Dynamic SIMD Re-convergence with Paired-Path Comparison

  • 黃 昀棨

Student thesis: Master's Thesis


SIMD divergence is one of the critical causes that decrease the parallel computing efficiency in contemporary GPGPU (General Purpose Graphic Processor Unit) architecture In this thesis we evaluate a cycle accurate GPU simulator platform based on HSAIL under OpenCL framework by offloading the kernel programs into simulator A wavefront (“wavefront” and “warp” in AMD and NVIDIA terminology respectively) is the gathering of multiple threads that execute the same instruction in SIMD fashion When a wavefront or a warp executes a conditional branch instruction threads in the warp may go to distinct PCs if the threads have different branch targets and it’s called SIMD control divergence Re-convergence mechanisms are applied to help divergent wavefront to execute instructions properly We develop a new dynamic stack-based re-convergence scheme that can be implemented with or without finalizer generated re-convergence instructions Using the scheme we propose the divergent warp re-converges dynamically and get a 13 36% activity factor improvement on average from opportunistic early re-convergence in the unstructured control flow and the performance is better in the way that warp re-convergence without finalier generated hint instructions
Date of Award2015 Aug 14
Original languageEnglish
SupervisorChung-Ho Chen (Supervisor)

Cite this