Open-Source Astrophysics with the Enzo Community Code Brian W. O Shea Michigan State University
What is Enzo? N-body + hydro (+MHD + RHD +...) blockstructured AMR code originally written at NCSA (by Greg Bryan & Mike Norman) Publicly available: http://enzo-project.org One of the PRAC codes for Blue Waters (two separate projects: O Shea et al., Nagamine et al.)
What science does Enzo enable? cosmology (large scale structure, dark energy, galaxy clusters) galaxy formation (both in cosmological context and isolated) star formation (Pop III/high redshift, modern-day) accretion disks turbulence (HD, MHD, self-gravitating) instabilities in compressible fluids probably more
History
1996-2003: closed-source!
March 2004: Enzo 1.0
November 2008: Enzo 1.5
June 2010: Enzo 2.0
June 2010: Enzo 2.0
June 2010: Enzo 2.0
June 2010: Enzo 2.0
October June 2010: 2011: Enzo Enzo 2.02.1
The Enzo community today 25 contributors (~12 active developers) at >10 institutions ~200 people on enzo-users mailing list (~50% active?) ~80 million SUs devoted to Enzo simulations in 2011 from NSF, NASA, DOE (with more in 2012) Financial support from NSF (AST, OCI, PHY), NASA, and DOE Complementary community: yt (http://ytproject.org): see tomorrow s talk by Matt Turk!
Development model Entirely distributed development model: small number of devs per institution! Code distribution using mercurial (BitBucket) Use code forks / pull requests to move features from development branches into main branch of the code Almost all development discussion takes place on archived, public mailing list and on Google DOcs (meeting notes emailed out)
Community support Most developers are astrophysicists scratching their own itch (and funded to do science!) Development spurred by ~1.5 workshops/year + periodic task-oriented code sprints Active mailing lists for users and developers Development funded by many streams: universities, federal agencies, postdoctoral fellowships Complementary yt development has helped to spur usage of Enzo!
Impact Enthusiastic and heavily-involved user/developer community Enzo is widely known in astrophysics - strongly represented in code comparisons, conference talks/posters - and highly trusted Code is flexible and extensible: high science/ dollar! Has spurred development of open-source science Involvement in this community has strongly affected young scientists career trajectories
Challenges No Fearless Leader of development process: hard to make major code revisions (esp. user-facing) Part-time developers: distractions, hard to do boring but important infrastructure projects Significant work required to build consensus and keep community together!
Recent Enzoenabled results
Radio emission from cosmic ray electrons in galaxy clusters Skillman, Hallman, O Shea, Burns, Smith & Turk 2011, Astrophysical Journal, 735, 96 and Skillman, et al. 2012, ApJ, submitted
Evolution of the intergalactic medium Smith, Hallman, Shull & O Shea 2011, Astrophysical Journal, 731, 6
Phase Flux
Self-gravitating star forming clouds Collins et al. 2012, ApJ, 750, 13
Reionization of the Universe So, Norman, Harkness, Reynolds 2012 (in prep.)
Conclusions Conversion of a code from closed-source to an open-source community code is not without technical and sociological challenges.
Conclusions For the Enzo collaboration, this transition has been worth it: Enhanced transparency/reproducibility (more trust in the code) Larger user base: more eyes on the code, wider adoption More and better science per dollar!
Conclusions The benefits can be seen in the wide variety of science produced by Enzo users! cosmology galaxy formation star formation accretion disks turbulence fluid instabilities and more!
Questions?
Acknowledgments Collaborators: Michael Norman (UCSD/SDSC), Matthew Turk (Columbia), Jack Burns (CU/Boulder), Eric Hallman (CfA/Tech-X), Robert Harkness (SDSC), Dan Reynolds (SMU), Sam Skillman (CU/ Boulder), Britton Smith (MSU), Geoffrey So (UCSD), Rick Wagner (UCSD/SDSC), John Wise (GATech) The Enzo development consortium Funding through NSF (AST, OCI, PHY), NASA, DOE Computational time through NSF (Teragrid/XSEDE), NASA, DOE