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Introduction to Hybrid Parallel Programming – Combining MPI, OpenMP and the Stommel Model

Introduction to Hybrid Parallel Programming – Combining MPI, OpenMP and the Stommel Model. Combine MPI and OpenMP. Hybrid parallel programming approach – each MPI process spawns n OpenMP threads

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Introduction to Hybrid Parallel Programming – Combining MPI, OpenMP and the Stommel Model

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  1. Introduction to Hybrid Parallel Programming – Combining MPI, OpenMP and the Stommel Model

  2. Combine MPI and OpenMP Hybrid parallel programming approach – each MPI process spawns n OpenMP threads • One programming methodology for hybrid architectures, such as coupled shared-memory nodes - e.g., IBM Blue Horizon • Works well on the IBM SP – 8 cpus/node • Run two MPI processes per node • Each MPI process runs 4 MPI threads • We simply combine our Stommel model version stf_002.f (MPI) with the OpenMP enabled subroutine do_jacobi

  3. Combine MPI and OpenMP Hybrid parallel programming approach – each MPI process spawns n OpenMP threads • One programming methodology for hybrid architectures, such as coupled shared-memory nodes - e.g., IBM Blue Horizon • Works well on the IBM SP – 8 cpus/node • Run two MPI processes per node • Each MPI process runs 4 MPI threads • We simply combine our Stommel model version stf_002.f (MPI) with the OpenMP enabled subroutine do_jacobi

  4. IBM SP Running OpenMP & MPI mpxlf_r -qfree=f90 -O3 -qtune=pwr3 -qarch=pwr3 -qsmp omp_02.f -o omp_02 cat run_both #! /usr/bin/ksh -f printenv | grep MP_ export OMP_NUM_THREADS=4 omp_02 < st.in We have MPI and OpenMP Script file to set 4 threads and run job This script is run from LoadLeveler

  5. New IBM SP running OpenMP & MPI #! /usr/bin/ksh #@ environment = COPY_ALL; MP_EUILIB = us #@initialdir = /nhome/your-username #@ output = $(jobid).out #@ error = $(jobid).out #@ job_type = parallel #@ class = high #@ network.MPI = css0,not_shared,US #@ node_usage = not_shared #@ node = 2 #@ tasks_per_node = 2 #@ wall_clock_limit = 1:00:00 #@ notify_user = tkaiser@sdsc.edu #@ notification = error #@ notification = complete #@ queue poe run_both Don’t share the nodes Run on 2 nodes with 2 MPI tasks/node Script file to set threads and run job cat run_both #! /usr/bin/ksh -f printenv | grep MP_ export OMP_NUM_THREADS=4 omp_02 < st.in

  6. Hybrid Programming – MPI & OpenMP • Could also combine MPI and Pthreads • Hybrid method – should study algorithm before coding to justify extra work • Some cases have shown theoretical benefits of hybrid method • Some cases have shown practical advantages of hybrid method

  7. Summary • We can combine OpenMP with MPI to take advantage of hybrid machines

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