** 2023 08 09 **
After much more delay than anticipated, we are very happy to present a new Arbor release. Nearly 8 months of work is in it, much of which focussed on speed, optimisation, fixes and build system changes. This release includes Python 3.12 wheels as probably one of the first packages on PyPI 😄.
Major new features
* External Connectivity: Arbor can now interface with other simulators or processes through MPI. Contexts now accept a second MPI communicator and Recipes can implement a ``external_connections_on`` method to specify how simulations might be interacting. [See documentation for more.](https://docs.arbor-sim.org/en/latest/concepts/interconnectivity.html#cross-simulator-interaction)
* Arbor now supports checkpointing and resume from a previously stored checkpoint. Useful when a certain point in time needs to be explored in multiple directions, when you want to rewind to a previous state, etc. [See documentation for more.](https://docs.arbor-sim.org/en/latest/fileformat/serdes.html)
* More painted parameters are now scalable through `iexpr`: temperature, capacitance, resistivity, membrane potential and the following ionic parameters: internal and external concentration, diffusivity, and reversal potential. [See documentation.](https://docs.arbor-sim.org/en/latest/concepts/decor.html#scaling-mechanism-and-membrane-parameters)
* A set of ANN activation functions for NMODL have been added: `sigmoid(x)`, `relu(x)` and `tanh(x)`. Control volume `area` is exposed through NMODL.
* A revamped backend for ARM CPU's that support Scalable Vector Extension (SVE). Arbor and modcc are now fully compatible, so users who have access to A64FX-based HPC can take full advantage of that hardware.