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Cited by 3 publications
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GASNet-EX: A High-Performance, Portable Communication Library for Exascale
Partitioned Global Address Space (PGAS) models, typified by languages such as Unified Parallel C (UPC) and Co-Array Fortran, expose one-sided communication as a key building block for High Performance Computing (HPC) applications. Architectural trends in supercomputing make such programming models increasingly attractive, and newer, more sophisticated models such as UPC++, Legion and Chapel that rely upon similar communication paradigms are gaining popularity.GASNet-EX is a portable, open-source, high-performance communication library designed to efficiently support the networking requirements of PGAS runtime systems and other alternative models in future exascale machines. The library is an evolution of the popular GASNet communication system, building upon over 15 years of lessons learned. We describe and evaluate several features and enhancements that have been introduced to address the needs of modern client systems. Microbenchmark results demonstrate the RMA performance of GASNet-EX is competitive with several MPI-3 implementations on current HPC systems. -EX: A High-Performance Communication Library for Exascale PGAS system such as global pointer representation and allocation strategy to the client), robust multithreading support (efficiently allowing a variety of client threading models on multi-core architectures), and widespread portability. The GASNet development effort has focused on providing a high-performance, production-quality communication layer tailored for the needs of PGAS systems. The GASNet API [17] has become the de-facto communication standard targeted by portable PGAS system implementations developed by many institutions. Current and historical GASNet clients include: LBNL UPC++ [3, 4, 79], Berkeley UPC [22], GCC/UPC [46], Clang UPC [45], Cray Chapel [19], Stanford Legion [6], Titanium [78], Rice Co-Array Fortran [26], OpenUH Co-Array Fortran [29], OpenCoarrays in GCC Fortran [32], OpenSHMEM Reference implementation [70], Omni XcalableMP [57], and several miscellaneous projects [10,18,20,27,51,52,71]. Some of these clients implement models that fall outside the traditional PGAS definition, showing that the applicability of GASNet exceeds the original goals. The services provided and the match to modern hardware capabilities make GASNet an excellent communication substrate for implementing a wide variety of models.GASNet uses the term "conduit" to refer to any complete implementation of the GASNet API which targets a specific network device or lower-level networking layer. GASNet conduits have been written that target a variety of past and current vendor-proprietary or hardware-specific networking interfaces, including: OpenFabrics Verbs/VAPI for InfiniBand [37,42], Mellanox MXM for InfiniBand [53], Cray GNI for Gemini and Aries fabrics [1, 36, 41], Intel PSM2 for Omni-Path [9, 44], IBM PAMI for BlueGene/Q (and others) [49], IBM DCMF for BlueGene/P [50, 63], IBM LAPI for SP Colony/Federation [40], Cray Portals for XT3/XT4 [16], SHMEM for the Cray X1 [8] and SGI Altix [28], Quadrics elan3/e...
GASNet-EX: A High-Performance, Portable Communication Library for Exascale
Partitioned Global Address Space (PGAS) models, typified by languages such as Unified Parallel C (UPC) and Co-Array Fortran, expose one-sided communication as a key building block for High Performance Computing (HPC) applications. Architectural trends in supercomputing make such programming models increasingly attractive, and newer, more sophisticated models such as UPC++, Legion and Chapel that rely upon similar communication paradigms are gaining popularity.GASNet-EX is a portable, open-source, high-performance communication library designed to efficiently support the networking requirements of PGAS runtime systems and other alternative models in future exascale machines. The library is an evolution of the popular GASNet communication system, building upon over 15 years of lessons learned. We describe and evaluate several features and enhancements that have been introduced to address the needs of modern client systems. Microbenchmark results demonstrate the RMA performance of GASNet-EX is competitive with several MPI-3 implementations on current HPC systems. -EX: A High-Performance Communication Library for Exascale PGAS system such as global pointer representation and allocation strategy to the client), robust multithreading support (efficiently allowing a variety of client threading models on multi-core architectures), and widespread portability. The GASNet development effort has focused on providing a high-performance, production-quality communication layer tailored for the needs of PGAS systems. The GASNet API [17] has become the de-facto communication standard targeted by portable PGAS system implementations developed by many institutions. Current and historical GASNet clients include: LBNL UPC++ [3, 4, 79], Berkeley UPC [22], GCC/UPC [46], Clang UPC [45], Cray Chapel [19], Stanford Legion [6], Titanium [78], Rice Co-Array Fortran [26], OpenUH Co-Array Fortran [29], OpenCoarrays in GCC Fortran [32], OpenSHMEM Reference implementation [70], Omni XcalableMP [57], and several miscellaneous projects [10,18,20,27,51,52,71]. Some of these clients implement models that fall outside the traditional PGAS definition, showing that the applicability of GASNet exceeds the original goals. The services provided and the match to modern hardware capabilities make GASNet an excellent communication substrate for implementing a wide variety of models.GASNet uses the term "conduit" to refer to any complete implementation of the GASNet API which targets a specific network device or lower-level networking layer. GASNet conduits have been written that target a variety of past and current vendor-proprietary or hardware-specific networking interfaces, including: OpenFabrics Verbs/VAPI for InfiniBand [37,42], Mellanox MXM for InfiniBand [53], Cray GNI for Gemini and Aries fabrics [1, 36, 41], Intel PSM2 for Omni-Path [9, 44], IBM PAMI for BlueGene/Q (and others) [49], IBM DCMF for BlueGene/P [50, 63], IBM LAPI for SP Colony/Federation [40], Cray Portals for XT3/XT4 [16], SHMEM for the Cray X1 [8] and SGI Altix [28], Quadrics elan3/e...
UPC++: A High-Performance Communication Framework for Asynchronous Computation
UPC++ is a C++ library that supports highperformance computation via an asynchronous communication framework. This paper describes a new incarnation that differs substantially from its predecessor, and we discuss the reasons for our design decisions. We present new design features, including future-based asynchrony management, distributed objects, and generalized Remote Procedure Call (RPC).We show microbenchmark performance results demonstrating that one-sided Remote Memory Access (RMA) in UPC++ is competitive with MPI-3 RMA; on a Cray XC40 UPC++ delivers up to a 25% improvement in the latency of blocking RMA put, and up to a 33% bandwidth improvement in an RMA throughput test. We showcase the benefits of UPC++ with irregular applications through a pair of application motifs, a distributed hash table and a sparse solver component. Our distributed hash table in UPC++ delivers near-linear weak scaling up to 34816 cores of a Cray XC40. Our UPC++ implementation of the sparse solver component shows robust strong scaling up to 2048 cores, where it outperforms variants communicating using MPI by up to 3.1x.UPC++ encourages the use of aggressive asynchrony in lowoverhead RMA and RPC, improving programmer productivity and delivering high performance in irregular applications.
UPC++ is a C++ library implementing the Asynchronous Partitioned Global Address Space (APGAS) model. We propose an enhancement to the completion mechanisms of UPC++ used to synchronize communication operations that is designed to reduce overhead for on-node operations. Our enhancement permits eager delivery of completion notification in cases where the data transfer semantics of an operation happen to complete synchronously, for example due to the use of shared-memory bypass. This semantic relaxation allows removing significant overhead from the critical path of the implementation in such cases. We evaluate our results on three different representative systems using a combination of microbenchmarks and five variations of the the HPCChallenge RandomAccess benchmark implemented in UPC++ and run on a single node to accentuate the impact of locality. We find that in RMA versions of the benchmark written in a straightforward manner (without manually optimizing for locality), the new eager notification mode can provide up to a 25% speedup when synchronizing with promises and up to a 13.5x speedup when synchronizing with conjoined futures. We also evaluate our results using a graph matching application written with UPC++ RMA communication, where we measure overall speedups of as much as 11% in single-node runs of the unmodified application code, due to our transparent enhancements.
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