocs page: You will land at "stable", which now is always the latest release, currently NEST 3.9. To see the documentation for the most recent code in the main branch, you need to explicitly select "main". Best, Hans Ekkehard -- Prof. Dr. Hans Ekkehard Plesser Research Committee Chair, Faculty of Science and Technology Department of Data Science Faculty of Science and Technology Norwegian University of Life Sciences PO Box 5003, 1432 Aas, Norway Phone +47 6723 1560 Email hans.ekkehard.plesser(a)nmbu.no<mailto:hans.ekkehard.plesser@nmbu.no> Home http://arken.nmbu.no/~plesser

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Re: Heaviside function in a Kernel?
by Charl Linssen 18 Mar '26

18 Mar '26

Dear Jeanne, I have taken a look at the code that Zhang et al. made available on GitHub, but I'm afraid that to really grok it I have to do a deep dive. I am not sure why the authors would take the max-value of the postsynaptic response rather than accumulating them; could it be related to a conductance based mechanism like shunting inhibition? Your grid search fit in any case looks like a promising approximation. In conversation with Prof. Markus Diesmann, he pointed me to another way in which the polynomial system could be integrated. Please see the example in this paper (Rotter et al. 1999) <https://brainworks.biologie.uni-freiburg.de/1999/journal%20papers/RotterDie…> on the bottom left of page 385. Using this method, you should be able to integrate a numerically exact (up to floating point precision) solution of the original polynomial. I made a little test script that performs this simulation and also clips the polynomial to zero (see the bottom panel in the plot below). Hopefully this will be useful to you as a basis for further work. Please don't hesitate to get/stay in touch about further steps in the implementation. With kind regards, Charl On Thu, Mar 5, 2026, at 07:04, Jeanne Barthelemy wrote: > > Dear Charl, > > Thank you very much for your follow up. > I agree that using a linear system of ODEs would be preferable. I made a proxy version that uses a beta kernel (inspired from iaf_cond_beta_neuron.nestml). The rise and decay time constants, and a modulatory parameter to scale the conductance, may be tuned to approximate the polynomials derived by Zhang and colleagues. In the attachment, my result is provided from a simple grid search, comparing the proxy with two exponentials and the polynomial from Zhang and colleagues. > > It may be interesting indeed to perform a ReScience paper comparing the beta kernel version in NESTML with the version from Zhang and colleagues (for your information, their matlab code is available on github). However, in order to do so, another part of their implementation puzzles me. Their total model takes into account the polynomial component, but also multiplied by an inhibition efficiency that relies on the firing rate of the ChI population. In their code, from my understanding, they compute the inhibition at time i + k via a multiplication (efficiency due to ChI firing at time i X inhibition along time via the value of the polynomial at time k), but keep only the maximum value along i and k, rather than actually summing the effect of spikes at distinct times. I am not sure to understand the reason between this modelling choice. Do you think it may be interesting as well to compare this with a more traditional approach in NESTML, where the efficiency is computed online at the time t of the simulation, and the beta kernel allows to integrate all past spikes? Even if we integrate a new modulatory parameter for scaling the entire inhibition response and fit better the average behavior of the model from Zhang and colleagues． > > Please do not hesitate to let me know your thoughts about this. > Thank you, > Kind regards, > Jeanne Barthelemy > > > *From:* Charl Linssen <nest-users(a)turingbirds.com> > *Sent:* Thursday, March 5, 2026 1:47 AM > *To:* users(a)nest-simulator.org <users(a)nest-simulator.org> > *Subject:* [NEST Users] Re: Heaviside function in a Kernel? > > Dear Jeanne, > > Much obliged for the link to the paper and clarification. If a postsynaptic response is well described by a polynomial, it makes total sense to use that as part of model fitting. From a simulation perspective, it may be more efficient though to describe the response in the form of a (preferably linear) system of ODEs. Therefore if you could use the alpha or beta functions for the postsynaptic response, that would indeed be an ideal solution. > > That being said, please let me know if this could create an interesting opportunity for a ReScience paper comparing the responses of the alpha versus the polynomial; we could then look into doing a precise simulation of the polynomial more deeply. > > My colleagues also kindly attended me to the possibility of using the so-called Linear Chain Trick in the context of delay differential equations, which could be an attractive alternative method for fitting and simulating postsynaptic responses. > > Cheers, with kind regards, > Charl > > > On Tue, Mar 3, 2026, at 06:04, Jeanne Barthelemy wrote: >> Dear Charl, >> >> Thank you very much for this relevant answer. >> I was trying to reproduce with NESTML the model from this paper: Zhang, Yan-Feng, et al. "An axonal brake on striatal dopamine output by cholinergic interneurons." *Nature Neuroscience* 28.4 (2025): 783-794.". Though, I am starting to think that approximating their model with an alpha kernel, without any need for an heaviside function, may be a better option in my case. >> >> Thank you very much, >> Kind regards, >> Jeanne Barthelemy >> >> >> *From:* Charl Linssen <nest-users(a)turingbirds.com> >> *Sent:* Monday, March 2, 2026 11:47 PM >> *To:* users(a)nest-simulator.org <users(a)nest-simulator.org> >> *Subject:* [NEST Users] Re: Heaviside function in a Kernel? >> >> Dear Jeanne, >> >> Thank you for writing in and thank you for this interesting question. I'm sorry that the advanced kernel shape you need is not supported by the numerical backend. The central issue with this kernel is that it cannot be described by a linear and time-invariant system. As such it makes adding contributions from different spikes much harder, because you cannot simply add the effects of different spikes together (something that only makes sense mathematically for LTI systems). >> >> Actually, there are two components that make this a tricky kernel to work with: the factor *t*^2 as well as the Heaviside function. May I ask how you obtained the shape and parameters of this kernel? Would it be possible to replace it with an LTI kernel like the “alpha” or “beta” function? (You can have a look at the neuron models in NESTML for a definition of both.) >> >> As for the Heaviside function: I tried to think of an approach to implement this behaviour. One thing you could do is to create an additional buffer in the model that corresponds to the 200 ms time interval. When a spike comes in (let's say at time *t*_sp), it would then not only trigger the kernel response (ignoring the Heaviside term), but also add an entry to the buffer, so that 200 ms later, a *negative *contribution would be added to the state, cancelling out the value at that time to reset the value back to zero. The magnitude of this negative contribution would be of equal magnitude to the kernel at time *t_*sp + 200 ms, but with an opposite sign, so that it cancels out. I believe this would work well, even with multiple spikes arriving all the time. >> >> If you can confirm that you are interested in making an implementation of this, I would be happy to look at it together. >> >> Much obliged, >> Charl >> >> >> On Fri, Feb 27, 2026, at 10:20, Jeanne Barthelemy wrote: >>> Dear all, >>> >>> This is a question about best practices for NESTML. I would like to build in the equations block a Kernel, such as for instance: >>> >>> "kernel inh_time_end = ((-0.00002*t*t)/(pow(tau,2.0)) + 0.0087*t/tau + 0.006)/tau" >>> >>> , but modulated by the heaviside function H depending on 200 - t (i.e., H(200.0 ms -t)). To sum up, I would like to get the following kernel: >>> >>> "kernel inh_time_end_modulated = H(200.0 ms -t)*((-0.00002*t*t)/(pow(tau,2.0)) + 0.0087*t/tau + 0.006)/tau" >>> >>> There does not appear to be a direct implementation of the heaviside function H in nestml. I tried to build my own function to convert booleans to 1.0 or 0.0 in my NestML model, upon the condition "200.0 ms > t", and use that instead of the heaviside, but the model is really slow to build on my laptop. I tried other versions with if conditions in the update block, or ternary operators, but they all led to bugs. So, I am unsure of the correct practice to implement an heaviside-modulated polynomial kernel. If anyone has a good and fast solution to propose I would be very happy to learn about it ! >>> >>> Thank you very much, >>> Kind regards, >>> Jeanne BARTHELEMY >>> _______________________________________________ >>> NEST Users mailing list -- users(a)nest-simulator.org >>> To unsubscribe send an email to users-leave(a)nest-simulator.org >>> >> >> >> *CAUTION:* This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. >> >> >> _______________________________________________ >> NEST Users mailing list -- users(a)nest-simulator.org >> To unsubscribe send an email to users-leave(a)nest-simulator.org >> > > > *CAUTION:* This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. > > > _______________________________________________ > NEST Users mailing list -- users(a)nest-simulator.org > To unsubscribe send an email to users-leave(a)nest-simulator.org > > > *Attachments:* > • inhibition_score.pdf

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