Custom Backends

livn ships with built-in backends, but you can use any Python module that exports an Env class implementing the livn Env protocol.

Usage

Set LIVN_BACKEND to the fully qualified import path of your backend module:

export LIVN_BACKEND=my_package.backend

Then use livn as normal as the custom Env is resolved automatically:

from livn import make

env = make("EI1")  # uses my_package.backend.Env

Writing a custom backend

A backend module must export an Env class that implements the Env protocol. At minimum:

# my_package/backend.py

from livn.types import Env as EnvProtocol
from livn.stimulus import Stimulus

class Env(EnvProtocol):
    def __init__(self, system, model=None, io=None, seed=123, comm=None, subworld_size=None):
        ...

    def init(self):
        # Load cells, connections, etc.
        ...
        return self

    def run(self, duration, stimulus=None, dt=0.025, **kwargs):
        # Run simulation, return (spike_ids, spike_times, voltage_ids, voltages, current_ids, currents)
        ...

    def record_spikes(self, population=None):
        ...
        return self

    def record_voltage(self, population=None, dt=0.1):
        ...
        return self

    # ... other Env protocol methods

TIP

Your backend can reuse livn.types, livn.stimulus, livn.system, etc., only the simulation engine needs to be custom.