Jakov Mitrovski

Marko Vukolić, Orestis Alpos, Jakov Mitrovski et al.

We introduce Bitcoin-IPC, a software stack and protocol that scales Bitcoin towards helping it become the universal Medium of Exchange (MoE) by enabling the permissionless creation of fully programmable Proof-of-Stake (PoS) Layer-2 chains, called subnets, whose stake is denominated in L1 BTC. Bitcoin-IPC subnets rely on Bitcoin L1 for the communication of critical information, settlement, and security. Our design, inspired by SWIFT messaging and embedded within Bitcoin's SegWit mechanism, enables seamless value transfer across L2 subnets, routed through Bitcoin L1. Uniquely, this mechanism reduces the virtual-byte cost per transaction (vB per tx) by up to 23x, compared to transacting natively on Bitcoin L1, effectively increasing monetary transaction throughput from 7 tps to over 160 tps, without requiring any modifications to Bitcoin L1.

Florian Laurent, Manuel Schneider, Christian Scheller et al.

The Flatland competition aimed at finding novel approaches to solve the vehicle re-scheduling problem (VRSP). The VRSP is concerned with scheduling trips in traffic networks and the re-scheduling of vehicles when disruptions occur, for example the breakdown of a vehicle. While solving the VRSP in various settings has been an active area in operations research (OR) for decades, the ever-growing complexity of modern railway networks makes dynamic real-time scheduling of traffic virtually impossible. Recently, multi-agent reinforcement learning (MARL) has successfully tackled challenging tasks where many agents need to be coordinated, such as multiplayer video games. However, the coordination of hundreds of agents in a real-life setting like a railway network remains challenging and the Flatland environment used for the competition models these real-world properties in a simplified manner. Submissions had to bring as many trains (agents) to their target stations in as little time as possible. While the best submissions were in the OR category, participants found many promising MARL approaches. Using both centralized and decentralized learning based approaches, top submissions used graph representations of the environment to construct tree-based observations. Further, different coordination mechanisms were implemented, such as communication and prioritization between agents. This paper presents the competition setup, four outstanding solutions to the competition, and a cross-comparison between them.