Weekly Update 2025-03-10 (#258)

* site: weekly update

Author: will-break-it

site/news/2025-03-10-weekly-progress-summary.md

@@ -0,0 +1,49 @@
+---
+title: Weekly Summary – March 10, 2025
+authors:
+- will
+tags: [progress, update, weekly]
+---
+
+This week saw significant progress in simulation capabilities with the successful comparison of Rust and Haskell simulations across **[90 scenarios](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/sims/2025w11/analysis.ipynb)**. We conducted our **first mainnet-scale [analysis](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/sims/2025w11xl/analysis.ipynb) of Leios** on a [mainnet-scale network](https://github.com/input-output-hk/ouroboros-leios/blob/leios-2025w11/sim-rs/test_data/realistic.yaml) of 3000 nodes, revealing unexpected performance benefits from network topology. **[Sharding performance analysis](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/shard-performance.ipynb)** provided important insights into optimization strategies. Both simulation implementations received improvements to enhance realism and comparability, while our formal methods team developed initial trace verification tools for Short Leios.
+
+## Simulation comparison
+
+- Compared [90 scenarios](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/sims/2025w11/analysis.ipynb) between Rust and Haskell simulations at tag [`leios-2025w11`](https://github.com/input-output-hk/ouroboros-leios/releases/tag/leios-2025w11)
+- Recent fixes and adjustments enabled meaningful comparison between simulations
+- Identified [issues](https://github.com/input-output-hk/ouroboros-leios/issues?q=is%3Aissue%20state%3Aopen%20label%3Aquestion) requiring further investigation.
+
+### Analysis of mainnet-scale simulation
+
+- Completed first [analysis](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/sims/2025w11xl/analysis.ipynb) of Leios on a mainnet-scale network simulation using Rust simulator
+- Discovered 3000-node mainnet-scale network transports IBs faster than artificial 100-node network
+- Identified "shortcut" edges in larger networks as likely reason for improved transport speed.
+
+![In-flight time for Input Blocks (IBs)](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/sims/2025w11xl/plots/elapsed-IB-rust.png?raw=true)
+
+### Performance analysis of sharding
+
+- Created [computational models](https://github.com/input-output-hk/ouroboros-leios/blob/weekly-update-2025-03-10/analysis/shard-performance.ipynb) showing relationship between fraction of shards without an IB and expected number of extra IBs
+- Evaluated performance characteristics of the simplest sharding scheme.
+
+![Performance analysis of simple sharding](https://github.com/input-output-hk/ouroboros-leios/raw/weekly-update-2025-03-10/analysis/shard-performance.svg)
+
+## Haskell simulation
+
+- Fixed bug in Relay protocol preventing full diffusion of votes
+- Changed priority of certified EB to be included in RB
+- Added support for output log format sharing a common subset with the Rust sim
+- Analyzed TCP realism in comparison to idealized diffusion
+  - Found higher IB rate and size leads to better diffusion times
+  - Identified ledger state access as significant source of latency.
+
+## Rust simulation
+
+- Added more information to logs (total size of IB, parent id of RB)
+- Implemented same EB selection strategy as Haskell
+- Added validation of IB headers before propagation to neighbors
+- Investigating why the simulation doesn't encounter as much congestion as Haskell.
+
+## Formal methods
+
+- Developed initial trace verifier for Short Leios simulation traces in `leios-trace-verifier`.