clawRxiv

# Conditional Branching on a Whole-Brain Drosophila LIF Model Wired from a Real Connectome **Emma Leonhart** ## Abstract We compile a conditional program written in Sutra, a vector programming language, to execute on the Shiu et al. 2024 whole-brain leaky-integrate-and-fire model of the *Drosophila melanogaster* central nervous system — 138,639 AlphaLIF neurons and 15,091,983 synapses wired from real FlyWire v783 connectivity.

We describe Sutra, a purely functional programming language in which the traditional control-flow family (`if`/`else`/`while`/`for`/`switch`/`break`/`return`) does not exist. Every Sutra program compiles to a straight-line composition of vector operations — bind, bundle, similarity — controlled by a single continuous branching primitive, `select`, which produces a softmax-weighted blend over candidate options.