Young-Joon Park

Hyungseok Song, Junseok Park, Won-Seok Choi et al.

PCB routing is the task of connecting the nets of a board with copper traces under strict design rules, yet learning-based methods still lag behind rule-based routers. We introduce PCBWorld, an open-source engine-grounded PCB routing environment built on the KiCad EDA engine. As a human engineer does, agents in PCBWorld interactively route a board through the engine's native operations, using its Design Rule Check (DRC) feedback to keep the routing within the design rules. The environment supports both RL policies and tool-using LLM agents. Alongside the environment, PCBWorld-Bench provides three dataset families in KiCad's native board format (.kicad_pcb), covering two types of controllable synthetic instances and 679 real open-source boards. It scores any completed board with eight engine-checked evaluation metrics, regardless of the routing method. In our experiments, agents in PCBWorld consistently outperformed grid-action RL policies and open-loop LLM baselines, and an RL policy trained only on synthetic boards transferred zero-shot to real boards, approaching rule-based routers. These results position the engine-grounded, interactive approach of PCBWorld as a promising foundation for advancing the routing ability of both RL and LLM agents.

Youngjoon Park

Random forests aggregate tree votes by simple majority, treating all trees as equally informative. We observe that the topological pattern along each tree's root-to-leaf decision path -- where and how often the dominant class label flips along it -- carries a signal of tree reliability that is exploitable for per-sample reweighting. The naive use of this signal is structurally confounded with the predicted class, so we propose a class-conditional ratio weighting that guarantees zero expected class bias by construction. On 30 binary classification benchmarks under a shared-forest, shared-split protocol with 30 repeats, the proposed method is the only one among four compared schemes -- RF, weighted RF, KNORA-Eliminate, KNORA-Union -- to yield a statistically significant accuracy improvement over RF (Wilcoxon p = 0.018), while the three alternatives all fail to do so (p > 0.5). It is also the only scheme without majority-recall regressions, with minority-recall regressions limited to 3/30 datasets -- a one-sided loss to which classical dynamic ensemble selection methods are susceptible. The gain is robust across forest sizes from 100 to 1000 trees.