ATI Stream Computing OpenCL Programming Guide - CiteSeerX

ATI STREAM COMPUTINGNDRangeGlobal Domain xget_global_size(0)Work-GroupWork-Group Id = (Bx, By)Global Domain yget_global_size(0)Work-Group1Work-Group2Work-GroupWork-Group Work-Group Work-GroupWork-Group Work-Group Work-GroupnWavefront1WavefrontWavefront2WavefrontWavefrontWavefrontWavefront Wavefront Wavefrontnget_group_size(1)WavefrontWork-ItemWork-Item. . .W-Iid = (0,0) W-Iid = (Gx - 1,0)globalid =globalid =(Bx*Gx, By*Gy) (Bx*Gx + Gx-1, By*Gy). . .. . .. . .Work-Group Size Gyget_group_size(0)Work-Group Size GxWork-ItemW-Iid = (0,Gy-1). . .Work-ItemW-Iid = (Gx-1, Gy-1)globalid = globalid =(Bx*Gx, By*Gy + Gy-1)(Bx*Gx+Gx-1,By*Gy+Gy-1)Figure 1.5Work-Item Grouping Into Work-Groups and Wavefronts1.3.1 Work-Item ProcessingAll stream cores within a compute unit execute the same instruction for eachcycle. A work item can issue one VLIW instruction per clock cycle. The block ofwork-items that are executed together is called a wavefront. To hide latenciesdue to memory accesses and processing element operations, up to four workitemsfrom the same wavefront are pipelined on the same stream core. For1.3 The ATI Stream Computing Implementation of OpenCL 1-7Copyright © 2010 Advanced Micro Devices, Inc. All rights reserved.