GASNet

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GASNet is a language-independent, low-level networking layer that provides network-independent, high-performance communication primitives tailored for implementing parallel global address space SPMD languages such as UPC, Titanium, and Co-Array Fortran. The interface is primarily intended as a compilation target and for use by runtime library writers (as opposed to end users), and the primary goals are high performance, interface portability, and expressiveness. GASNet stands for "Global-Address Space Networking".

The design of GASNet is partitioned into two layers to maximize porting ease without sacrificing performance: the lower level is a narrow but very general interface called the GASNet core API - the design is based heavily on Active Messages, and is implemented directly on top of each individual network architecture. The upper level is a wider and more expressive interface called the GASNet extended API, which provides high-level operations such as remote memory access and various collective operations.


System diagram showing GASNet layers

We've written a network-independent reference implementation of the extended API purely in terms of the core API, which allows GASNet (and the GAS compiler) to quickly and easily be ported to a new network architecture by re-implementing only the minimal core API. GASNet is structured such that implementers can choose to additionally bypass certain functions in the reference implementation of the extended API and implement them directly on the hardware to improve performance of specific operations when hardware support is available (e.g. special network support for puts/gets or hardware-assisted broadcast).

Most clients will use calls to the extended API functions to implement the bulk of their communication work (thereby ensuring optimal performance across platforms). However the client is also permitted to use the core active message interface to implement non-trivial language-specific or compiler-specific communication operations which would not be appropriate in a language-independent API (e.g. implementing distributed language-level locks, distributed garbage collection, collective memory allocation, etc.). The AM features of the core provide a powerful extensibility mechanism which allows clients to implement a wide variety of specialized communication operations. 

GASNet Specification, v1.8:
    Acrobat PDF     Postscript      HTML      Text

For citations, please use:

U.C. Berkeley Tech Report (UCB/CSD-02-1207) (spec v1.1)

Download GASNet Implementation:

GASNet Full Source Release
(all conduits and platforms) 		GASNet-1.10.0.tar.gz   (2 MB)
MD5 Hash = 17eee04a24aa0b00135ea95592ebfac0
Browse the archive
README, Change log, BSD license.
GASNet Portability Tools
(NO communication conduits, GASNet Tools only) 		GASNet_Tools-1.10.0.tar.gz   (400 KB)
MD5 Hash = b9b219369feb67f9230e0d284e14fd4e
README-tools

The full version of GASNet includes support for the following networks:

and has been tested on a number of systems (see README for a complete list):

Work continues on GASNet implementations for other high-performance networks, and code contributions are appreciated (please send email if you're interested). Future releases will add a further-tuned collectives implementation, native support for BlueGene systems, and numerous other improvements to the existing native conduits. Independent implementations of the GASNet specification are also encouraged.

GASNet Performance Results

GASNet Bug Database

Publications/Presentations:

Systems/Projects using GASNet:

Production GASNet clients: Experimental GASNet clients:

Other Related Links:

UPC Language Consortium
Active Messages over MPI (AMMPI)
Active Messages over Ethernet/UDP (AMUDP)
ARMCI Communication System

Contact information:

For more info about GASNet, please contact:
 Dan Bonachea

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Page last updated Thursday November 08, 2007
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