docs: correct poisson_generator rate-between-Runs claim (NEST_REALTIME.md)#17
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…IME.md The doc claimed a poisson_generator's rate could be updated via device.set() between Run()s and that 'this works'. Verified on NEST 3.9 that it does NOT: a poisson_generator bakes its rate into an internal deviate generator at calibration (Prepare), so a post-Prepare set(rate=) is silently ignored and emits zero spikes. dc_generator.amplitude DOES update live; only the Poisson source is affected. Corrected §4 (runtime input injection) and the chunking 'workaround' step 3 to state this and point to the robust fix: a scheduled-time generator (inhomogeneous_poisson_generator for a Poisson spike source / rate_hz; step_rate_generator for rate_inject; step_current_generator for current) whose next value is scheduled at biological_time+dt. This is what the engram reference backend now does for every non-dc drive. Docs only.
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The error
NEST_REALTIME.mdclaimed apoisson_generator's rate could be updated viadevice.set()betweenRun()s and that "this works" (§4 and the chunking 'workaround' step 3).Verified on NEST 3.9 that it does not. A
poisson_generatorbakes its rate into an internal deviate generator at calibration (Prepare()), so a post-Prepareset(rate=)is silently ignored — zero spikes (the rate even reads back correctly).dc_generator.amplitudedoes update live; only the Poisson source is affected.The fix (already what the doc recommended elsewhere)
Corrected §4 and step 3 to state this and point to the robust path the doc already names — a scheduled-time generator whose next value is scheduled at
biological_time + dt:inhomogeneous_poisson_generatorfor a Poisson spike source (rate_hz),step_rate_generatorfor a rate-based input (rate_inject),step_current_generatorfor a scheduled current.This is what the engram reference backend now does for every non-
dcdrive (it keeps the Prepare-once + Run model — noSimulate-per-chunk re-calibration). Docs only; no code/wire change.