The Gauge Connection is an experimental archive for lattice QCD. It is a repository of gauge configurations made freely available to the community. Contributors to the archive include the Columbia QCDSP collaboration, the MILC collaboration, and others.

Hardware and sysadmin support have been provided by NERSC. The storage and transfer charges are underwritten by the QCD Grand Challenge allocation at NERSC. The archivists and web-masters are Gregory Kilcup and Jim Hetrick, who can collectively be reached at qcd-archive@nersc.gov.

To download configurations, you need to register on-line, giving yourself a userID and password. The intent of this mechanism is to help us keep track of where the data is going, so we can provide a report to our sponsors and contributors. We may also occasionally broadcast Email if the need arises.

Configurations can be downloaded from the server only via http. When accessing the archive from a browser, one can save files as usual with a few mouseclicks. To access the archive without a graphical browser (e.g. inside a script on some supercomputer), we recommend the GNU program wget, which is available from our utilities page. See also wget usage notes.

Configurations are stored in QCD archive format, consisting of an ASCII header which defines various parameters, followed by binary data. We have provided some utilities and examples to help get you started reading the data on your machine.

The one obligation incurred by downloading data is the responsibility to acknowledge the contributing group in any resulting publications. We would also appreciate Email to qcd-archive@nersc.gov calling our attention to such papers when they hit the preprint archive, so that we can add a link to your paper from the appropriate page.

Physically, the archive server is a Sparc-5 sitting on the fast ethernet in the NERSC machine room. When you download a configuration, a script fetches the data from NERSC's HPSS tape robot storage system, stages it on a local disk, and then transmits it back out to you. In the best case, the transfer from HPSS will start almost immediately, and proceed at a rate of about 1 MB/sec. So if, for example, you download a 100 MB file, you should expect at least a 2 minute delay between your mouseclick and the time you get the first bytes back.