Lawrence Berkeley National Laboratory

Power Play

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“If there’s a difficult project that NERSC staff can work with the scientific users on, it often turns into a scientific collaboration,” with the staff member listed as a joint author on research, Simon adds.

Pratt, who scaled his mathematical models up from the single processor in his desktop computers to eight processors, says NERSC experts were helpful.  Without access to high-performance computing, “There are projects I would not have been able to complete,” he says.  “We were able to find out a lot about the chemistry through computational mechanisms that would not have been easily obtained by experiment.”

A series of “snapshots” of the carbon mass fraction for a thermonuclear flame. Click image for larger version and more information

Large allocations of NERSC computer time generally are awarded competitively through annual requests for proposals, with DOE program managers making the decisions.  Computing experts at NERSC, Argonne National Laboratory, Oak Ridge National Laboratory, and Pacific Northwest National Laboratory judge whether the codes and algorithms described in the proposals are ready to run on massively parallel machines.  Peer review panels scrutinize the proposals for their impact on science.  “This is sort of self-selecting, because the people who apply know what the reviewers are looking for,” Simon says.

In the past, requests often totaled more than 10 times the amount of available time.  Now the deployment of ever-more-powerful computers allows NERSC to meet about half of the requests.  While NERSC seeks to accommodate projects and investigators with little or no background in parallel processing or high-end computing, those are becoming rare as parallel machines become ubiquitous.

The process and facilities may seem daunting, but it’s not hard to get a foot in the door.  New users who want to try their codes or develop new ones on NERSC machines can apply online for a startup allocation. Startups must meet the Office of Science mission and require high-performance computing.

NERSC is making it even easier for DOE CSGF fellows.  It’s allocating 40,000 to 50,000 startup hours to between 50 and 70 projects fellows put forward.  The allocations will let students see how well their codes scale in parallel, and enable them to work with NERSC consultants to improve their projects and code performance.

The idea is to get fellows to look beyond the computational resources they have at hand through their major professor or department, says David Skinner, leader of NERSC’s Open Software and Programming Group and coordinator for the SciDAC Outreach Center (see sidebar).  Some students may have discovered NERSC Center computer resources if their advisor has used them, but the goal is to attract even those who have not worked with the center before.

Fellows can go to a Web page and fill out a survey about their computing needs.  About half of respondents through summer 2007 “were people who said ‘This is where I’m generally headed, but I’m not there yet,’ ” Skinner says, but other fellows said they can’t get their research done fast enough with their present computer resources.

“A couple…said ‘My workstation is too slow for the work,’ ” Skinner says. “For those, my response was to get them onto some high-performance computing facilities,” either at NERSC or another national laboratory, such as Oak Ridge or Argonne.  The startup allocations should let fellows try out their codes for up to 18 months.

Students, Simon says, often are shy about asking for help getting their codes to run on NERSC Center computers.  Many are accustomed to solving their own computer problems and working with university computing centers that often were staffed by their fellow students, Simon adds.  They’re “quite surprised when they come to NERSC, because we are a full-service organization.”

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