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DTSTART;TZID=America/Chicago:20181111T145600
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UID:submissions.supercomputing.org_SC18_sess160_ws_whpc117@linklings.com
SUMMARY:Challenges of Performance Portability for Fortran Unstructured Mes
 h Codes
DESCRIPTION:Abigail Hsu (Stony Brook University, Los Alamos National Labor
 atory) and David H. Neill Asanza (Grinnell College, Los Alamos National La
 boratory)\n\nWhat pathways exist for Fortran performance portability to ex
 ascale? Fortran-based codes present different challenges for performance p
 ortability and productivity. Ideally, we want to develop one codebase that
  can run on many different HPC architectures. In reality, each architectur
 e has its own idiosyncrasies, requiring architecture-specific code. Theref
 ore, we strive to write code that is as portable as possible to minimize t
 he amount of development and maintenance effort. This project investigates
  how different approaches to parallel optimization impact the performance 
 portability for unstructured mesh Fortran codes. In addition, it explores 
 the productivity challenges due to the software tool and compiler support 
 limitations unique to Fortran. For this study, we use the Truchas software
 , a casting manufacturing simulation code, and develop initial ports for O
 penMP CPU, OpenMP offload GPU. and CUDA for computational kernels. There i
 s no CUDA Fortran compiler compatible with Truchas, it must rewrite kernel
  in CUDA C and have the interface linked for C function calls in Fortran. 
 Meanwhile, only the IBM xlf compiler is supported for OpenMP offload GPU a
 t this moment and it is still immature. In additional of the difficulty th
 at Fortran brings, the unstructured mesh uses more complex data access pat
 terns. From the analysis of the Truchas gradient calculation computational
  kernel, we show some success for performance and portability along with s
 ome issues unique to Fortran using unstructured mesh. Through this study, 
 we hope to encourage users and venders to focus on the productive pathways
  to developing Fortran applications for exascale architectures.\n\nTag: Di
 versity, Education, Hot Topics\n\nRegistration Category: Workshop Reg Pass
 \n\nSession Chairs: Toni Collis (Women in High Performance Computing); Wer
 onika Filinger (Edinburgh Parallel Computing Centre (EPCC); University of 
 Edinburgh, Scotland); and Misbah Mubarak (Amazon Web Services)\n\n
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