# 用户:Hengfeng-Wei

## Profile

Hengfeng Wei (魏恒峰)

Institute of Computer Software State Key Laboratory for Novel Software Technology Department of Computer Science and Technology Nanjing University Addr: 163 Xianlin Road, Nanjing 210046, P. R. China

Office: 302

## Researches

I am interested in Distributed Computing Theory and Formal Methods.

## Publications

- RVSI --- Under Review
- PA2AM --- Probabilistically-Atomic 2-Atomicity: Enabling Almost Strong Consistency in Distributed Storage Systems
- VPC --- Verifying Pipelined-RAM Consistency over Read/Write Traces of Data Replicas
- CTL3 --- Formal Specification and Runtime Detection of Temporal Properties for Asynchronous Context

### Probabilistically-Atomic 2-Atomicity: Enabling Almost Strong Consistency in Distributed Storage Systems

Hengfeng Wei, Yu Huang, Jian Lu. Probabilistically-Atomic 2-Atomicity: Enabling Almost Strong Consistency in Distributed Storage Systems. InIEEE Trans. Comput., 66(3):502--514, doi:10.1109/TC.2016.2601322, March 2017. [abstract@IEEE] [Paper: PA2AM@TC'2017] [Paper: PA2AM@arXiv (not up-to-date)]

Last night (2016-10-13), I reread the paper "On Interprocess Communication --- Part II: Algorithms" of Leslie Lamport, and found that in Proposition 5, Lamport has proved that in the single-writer model a regular register is atomic if two successive reads that overlap the same write cannot obtain the new then the old value. The phenomenon that "two successive reads that overlap the same write cannot obtain the new then the old value" is exactly the old-new inversion anomaly. Therefore, Lamport has shown that a regular register is atomic if it does not allow old-new inversion anomalies. This is very similar to Theorem 1 in our paper which essentially states that the PA2AM algorithm implements a 2-atomic register *and* the old-new inversion anomaly is the only cause of atomicity violation.

The major difference between Proposition 5 of Lamport and Theorem 1 in our paper is that Proposition 5 is at the specification level while Theorem 1 is at the implementation level.

Combining Proposition 5 and Theorem 1, we obtain

- Conjecture 1
- In the single-writer model, 2-atomicity is equivalent to regularity.

- Conjecture 2
- In the single-write model, PA2AM implements a regular register.

### Verifying Pipelined-RAM Consistency over Read/Write Traces of Data Replicas

Hengfeng Wei, Marzio De Biasi, Yu Huang, Jiannong Cao, and Jian Lu. Verifying Pipelined-RAM Consistency over Read/Write Traces of Data Replicas. InIEEE Trans. Parallel Distrib. Syst., 27(5):1511--1523, May 2016, doi:10.1109/TPDS.2015.2453985 [abstract@IEEE] [Paper: VPC@TPDS'2016] [Paper: VPC@arXiv(not up-to-date)] SCI: DJ5HS

In the Conclusion section, we discussed the VCC (Verifying Causal Consistency) problem and wrote: "Because Pipelined-RAM is a weakening of causal consistency, our NP-complete result also applies to the general problem of verifying causal consistency".

I am sorry to say that it is not right for us to conclude that VCC, in general, (i.e., VCC-SD in our terms) is NP-complete just because Pipelined-RAM is a weakening of causal consistency.

However, I still believe that VCC-SD is NP-complete and that the basic idea of the polynomial reduction used in the NP-complete proof for VPC-SD will be useful in proving the NP-completeness of VCC-SD.

The NP-completeness proof for VPC-SD (along with VPC-MD) is mainly credited to Marzio De Biasi, the second author of this paper.

### Formal Specification and Runtime Detection of Temporal Properties for Asynchronous Context

Hengfeng Wei, Yu Huang, Jiannong Cao, Xiaoxing Ma, Jian Lu. Formal Specification and Runtime Detection of Temporal Properties for Asynchronous Context. InProceedings of the 10th IEEE International Conference on Pervasive Computing and Communications(IEEE PerCom '12), pages 30--38, 2012.[abstract@IEEE] [Paper: CTL3@PerCom'2012] EI: 20122315082503

## Links

- hengxin@github.io: A blog hosted on GitHub.

- hengxin@StackExchange: My profile on StackExchange --- A wonderful Q/A site.

- hengxin@GitHub: Open source projects.

- hengxin@Bitbucket: Private repositories for unpublished papers and reports.