物件導向軟體之架構(Object-Oriented Software Construction)探討

ing WS1S Systems to Verify Parameterized Networks . . . . . . . . . . . . 188 Kai Baukus, Saddek Bensalem, Yassine Lakhnech and Karsten Stahl FMona: A Tool for Expressing Validation Techniques over Infinite State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 J.-P. Bodeveix and M. Filali Transitive Closures of Regular Relations for Verifying Infinite-State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Bengt Jonsson and Marcus Nilsson Diagnostic and Test Generation Using Static Analysis to Improve Automatic Test Generation . . . . . . . . . . . . . 235 Marius Bozga, Jean-Claude Fernandez and Lucian Ghirvu Efficient Diagnostic Generation for Boolean Equation Systems . . . . . . . . . . . . 251 Radu Mateescu Efficient Model-Checking Compositional State Space Generation with Partial Order Reductions for Asynchronous Communicating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Jean-Pierre Krimm and Laurent Mounier Checking for CFFD-Preorder with Tester Processes . . . . . . . . . . . . . . . . . . . . . . . 283 Juhana Helovuo and Antti Valmari Fair Bisimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Thomas A. Henzinger and Sriram K. Rajamani Integrating Low Level Symmetries into Reachability Analysis . . . . . . . . . . . . . 315 Karsten Schmidt Model-Checking Tools Model Checking Support for the ASM High-Level Language . . . . . . . . . . . . . . 331 Giuseppe Del Castillo and Kirsten Winter Table of

Tools and Algorithms for the Construction and Analysis of Systems. Proc. TACAS 2009

Most high-performance software transactional memories (STM) use optimistic invisible reads. Consequently, a transaction might have an inconsistent view of the objects it accesses unless the consistency of the view is validated whenever the view changes. Although all STMs usually detect inconsistencies at commit time, a transaction might never reach this point because an inconsistent view can provoke arbitrary behavior in the application (e.g., enter an infinite loop). In this paper, we formally introduce a lazy snapshot algorithm that verifies at each object access that the view observed by a transaction is consistent. Validating previously accessed objects is not necessary for that, however, it can be used on-demand to prolong the view's validity. We demonstrate both formally and by measurements that the performance of our approach is quite competitive by comparing other STMs with an STM that uses our algorithm.

https://doc.rero.ch/record/18139/files/Riegel_Torvald_-_A_Lazy_Snapshot_Algorithm_with_Eager_Validation_20100430.pdf

A Lazy Snapshot Algorithm with Eager Validation

The automata-theoretic approach to LTL verification relies on an algorithm for finding accepting cycles in a Biichi automaton. Explicit-state model checkers typically construct the automaton on the fly and explore its states using depth-first search. We survey algorithms proposed for this purpose and identify two good algorithms, a new algorithm based on nested DFS, and another based on strongly connected components. We compare these algorithms both theoretically and experimentally and determine cases where both algorithms can be useful.

A note on on-the-fly verification algorithms

This paper presents Salt, a distributed database that allows developers to improve the performance and scalability of their ACID applications through the incremental adoption of the BASE approach. Salt's motivation is rooted in the Pareto principle: for many applications, the transactions that actually test the performance limits of ACID are few. To leverage this insight, Salt introduces BASE transactions, a new abstraction that encapsulates the workflow of performance-critical transactions. BASE transactions retain desirable properties like atomicity and durability, but, through the new mechanism of Salt Isolation, control which granularity of isolation they offer to other transactions, depending on whether they are BASE or ACID. This flexibility allows BASE transactions to reap the performance benefits of the BASE paradigm without compromising the guarantees enjoyed by the remaining ACID transactions. For example, in our MySQL Cluster-based implementation of Salt, BASE-ifying just one out of 11 transactions in the open source ticketing application Fusion Ticket yields a 6.5x increase over the throughput obtained with an ACID implementation.

Salt: Combining ACID and BASE in a distributed database (invited talk)

Most geo-replicated storage systems use weak consistency to avoid the performance penalty of coordinating replicas in different data centers. This departure from strong semantics poses problems to application programmers, who need to address the anomalies enabled by weak consistency. In this paper we use a recently proposed isolation level, called Non-Monotonic Snapshot Isolation, to achieve ACID transactions with low latency. To this end, we present Blotter, a geo-replicated system that leverages these semantics in the design of a new concurrency control protocol that leaves a small amount of local state during reads to make commits more efficient, which is combined with a configuration of Paxos that is tailored for good performance in wide area settings. Read operations always run on the local data center, and update transactions complete in a small number of message steps to a subset of the replicas. We implemented Blotter as an extension to Cassandra. Our experimental evaluation shows that Blotter has a small overhead at the data center scale, and performs better across data centers when compared with our implementations of the core Spanner protocol and of Snapshot Isolation on the same codebase.

Blotter: Low Latency Transactions for Geo-Replicated Storage

Transactional memory is a new trend in concurrency control that was boosted by the advent of multi-core processors and the near to come many-core processors. It promises the performance of finer grain with the simplicity of coarse grain threading. However, there is a clear absence of software development tools oriented to the transactional memory programming model, which is confirmed by the very small number of related scientific works published until now.This paper describes ongoing work. We propose a very low overhead monitoring framework, developed specifically for monitoring TM computations, that collects the transactional events into a single log file, sorted in a global order. This framework is then used by a visualization tool to display different types of charts from two categories: statistical charts and thread-time space diagrams. These last diagrams are interactive, allowing to identify conflicting transactions. We use the visualization tool to analyse the behavior of two different, but similar, testing applications, illustrating how it can be used to better understand the behavior of these transactional memory applications.

Understanding the behavior of transactional memory applications

Concurrent programs that are free of unsynchronized accesses to shared data may still exhibit unpredictable concurrency errors, called atomicity violations, which include both high-level data races and stale-value errors. Atomicity violations occur when programmers make wrong assumptions about the atomicity scope of a code block, incorrectly splitting it in two or more atomic blocks and allowing them to be interleaved with other atomic blocks. In this paper we propose a novel static analysis algorithm that works on a dependency graph of program variables and detects both high-level data races and stale-value errors. The algorithm was implemented for a Java Bytecode analyzer and its effectiveness was evaluated with well known faulty programs. The results obtained show that our algorithm performs better than previous approaches, achieving higher precision for small and medium sized programs, making it a good basis for a practical tool.

/pdf/precise-detection-of-atomicity-violations-2v44druwmm.pdf

Precise detection of atomicity violations

The use of the Snapshot Isolation (SI) level in Transactional Memory (TM) eliminates the need of tracking memory read accesses, reducing the run-time overhead and fastening the commit phase. By detecting only write-write conflicts, SI allows many memory transactions to succeed that would otherwise abort if serialized. This higher commit rate comes at the expense of introducing anomalous behaviors by allowing some real conflicting transactions to commit. We aim at improving the performance of TM systems by running programs under SI, while guaranteeing a serializable semantics. This is achieved by static analysis of TM programs using Separation Logic to detect possible anomalies when running under SI. To guarantee correct behavior, the program code can be automatically modified to avoid these anomalies. Our approach can have an important impact on the performance of single multi-core node TM systems, and also of distributed TM systems by considerable reducing the required network traffic.

Efficient and Correct Transactional Memory Programs Combining Snapshot Isolation and Static Analysis

Transactional memory systems providing snapshot isolation enable concurrent access to shared data without incurring aborts on read-write conflicts. Reducing aborts is extremely relevant as it leads to higher concurrency, greater performance, and better predictability. Unfortunately, snapshot isolation does not provide serializability as it allows certain anomalies that can lead to subtle consistency violations. While some mechanisms have been proposed to verify the correctness of a program utilizing snapshot isolation transactions, it remains difficult to repair incorrect applications. To reduce the programmer’s burden in this case, we present a technique based on dynamic code and graph dependency analysis that automatically corrects existing snapshot isolation anomalies in transactional memory programs. Our evaluation shows that corrected applications retain the performance benefits characteristic of snapshot isolation over conventional transactional memory systems.

https://dl.acm.org/doi/pdf/10.1145/2693260

Ricardo J. Dias

Papers

Blotter: Low Latency Transactions for Geo-Replicated Storage

Understanding the behavior of transactional memory applications

Precise detection of atomicity violations

Efficient and Correct Transactional Memory Programs Combining Snapshot Isolation and Static Analysis

Efficient Correction of Anomalies in Snapshot Isolation Transactions