Il sistema di calcolo ad alte prestazioni del CINECA: evoluzione di ...

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MPI vs. OpenMP Pure MPI Pro: High scalability High portability No false sharing Scalability within the node Pure MPI Cons: Not easy to develop and debug Explicit communication Big granularity Not easy to garantee a good Load balancing Pure OpenMP Pro: Easy to implement (in general) Low latency Implicit Communication Coarse and fine granularity Load balancing dynamic Pure OpenMP Cons: Only on shared memory architectures Scalability only within the node Wait for the unlock of data Not specifoc order for threads Cache consistency and false sharing www.cineca.it 16
MPI plus OpenMP Pro: Better use of memory hierarchy Better use of interconnection Use of OpenMP within a node avoids overheads associated with calling the MPI library Improve scalability Cons: Overhead in thread management Greater attention to memory access Worse performances (in some cases) www.cineca.it 17
Page 1 and 2: CINECA Casalecchio di Reno (BO) www
Page 3 and 4: Parallel Architectures P P M P P SM
Page 5 and 6: Process A process is created by the
Page 7 and 8: MPI Execution Model - Single Progra
Page 9 and 10: Processors: trends Aggregate Number
Page 11 and 12: Hybrid Model Multi-node SMP (Symmet
Page 13 and 14: www.cineca.it 13
Page 15: Domain decomposition /1 The hybrid
Page 19 and 20: Hybrid pseudo code call MPI_INIT (i
Page 21 and 22: Mixed paradigm www.cineca.it 21
Page 23 and 24: MPI_THREAD_SINGLE (master only) !$O
Page 25 and 26: MPI_THREAD_FUNNELED - calls outside
Page 27 and 28: MPI_THREAD_SERIALIZED • Outside t
Page 29 and 30: HPC Evolution From Herb Sutter Moor
Page 31 and 32: Real HPC Crisis is with Software A
Page 33: Some Current Unmet Needs Performanc

Il sistema di calcolo ad alte prestazioni del CINECA: evoluzione di ...

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