Thank you for your reply Hans! 

I am using Nest-2.20.0 installed with Conda on Mac os 10.14 Mojave. I have just tried removing the environment and reinstalling using Conda again, but ran into the same issue. What should I do to troubleshoot this? 

Thank you so much and best wishes,

On Thu, Mar 26, 2020 at 2:52 AM Hans Ekkehard Plesser <> wrote:

Hi Josh,

Thanks for your report! This does not look like a memory issue but may point to some internal inconsistency in NEST.

A few questions:
- Which version of NEST are you using?
- How did you install NEST (looks like you used conda)?
- Which operating system are you using?

Hans Ekkehard

On 25 Mar 2020, at 18:29, wrote:

Hello all,

Hope everyone is staying safe and well in these difficult times.

I am an undergrad who is just getting started with this library, so I want to apologize in advance for the basic question. I am having issues I believe are memory-related when I call GetConnections on rather small networks. Here is my script:

import nest
# memory testing
n = 5 # number of neurons
epop1 = nest.Create("iaf_psc_alpha",n)
epop2 = nest.Create("iaf_psc_alpha",n)
nest.Connect(epop1,epop2,{'rule': 'all_to_all'})

# we can now query the synapses using GetConnections
conns = nest.GetConnections(epop1,target = epop2)

This runs fine for n < 5, but I get the following error with n >=5:

Assertion failed: (source_lid < MAX_LID), function set_source_lid, file /usr/local/miniconda/conda-bld/nest-simulator_1583214474797/work/nestkernel/target_data.h, line 264.
Abort trap: 6

I have run some of the example scripts like brunel_alpha_numpy with a few thousand neurons and they work just fine.

Am I making an improper call to GetConnections here? And if so, what is a better way to dynamically check connectivity?
Alternatively, might there be something wrong with my Nest environment? And if so, what should I look at to troubleshoot this?

Thank you so much for your help.

Best wishes,
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Prof. Dr. Hans Ekkehard Plesser
Head, Data Science Section

Faculty of Science and Technology
Norwegian University of Life Sciences
PO Box 5003, 1432 Aas, Norway

Phone +47 6723 1560

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