Cosmic Microwave Background Data Analysis At NERSC Julian Borrill with Christopher Cantalupo Theodore Kisner

What Is The CMB ? A snapshot of the Universe when it first became neutral 400,000 years after the Big Bang. Cosmic - filling all of space. Microwave - redshifted by the expansion of the Universe from 3000K to 3K. Background - primordial photons coming from “behind” all astrophysical sources.

Why Do We Care About The CMB ? The CMB is a unique probe of the very early Universe. Its tiny (1: ) fluctuations carry information about - the fundamental parameters of cosmology - ultra-high energy physics beyond the Standard Model

What Does The CMB Look Like ?

CMB Work At NERSC Started in 1997: –2 separate allocations for Maxima & Boomerang –together 5 users & 30,000 CPU-hours Developed into premier world center for CMB analysis: –single allocation shared by O(10) experiments –O(100) users & O(1,000,000) MPP-hrs/year Now includes "Big Science" satellite mission –split into two allocations mp sub-orbital experiments 40 users & 500,000 MPP-hrs planck: Planck satellite 60 users & 2,000,000 MPP-hrs*

The Planck Satellite The primary driver for current NERSC CMB work. A joint ESA/NASA mission due to launch in the fall of An 18+ month all-sky survey at 9 microwave frequencies from 30 to 857 GHz. O(10 12 ) observations, O(10 8 ) sky pixels, O(10 4 ) spectral multipoles.

Data Management Dominated by time-ordered data –O(1-10) TB, O(10, ,000) files Each data set must be analyzed as a whole. Each data analysis needs O(100x) storage. Each data set may have its own format/distribution. Each data set must be selectively shared. Requires –Pre-fetching & active disk quota management –Efficient & abstracted run-time reading –Project account

Task Management Any member of a team must be able to –Access all the data –Access all the general & project-specific codes –Generate and execute standard analyses –Share the results with the team Some members of a team must be able to –Control the overall team work-load/-distribution –Manage software versioning and access Requires –Project account with individual user certification –Limited capability for most; full capability for some. –Synchronized data-for-task management

A Framework for CMB Analysis At NERSC Data Management Data staging Run-time IO Memory Task Management User Project

Critical Components & Issues NERSC Global Filesystem –access from Franklin Storage Resource Manager –optimal transfer protocols Project quotas –separation from UNIX groups Project accounts –appropriate queue limits User accounts –maintain (unique) accessibility Modules –work just fine

Conclusions NERSC has developed into the world's leading center for HPC for CMB data analysis –Recognized as such by the recent NASA/NSF/DOE Weiss report on the future of CMB research. This reflects the NERSC resources' –capacity and capability, –accessibility, –long-range development plan. Long may it continue !