Message-passing code generation for non-rectangular tiling transformations

Goumas, Georgios; Drosinos, Nikolaos; Athanasaki, Maria; Koziris, Nectarios

doi:10.1016/j.parco.2006.07.003

Cited by 5 publications

(10 citation statements)

References 23 publications

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“…These methods [22,9,4,15] require not only footprint calculations for each tile but also the intersection of footprints with data tiles. As described in detail in Section 1, calculating such intersections is very complex, which explains the complexity and simplifying limitations of many existing methods.…”

Section: Related Workmentioning

confidence: 99%

“…However, it is the message aggregation calculation that defies easy mathematical characterization for the general case of affine accesses. Instead some very complex research methods [9,22] have been devised that make many simplifying assumptions on the types of affine accesses supported, and yet remain so complex that they are rarely implemented in production compilers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Affine Loop Optimization Based on Modulo Unrolling in Chapel

Sharma

Smith

Koehler

et al. 2014

Proceedings of the 8th International Conference on Partitioned Global Address Space Programming Models

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This paper presents modulo unrolling without unrolling (modulo unrolling WU), a method for message aggregation for parallel loops in message passing programs that use affine array accesses in Chapel, a Partitioned Global Address Space (PGAS) parallel programming language. Messages incur a non-trivial run time overhead, a significant component of which is independent of the size of the message. Therefore, aggregating messages improves performance. Our optimization for message aggregation is based on a technique known as modulo unrolling, pioneered by Barua [3], whose purpose was to ensure a statically predictable single tile number for each memory reference for tiled architectures, such as the MIT Raw Machine [18]. Modulo unrolling WU applies to data that is distributed in a cyclic or block-cyclic manner. In this paper, we adapt the aforementioned modulo unrolling technique to the difficult problem of efficiently compiling PGAS languages to message passing architectures. When applied to loops and data distributed cyclically or blockcyclically, modulo unrolling WU can decide when to aggregate messages thereby reducing the overall message count and runtime for a particular loop. Compared to other methods, modulo unrolling WU greatly simplifies the complex problem of automatic code generation of message passing code. It also results in substantial performance improvement compared to the non-optimized Chapel compiler.To implement this optimization in Chapel, we modify the leader and follower iterators in the Cyclic and Block Cyclic data distribution modules. Results were collected that compare the performance of Chapel programs optimized with modulo unrolling WU and Chapel programs using the existing Chapel data distributions. Data collected on a tenlocale cluster show that on average, modulo unrolling WU used with Chapel's Cyclic distribution results in 64 percent fewer messages and a 36 percent decrease in runtime for our suite of benchmarks. Similarly, modulo unrolling WU used with Chapel's Block Cyclic distribution results in 72 percent fewer messages and a 53 percent decrease in runtime.

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Section: Related Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Affine Loop Optimization Based on Modulo Unrolling in Chapel

Sharma

Smith

Koehler

et al. 2014

Proceedings of the 8th International Conference on Partitioned Global Address Space Programming Models

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“…The problem of the application of general tiling transformations has been attacked in [1] and [2], where it is shown that the general case can be handled only by an automatic parallelizing compiler. However, the problem of efficiently mapping non-rectangular tiles to a fixed number of processes is still open.…”

Section: Introductionmentioning

confidence: 99%

Coarse-grain Parallel Execution for 2-dimensional PDE Problems

Goumas

Drosinos

Karakasis

et al. 2007

2007 IEEE International Parallel and Distributed Processing Symposium

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“…Hodzic et al in [10] propose a new framework of defining tiling parameters for an arbitrary iteration space with dependences based upon minimizing theoretical execution time. Goumas et al in [9] propose efficient code generation algorithms for tiled iteration spaces in message passing distributed systems. There exists a lot of work in the area of scheduling for parallel computing as well.…”

mentioning

confidence: 99%

“…Assuming that n 2 (j) is known we want to find the value of n 2 (j + 1) that minimizes the function in (9). Using differentiation of function C(x, y) for variable x and solving the equation dC(x, y)/dx = 0 for y, we determine that:…”

mentioning

confidence: 99%

An optimal scheduling scheme for tiling in distributed systems

Kyriakopoulos

Chronopoulos

2007

2007 IEEE International Conference on Cluster Computing

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Abstract-There exist several scheduling schemes for parallelizing loops without dependences for shared and distributed memory systems. However, efficiently parallelizing loops with dependences is a more complicated task. This becomes even more difficult when the loops are executed on a distributed memory cluster where communication and synchronization can be a bottleneck. The problem lies in the processor idle time which occurs during the beginning and final stages of the execution. In this paper we propose a new scheduling scheme that minimizes the processor idle time and thus it enhances load balancing and performance. The new scheme is applied to two-dimensional iteration spaces with dependences. The proposed scheduling scheme follows a tiled wavefront pattern in which the tile size gradually decreases in all dimensions. We have tested the proposed scheme on a dedicated and homogeneous cluster of workstations and we verified that it significantly improves execution times over scheduling using traditional tiling.

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Message-passing code generation for non-rectangular tiling transformations

Cited by 5 publications

References 23 publications

Affine Loop Optimization Based on Modulo Unrolling in Chapel

Affine Loop Optimization Based on Modulo Unrolling in Chapel

Coarse-grain Parallel Execution for 2-dimensional PDE Problems

An optimal scheduling scheme for tiling in distributed systems

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