In cache based multiprocessors a protocol must maintain coherence among replicated copies of shared writable data. In delayed consistency protocols the effect of out-going and in-coming invalidations or updates are delayed. Delayed coherence can reduce processor blocking time as well as the effects of false sharing. In this paper, we introduce several implementations of delayed consistency for cache-based systems in the framework of a weaklyordered consistency model. A performance comparison of the delayed protocols with the corresponding On-the-Fly (non-del~ed) consistency protocol is made, through execution-driven simulations of four parallel algorithms. The results show that, for parallel programs in which false sharing is a problem, signljlcant reductions in the data miss rate of parallel programs can be obtained with just a small increase in the cost and complexity of the cache system.

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A new approach in which stateful computations can be performed within the framework of a functional programming language is presented in this papel: In most functionalprogramming languages, programmers are unable to easily manipulate state-based computations which are not supported by functional languages. To solve this problem, we propose to extend the Sisal language with special userdeclared variables. This approach can greatly help users in writing programs, simplifying parallel compilation, and improving performance. Under this scheme, programmers are able to manipulate stateful computations. In our methodology, programmers are allowed to declare special variables, and the parallel threads can be identiJied according to the usage of special variables. In comparison to "pure '' functional languages, the extended Sisal has more expressive power due to the availability of stateful computations.