NAS FT Variants Performance Summary Best MFlop rates for all NAS FT Benchmark versions 1100 .5 Tflops Best NAS Fortran/MPI 1000 Best NAS Fortran/MPI Best MPI (always Slabs) 1000 Best MPI Best UPC (always Pencils) 900 Best UPC 800 800 • Slab is always best for MPI; small message cost too high MFlops per Thread MFlops per Thread 700 • Pencil is always best for UPC; more overlap 600 600 500 400 400 300 200 200 100 0 Myrinet 64 InfiniBand 256 Elan3 256 Elan3 512 Elan4 256 Elan4 512 0 Myrinet 64 InfiniBand 256 Elan3 256 Elan3 512 Elan4 256 Elan4 512 4/1/16 � CS267 Lecture: UPC � 61 � Joint work with Chris Bell, Rajesh Nishtala, Dan Bonachea �
FFT Performance on BlueGene/P PGAS implementations HPC Challenge Peak as of July 09 is • consistently outperform MPI ~4.5 Tflops on 128k Cores Leveraging communication/ • 3500 computation overlap yields best performance Slabs 3000 Slabs (Collective) More collectives in flight • Packed Slabs (Collective) and more communication 2500 MPI Packed Slabs leads to better performance GFlops 2000 At 32k cores, overlap • algorithms yield 17% 1500 improvement in overall G 1000 application time O Numbers are getting close to • O 500 HPC record D Future work to try to beat • 0 the record 256 512 1024 2048 4096 8192 16384 32768 Num. of Cores 62
Case Study: LU Factorization • Direct methods have complicated dependencies - Especially with pivoting (unpredictable communication) - Especially for sparse matrices (dependence graph with holes) • LU Factorization in UPC - Use overlap ideas and multithreading to mask latency - Multithreaded: UPC threads + user threads + threaded BLAS • Panel factorization: Including pivoting • Update to a block of U • Trailing submatrix updates • Status: - Dense LU done: HPL-compliant - Sparse version underway 4/1/16 � CS267 Lecture: UPC � 63 � Joint work with Parry Husbands �
UPC HPL Performance X1 Linpack Performance Opteron Cluster Altix Linpack Linpack Performance • MPI HPL numbers Performance 1400 from HPCC MPI/HPL 160 1200 UPC database 140 200 1000 120 • Large scaling: 100 800 150 GFlop/s • 2.2 TFlops on 512p, GFlop/s GFlop/s 80 600 • 4.4 TFlops on 1024p 100 MPI/HPL 60 MPI/HPL 400 (Thunder) UPC 40 UPC 50 200 20 0 0 0 Alt/32 60 X1/64 X1/128 Opt/64 • Comparison to ScaLAPACK on an Altix, a 2 x 4 process grid - ScaLAPACK (block size 64) 25.25 GFlop/s (tried several block sizes) - UPC LU (block size 256) - 33.60 GFlop/s, (block size 64) - 26.47 GFlop/s • n = 32000 on a 4x4 process grid - ScaLAPACK - 43.34 GFlop/s (block size = 64) - UPC - 70.26 Gflop/s (block size = 200) 4/1/16 � CS267 Lecture: UPC � 64 � Joint work with Parry Husbands �
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