Compiling Distributed System Models with PGo [evaluation]
Bibliographic record
Abstract
Distributed systems are difficult to design and implement correctly. In response, both research and industry are exploring applications of formal methods to distributed systems. A key challenge in this domain is the missing link between the formal design of a system and its implementation. Today, practitioners bridge this link through manual effort. We present a language called Modular PlusCal that extends PlusCal by cleanly separating the model of a system from a model of its environment. We then present a compiler tool-chain called PGo that automatically translates MPCal models to TLA+ for model checking, and that also compiles MPCal models to runnable Go code. PGo provides system designers with a new ability to model and check their designs, and then re-use their modeling efforts to mechanically extract runnable implementations of their designs. Our evaluation shows that the PGo approach works for complex models: we model check, compile, and evaluate the performance of MPCal systems based on Raft, CRDTs, and primary-backup. Compared to previous work, PGo requires less time to develop a checked model and derive a fully working implementation. With PGo we created a formally checked Raft model and its corresponding implementation in under 1 person-month, which is 3x less time than Ivy. Our evaluation shows that a PGo-based Raft KV store with three nodes has 41% higher throughput than a Raft KV store based on Ivy, the highest performing verified Raft-based KV store from related work. A PGo-based CRDT set has a latency within 2x of a CRDT set implementation from SoundCloud called Roshi.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.012 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.012 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".