SC12 Home > SC12 Schedule > SC12 Presentation - Tiling Stencil Computations to Maximize Parallelism

SCHEDULE: NOV 10-16, 2012

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Tiling Stencil Computations to Maximize Parallelism

SESSION: Compiler-Based Analysis and Optimization

EVENT TYPE: Papers

TIME: 11:00AM - 11:30AM

SESSION CHAIR: Xipeng Shen

AUTHOR(S):Vinayaka Bandishti, Irshad Pananilath, Uday Bondhugula

ROOM:255-EF

ABSTRACT:
Most stencil computations allow tile-wise concurrent start, i.e., there always exists a face of the iteration space and a set of tiling hyperplanes such that all tiles along that face can be started concurrently. This provides load balance and maximizes parallelism. However, existing automatic tiling frameworks often choose hyperplanes that lead to pipelined start-up and load imbalance. We address this issue with a new tiling technique that ensures concurrent start-up as well as perfect load-balance whenever possible. We first provide necessary and sufficient conditions on tiling hyperplanes to enable concurrent start for programs with affine data accesses. We then provide an approach to find such hyperplanes. Experimental evaluation on a 12-core Intel Westmere shows that our code is able to outperform a tuned domain-specific stencil code generator by 4 to 20 percent, and previous compiler techniques by a factor of 2x to 10.14x.

Chair/Author Details:

Xipeng Shen (Chair) - College of William and Mary

Vinayaka Bandishti - Indian Institute of Science

Irshad Pananilath - Indian Institute of Science

Uday Bondhugula - Indian Institute of Science

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Tiling Stencil Computations to Maximize Parallelism

SESSION: Compiler-Based Analysis and Optimization

EVENT TYPE:

TIME: 11:00AM - 11:30AM

SESSION CHAIR: Xipeng Shen

AUTHOR(S):Vinayaka Bandishti, Irshad Pananilath, Uday Bondhugula

ROOM:255-EF

ABSTRACT:
Most stencil computations allow tile-wise concurrent start, i.e., there always exists a face of the iteration space and a set of tiling hyperplanes such that all tiles along that face can be started concurrently. This provides load balance and maximizes parallelism. However, existing automatic tiling frameworks often choose hyperplanes that lead to pipelined start-up and load imbalance. We address this issue with a new tiling technique that ensures concurrent start-up as well as perfect load-balance whenever possible. We first provide necessary and sufficient conditions on tiling hyperplanes to enable concurrent start for programs with affine data accesses. We then provide an approach to find such hyperplanes. Experimental evaluation on a 12-core Intel Westmere shows that our code is able to outperform a tuned domain-specific stencil code generator by 4 to 20 percent, and previous compiler techniques by a factor of 2x to 10.14x.

Chair/Author Details:

Xipeng Shen (Chair) - College of William and Mary

Vinayaka Bandishti - Indian Institute of Science

Irshad Pananilath - Indian Institute of Science

Uday Bondhugula - Indian Institute of Science

Add to iCal  Click here to download .ics calendar file

Add to Outlook  Click here to download .vcs calendar file

Add to Google Calendarss  Click here to add event to your Google Calendar