mit-pdos/perennial
Oct 2024 – May 2025
7 Months active
Languages Used
CoqGoVShellGooseVerilog
Technical Skills
Concurrency ControlDistributed SystemsFormal VerificationProof EngineeringSystem DesignConcurrency
Yun-Sheng Chang
PROFILE
Yun-sheng Chang
Yifan Chang worked on the mit-pdos/perennial repository, building and formally verifying distributed backup and consensus protocols for the Tulip system. Using Coq and Go, Yifan engineered robust backup coordination, crash recovery, and transaction management layers, focusing on correctness through formal proofs and invariants. The work included protocol design, serialization, and concurrency control, with enhancements to state reconstruction, logging, and operational tooling. By integrating group-aware consensus and refining backup interval logic, Yifan improved reliability and maintainability. Code analysis scripts and theorem refactoring further strengthened codebase visibility and correctness, demonstrating deep engagement with distributed systems and formal verification methodologies.
Overall Statistics
Feature vs Bugs
92%Features
Repository Contributions
84Total
Bugs
2
Commits
84
Features
23
Lines of code
72,602
Activity Months7
Your Network
112 people
Work History
May 2025
1 Commits • 1 Features
May 1, 2025May 2025 monthly summary for mit-pdos/perennial focusing on delivering measurable improvements in code visibility and formalization of transaction behavior. The work aligns with business goals of better budgeting for code size, clearer tech debt signals, and stronger correctness guarantees for Tulip-system operations.
1 Commits • 1 Features
May 1, 2025May 2025 monthly summary for mit-pdos/perennial focusing on delivering measurable improvements in code visibility and formalization of transaction behavior. The work aligns with business goals of better budgeting for code size, clearer tech debt signals, and stronger correctness guarantees for Tulip-system operations.
May 2025
April 2025
15 Commits • 4 Features
Apr 1, 2025April 2025 focused on formal verification and reliability hardening for the mit-pdos/perennial backup subsystem (Tulip). Delivered end-to-end formal proofs for backup transaction coordination and backup group coordination, along with initialization and checkpointing groundwork, and improvements to ranking and encoding/decoding flows. Implemented tie-breaking fixes and cleanup of unused components to strengthen system reliability. Hardened inter-coordinator messaging through proofs for replica inquiries and backup group coordinator inquiries, including correct encoding/decoding and robust communication. Completed commit/abort proofs for the backup transaction coordinator, with refactoring to ensure correct timestamp propagation and coordinator behavior. Introduced a replica backup interval with rank invariants, including non-zero rank in the rank table, to support robust replica backup operation. Lifecycle hardening included concluding and destructing backup coordinators and stabilizing build issues. These efforts collectively improve backup reliability, correctness guarantees, recovery safety, and the foundation for future resilience work.
April 2025
15 Commits • 4 Features
Apr 1, 2025April 2025 focused on formal verification and reliability hardening for the mit-pdos/perennial backup subsystem (Tulip). Delivered end-to-end formal proofs for backup transaction coordination and backup group coordination, along with initialization and checkpointing groundwork, and improvements to ranking and encoding/decoding flows. Implemented tie-breaking fixes and cleanup of unused components to strengthen system reliability. Hardened inter-coordinator messaging through proofs for replica inquiries and backup group coordinator inquiries, including correct encoding/decoding and robust communication. Completed commit/abort proofs for the backup transaction coordinator, with refactoring to ensure correct timestamp propagation and coordinator behavior. Introduced a replica backup interval with rank invariants, including non-zero rank in the rank table, to support robust replica backup operation. Lifecycle hardening included concluding and destructing backup coordinators and stabilizing build issues. These efforts collectively improve backup reliability, correctness guarantees, recovery safety, and the foundation for future resilience work.
March 2025
2 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary for mit-pdos/perennial: Delivered critical backup coordination enhancements with participant groups integration and formal proofs of backup coordinator correctness, strengthening reliability and group-aware consensus in Tulip backups. No major bugs fixed this month; the focus was on reliability, correctness, and architectural clarity to enable safer, scalable backups.
2 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary for mit-pdos/perennial: Delivered critical backup coordination enhancements with participant groups integration and formal proofs of backup coordinator correctness, strengthening reliability and group-aware consensus in Tulip backups. No major bugs fixed this month; the focus was on reliability, correctness, and architectural clarity to enable safer, scalable backups.
March 2025
February 2025
5 Commits • 2 Features
Feb 1, 2025February 2025 (mit-pdos/perennial): Focused on reliability, correctness, and operational readiness of the Paxos-based storage and Tulip replica layers. Delivered crash-recovery improvements, stronger state reconstruction, and better logging, resulting in more robust recovery workflows and reduced downtime. The work also includes refactors and formal invariants to improve maintainability and future extensibility.
February 2025
5 Commits • 2 Features
Feb 1, 2025February 2025 (mit-pdos/perennial): Focused on reliability, correctness, and operational readiness of the Paxos-based storage and Tulip replica layers. Delivered crash-recovery improvements, stronger state reconstruction, and better logging, resulting in more robust recovery workflows and reduced downtime. The work also includes refactors and formal invariants to improve maintainability and future extensibility.
December 2024
15 Commits • 2 Features
Dec 1, 2024Month: 2024-12 — mit-pdos/perennial: Tulip formal verification and operational tooling improvements. Delivered two major feature areas: (1) Tulip Formal Verification Suite for Consensus, RA, and Transactions; (2) Operational Tooling and Debugging Enhancements. Key outcomes include consolidated and proven properties for Paxos-like consensus, resource allocation, logs, and transaction initialization, plus improved debugging and maintenance support through new leader-change handling for commits/aborts and a codebase analysis script. These efforts strengthen correctness, robustness, and maintainability of the distributed stack, enabling safer deployments and easier future evolution.
15 Commits • 2 Features
Dec 1, 2024Month: 2024-12 — mit-pdos/perennial: Tulip formal verification and operational tooling improvements. Delivered two major feature areas: (1) Tulip Formal Verification Suite for Consensus, RA, and Transactions; (2) Operational Tooling and Debugging Enhancements. Key outcomes include consolidated and proven properties for Paxos-like consensus, resource allocation, logs, and transaction initialization, plus improved debugging and maintenance support through new leader-change handling for commits/aborts and a codebase analysis script. These efforts strengthen correctness, robustness, and maintainability of the distributed stack, enabling safer deployments and easier future evolution.
December 2024
November 2024
41 Commits • 12 Features
Nov 1, 2024November 2024 monthly summary for mit-pdos/perennial focused on delivering formal correctness guarantees, stability improvements, and maintainability enhancements for the distributed protocol. Work emphasized FPaxos-based stability integration, end-to-end protocol proofs, and encoding/decoding lemmas, complemented by essential CI fixes and targeted maintenance to stabilize ongoing verification efforts.
November 2024
41 Commits • 12 Features
Nov 1, 2024November 2024 monthly summary for mit-pdos/perennial focused on delivering formal correctness guarantees, stability improvements, and maintainability enhancements for the distributed protocol. Work emphasized FPaxos-based stability integration, end-to-end protocol proofs, and encoding/decoding lemmas, complemented by essential CI fixes and targeted maintenance to stabilize ongoing verification efforts.
October 2024
5 Commits • 1 Features
Oct 1, 2024October 2024: Focused on strengthening the correctness and stability of replica state handling in mit-pdos/perennial through formal invariant proofs and validation improvements. The work reduces risk of replication inconsistencies and prepares the ground for future features by improving proof stability and overall system reliability.
5 Commits • 1 Features
Oct 1, 2024October 2024: Focused on strengthening the correctness and stability of replica state handling in mit-pdos/perennial through formal invariant proofs and validation improvements. The work reduces risk of replication inconsistencies and prepares the ground for future features by improving proof stability and overall system reliability.
October 2024
Activity
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Quality Metrics
Correctness95.4%
Maintainability84.8%
Architecture89.6%
Performance71.6%
AI Usage20.2%
Skills & Technologies
Programming Languages
CoqGoGooseShellVVerilog
Technical Skills
Algorithm ProofsBackup SystemsBackup and RecoveryCode AnalysisConcurrencyConcurrency ControlConsensus AlgorithmsConsensus ProtocolsCrash Fault ToleranceCrash RecoveryData SerializationData StructuresDistributed SystemsFault ToleranceFormal Verification
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