On the complexity of checking transactional consistency

Biswas, Ranadeep; Enea, Constantin

doi:10.1145/3360591

Cited by 32 publications

(62 citation statements)

References 17 publications

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“…An algorithm similar to Algorithm 3 has been developed independently by Biswas and Enea [2019] for checking serializability of bounded-width histories. Their result also implies that checking sequential consistency of histories with a bounded number of threads is polynomial time.…”

Section: Related Workmentioning

confidence: 99%

Optimal stateless model checking for reads-from equivalence under sequential consistency

Abdulla

Atig

Jönsson

et al. 2019

Proc. ACM Program. Lang.

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We present a new approach for stateless model checking (SMC) of multithreaded programs under Sequential Consistency (SC) semantics. To combat state-space explosion, SMC is often equipped with a partial-order reduction technique, which defines an equivalence on executions, and only needs to explore one execution in each equivalence class. Recently, it has been observed that the commonly used equivalence of Mazurkiewicz traces can be coarsened but still cover all program crashes and assertion violations. However, for this coarser equivalence, which preserves only the reads-from relation from writes to reads, there is no SMC algorithm which is (i) optimal in the sense that it explores precisely one execution in each reads-from equivalence class, and (ii) efficient in the sense that it spends polynomial effort per class. We present the first SMC algorithm for SC that is both optimal and efficient in practice, meaning that it spends polynomial time per equivalence class on all programs that we have tried. This is achieved by a novel test that checks whether a given reads-from relation can arise in some execution. We have implemented the algorithm by extending Nidhugg, an SMC tool for C/C++ programs, with a new mode called rfsc. Our experimental results show that Nidhugg/rfsc, although slower than the fastest SMC tools in programs where tools happen to examine the same number of executions, always scales similarly or better than them, and outperforms them by an exponential factor in programs where the reads-from equivalence is coarser than the standard one. We also present two non-trivial use cases where the new equivalence is particularly effective, as well as the significant performance advantage that Nidhugg/rfsc offers compared to state-of-the-art SMC and systematic concurrency testing tools. CCS Concepts: • Software and its engineering → Software verification and validation; • Theory of computation → Verification by model checking.

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Section: Related Workmentioning

confidence: 99%

Optimal stateless model checking for reads-from equivalence under sequential consistency

Abdulla

Atig

Jönsson

et al. 2019

Proc. ACM Program. Lang.

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“…an operational semantics), which does not apply in our case. The relationship between PC and SER is similar in spirit to the one given by Biswas and Enea [14] in the context of checking whether an execution is PC. However, that relationship was proven in the context of a "weaker" notion of trace (containing only program order and read-from), and it does not extend to our notion of trace.…”

Section: Related Workmentioning

confidence: 68%

“…The consistency models in this paper were studied in several recent works [21,20,25,43,16,44,14]. Most of them focused on their operational and axiomatic formalizations.…”

Section: Related Workmentioning

confidence: 99%

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Checking Robustness Between Weak Transactional Consistency Models

Bouajjani

Enea

2021

Programming Languages and Systems

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Concurrent accesses to databases are typically encapsulated in transactions in order to enable isolation from other concurrent computations and resilience to failures. Modern databases provide transactions with various semantics corresponding to different trade-offs between consistency and availability. Since a weaker consistency model provides better performance, an important issue is investigating the weakest level of consistency needed by a given program (to satisfy its specification). As a way of dealing with this issue, we investigate the problem of checking whether a given program has the same set of behaviors when replacing a consistency model with a weaker one. This property known as robustness generally implies that any specification of the program is preserved when weakening the consistency. We focus on the robustness problem for consistency models which are weaker than standard serializability, namely, causal consistency, prefix consistency, and snapshot isolation. We show that checking robustness between these models is polynomial time reducible to a state reachability problem under serializability. We use this reduction to also derive a pragmatic proof technique based on Lipton’s reduction theory that allows to prove programs robust. We have applied our techniques to several challenging applications drawn from the literature of distributed systems and databases.

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“…(1) We present an algorithm that solves VTSO-rf in 𝑂 (𝑘 • 𝑛 𝑘+1 ) time. The case of VSC-rf is solvable in 𝑂 (𝑘 • 𝑛 𝑘 ) time [Abdulla et al 2019;Biswas and Enea 2019;Mathur et al 2020]. Although for TSO there are 𝑘 additional buffers, our result shows that the complexity is only minorly impacted by an additional factor 𝑛, as opposed to 𝑛 𝑘 .…”

Section: Our Contributionsmentioning

confidence: 83%

The reads-from equivalence for the TSO and PSO memory models

Bui

Chatterjee

Gautam

et al. 2021

Proc. ACM Program. Lang.

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The verification of concurrent programs remains an open challenge due to the non-determinism in inter-process communication. One recurring algorithmic problem in this challenge is the consistency verification of concurrent executions. In particular, consistency verification under a reads-from map allows to compute the reads-from (RF) equivalence between concurrent traces, with direct applications to areas such as Stateless Model Checking (SMC). Importantly, the RF equivalence was recently shown to be coarser than the standard Mazurkiewicz equivalence, leading to impressive scalability improvements for SMC under SC (sequential consistency). However, for the relaxed memory models of TSO and PSO (total/partial store order), the algorithmic problem of deciding the RF equivalence, as well as its impact on SMC, has been elusive. In this work we solve the algorithmic problem of consistency verification for the TSO and PSO memory models given a reads-from map, denoted VTSO-rf and VPSO-rf, respectively. For an execution of n events over k threads and d variables, we establish novel bounds that scale as n k +1 for TSO and as n k +1 · min( n k 2 , 2 k · d ) for PSO. Moreover, based on our solution to these problems, we develop an SMC algorithm under TSO and PSO that uses the RF equivalence. The algorithm is exploration-optimal , in the sense that it is guaranteed to explore each class of the RF partitioning exactly once, and spends polynomial time per class when k is bounded. Finally, we implement all our algorithms in the SMC tool Nidhugg, and perform a large number of experiments over benchmarks from existing literature. Our experimental results show that our algorithms for VTSO-rf and VPSO-rf provide significant scalability improvements over standard alternatives. Moreover, when used for SMC, the RF partitioning is often much coarser than the standard Shasha-Snir partitioning for TSO/PSO, which yields a significant speedup in the model checking task.

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On the complexity of checking transactional consistency

Cited by 32 publications

References 17 publications

Optimal stateless model checking for reads-from equivalence under sequential consistency

Optimal stateless model checking for reads-from equivalence under sequential consistency

Checking Robustness Between Weak Transactional Consistency Models

The reads-from equivalence for the TSO and PSO memory models

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