An atomic model for message-passing

Liu, Pangfeng; Aiello, William; Bhatt, Sandeep N.

doi:10.1145/165231.165251

Cited by 38 publications

(15 citation statements)

References 4 publications

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“…The LogP model permits general asynchronous algorithms. Liu, Aiello, and Bhatt [47] studied a message-passing model in which messages destined for the same processor are serviced one at a time in an arbitrary order. Their model permits general asynchronous algorithms, but each processor can have at most one message outstanding at a time.…”

Section: Related Workmentioning

confidence: 99%

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The Queue-Read Queue-Write PRAM Model: Accounting for Contention in Parallel Algorithms

Gibbons¹,

Matias²,

Ramachandran³

1998

SIAM J. Comput.

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Abstract. This paper introduces the queue-read queue-write (qrqw) parallel random access machine (pram) model, which permits concurrent reading and writing to shared-memory locations, but at a cost proportional to the number of readers/writers to any one memory location in a given step. Prior to this work there were no formal complexity models that accounted for the contention to memory locations, despite its large impact on the performance of parallel programs. The qrqw pram model reflects the contention properties of most commercially available parallel machines more accurately than either the well-studied crcw pram or erew pram models: the crcw model does not adequately penalize algorithms with high contention to shared-memory locations, while the erew model is too strict in its insistence on zero contention at each step.The qrqw pram is strictly more powerful than the erew pram. This paper shows a separation of log n between the two models, and presents faster and more efficient qrqw algorithms for several basic problems, such as linear compaction, leader election, and processor allocation. Furthermore, we present a work-preserving emulation of the qrqw pram with only logarithmic slowdown on Valiant's bsp model, and hence on hypercube-type noncombining networks, even when latency, synchronization, and memory granularity overheads are taken into account. This matches the bestknown emulation result for the erew pram, and considerably improves upon the best-known efficient emulation for the crcw pram on such networks. Finally, the paper presents several lower bound results for this model, including lower bounds on the time required for broadcasting and for leader election.Key words. models of parallel computation, parallel algorithms, pram, memory contention, work-time framework AMS subject classifications. 68Q05, 68Q22, 68Q25PII. S009753979427491 1. Introduction. The parallel random access machine (pram) model of computation is the most-widely used model for the design and analysis of parallel algorithms (see, e.g., [40,39,58]). The pram model consists of a number of processors operating in lock-step and communicating by reading and writing locations in a shared memory. Existing pram models can be distinguished by their rules regarding contention for shared memory locations. These rules are generally classified into two groups:• Exclusive read/write: Each location can be read or written by at most one processor in each unit-time pram step.• Concurrent read/write: Each location can be read or written by any number of processors in each unit-time pram step. For concurrent writing, the value written depends on the write-conflict rule of the model, e.g., in the arbitrary concurrent-write pram, an arbitrary processor succeeds in writing its value.

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Section: Related Workmentioning

confidence: 99%

“…Unlike each of these models, the qrqw pram does not explicitly limit the number of outstanding requests. The simd-qrqw pram, on the other hand, has the same restriction as the Liu, Aiello, and Bhatt [47] and Dwork, Herlihy, and Waarts [19] models, namely, one request per processor.…”

Section: Related Workmentioning

confidence: 99%

The Queue-Read Queue-Write PRAM Model: Accounting for Contention in Parallel Algorithms

Gibbons¹,

Matias²,

Ramachandran³

1998

SIAM J. Comput.

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“…Our strategy is to mimic the theorems of [4] for a more restricted model of multithreaded computation. As in [4], the bounds assume a communication model in which messages are delayed only by contention at destination processors, but no assumptions are made about the order in which contending messages are delivered [33]. For technical reasons in our analysis of execution time, the critical path is calculated assuming that all threads spawned by a parent thread are spawned at the end of the parent thread.…”

Section: Proofmentioning

confidence: 99%

Cilk: An Efficient Multithreaded Runtime System

Blumofe¹,

Joerg²,

Kuszmaul³

et al. 1996

Journal of Parallel and Distributed Computing

938

924

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Cilk (pronounced "silk") is a C-based runtime system for multithreaded parallel programming. In this paper, we document the efficiency of the Cilk work-stealing scheduler, both empirically and analytically. We show that on real and synthetic applications, the "work" and "critical-path length" of a Cilk computation can be used to model performance accurately. Consequently, a Cilk programmer can focus on reducing the computation' s work and critical-path length, insulated from load balancing and other runtime scheduling issues. We also prove that for the class of "fully strict" (well-structured) programs, the Cilk scheduler achieves space, time, and communication bounds all within a constant factor of optimal.The Cilk runtime system currently runs on the Connection Machine CM5 MPP, the Intel Paragon MPP, the Sun Sparcstation SMP, and the Cilk-NOW network of workstations. Applications written in Cilk include protein folding, graphic rendering, backtrack search, and the ?Socrates chess program, which won second prize in the 1995 World Computer Chess Championship.

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“…For example, sending messages in order of increasing destination address gives low throughput, since virtual channels to the same receiver are blocked. In an earlier paper [18], we developed the atomic message model to investigate this phenomenon. Consistent with the theory, we find that sending messages in random order worked best.…”

Section: Reducing Communication Timesmentioning

confidence: 99%

Experiences with parallel N-body simulation

Liu

Bhatt

1994

Proceedings of the Sixth Annual ACM Symposium on Parallel Algorithms and Architectures - SPAA '94

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AbstractÐThis paper describes our experiences developing high-performance code for astrophysical N-body simulations. Recent N-body methods are based on an adaptive tree structure. The tree must be built and maintained across physically distributed memory; moreover, the communication requirements are irregular and adaptive. Together with the need to balance the computational work-load among processors, these issues pose interesting challenges and tradeoffs for high-performance implementation. Our implementation was guided by the need to keep solutions simple and general. We use a technique for implicitly representing a dynamic global tree across multiple processors which substantially reduces the programming complexity as well as the performance overheads of distributed memory architectures. The contributions include methods to vectorize the computation and minimize communication time which are theoretically and experimentally justified. The code has been tested by varying the number and distribution of bodies on different configurations of the Connection Machine CM-5. The overall performance on instances with 10 million bodies is typically over 48 percent of the peak machine rate, which compares favorably with other approaches.Index TermsÐN-body simulations, parallel processing, Barnes-Hut algorithm, adaptive tree structure, Peano-Hilbert space filling curve.

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An atomic model for message-passing

Cited by 38 publications

References 4 publications

The Queue-Read Queue-Write PRAM Model: Accounting for Contention in Parallel Algorithms

The Queue-Read Queue-Write PRAM Model: Accounting for Contention in Parallel Algorithms

Cilk: An Efficient Multithreaded Runtime System

Experiences with parallel N-body simulation

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