Millennium Database Overview and some first usage experiences Gerard Lemson and the Virgo Consortium astro-ph/0608019 2007 -05 -15 TIG session 3+Millennium database
The Virgo consortium’s Millennium simulation • Millennium simulation – – – 10 billion particles, dark matter only 500 Mpc (~2 Gly) periodic box “concordance model” (as of 2004) initial conditions 64 snapshots 350000 CPU hours O(30 Tb) raw + post-processed data • Postprocessing: – dark matter density fields smoothed at various scales (45 * 2563 grid cells) – dark matter cluster merger trees (~750 million) – galaxy merger trees (~1 billion/catalogue) • De. Lucia & Blaizot, 2006 • Bower et al, 2006 2007 -05 -15 TIG session 3+Millennium database
Dark matter and galaxies 2007 -05 -15 TIG session 3+Millennium database
Halos and galaxies 2007 -05 -15 TIG session 3+Millennium database
Database design 2007 -05 -15 TIG session 3+Millennium database
Database design: “ 20 queries” 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Return the galaxies residing in halos of mass between 10^13 and 10^14 solar masses. Return the galaxy content at z=3 of the progenitors of a halo identified at z=0 Return the complete halo merger tree for a halo identified at z=0 Find properties of all galaxies in haloes of mass 10**14 at redshift 1 which have had a major merger (mass-ratio < 4: 1) since redshift 1. 5. Find all the z=3 progenitors of z=0 red ellipticals (i. e. B-V>0. 8 B/T > 0. 5) Find the descendents at z=1 of all LBG's (i. e. galaxies with SFR>10 Msun/yr) at z=3 Find all z=3 galaxies which have NO z=0 descendent. Return all the galaxies within a sphere of radius 3 Mpc around a particular halo Find all the z=2 galaxies which were within 1 Mpc of a LBG (i. e. SFR>10 Msun/yr) at some previous redshift. Find the multiplicity function of halos depending on their environment (overdensity of density field smoothed on certain scale) Find the dependency of halo formation times on environment 2007 -05 -15 TIG session 3+Millennium database
Time evolution: merger trees 2007 -05 -15 TIG session 3+Millennium database
Merger trees : select prog. from galaxies des , galaxies prog where des. galaxy. Id = 0 and prog. galaxy. Id between des. galaxy. Id and des. last. Progenitor. Id Leaves : select galaxy. Id as leaf from galaxies des where galaxy. Id = last. Progenitor. Id Branching points : select descendant. Id from galaxies des where descendant. Id != -1 group by descendant. Id having count(*) > 1 2007 -05 -15 TIG session 3+Millennium database
More database design features • Spatial indices – Peano-Hilbert index links to field (256^3) – Z-curve index (bit interleaved, 256^3) • SQLServer 2005 CLR integration with C# for range queries – Zone index (ix/iy/iz, 50^3) select from where and * galaxies snapnum = 63 ix = 1 and iy = 5 and iz = 20 • Random sampling select from where and 2007 -05 -15 * galaxies snapnum = 63 random between 1000 and 2000 TIG session 3+Millennium database
the Millennium database web server • Web application (Java in Apache tomcat web server) – portal: http: //www. mpa-garching. mpg. de/millennium/ – public DB access: http: //www. g-vo. org/Millennium • 30 sec/1000 rows | 30 sec/unlimited rows – private access: http: //www. g-vo. org/My. Millennium • 30 sec/1000 rows | 420 sec/unlimited rows – My. DB, 1 Gb, sometimes more • Access methods – browser with plotting capabilities through VOPlot applet – wget + IDL, R – TOPCAT plugin 2007 -05 -15 TIG session 3+Millennium database
2007 -05 -15 TIG session 3+Millennium database
2007 -05 -15 TIG session 3+Millennium database
2007 -05 -15 TIG session 3+Millennium database
Usage statistics • Up since Aug 2006 • Community notified via preprint server http: //xxx. lanl. gov/abs/astro-ph/0608019 • Obtained form DB-base log with SQL • > 130 registered users • almost 1. 7 million queries (not all correct) • since March 3, >5 billion rows handled 2007 -05 -15 TIG session 3+Millennium database
2007 -05 -15 TIG session 3+Millennium database
Usage patterns • • • Start with milli-Millennium (1/512 of full) Some download complete set Mainly to test approach, SQL Ask for account on full Millennium Run into timeout – either ask me – cut query in pieces – execute via script, using wget (good for hit rate count of site!) • My. DB usage – small projects collaborate via results, – upload own data (when local at MPA, or via me) 2007 -05 -15 TIG session 3+Millennium database
Conclusions • If you have valuable data (and “if you build it”), “they will come” • PR helps – astro-ph/ – presentations by owners (Simon White, Volker Springel, Carlos Frenk) • Users are not stupid – can and will learn SQL – don’t mind learning SQL (especially when relatively young) – come up with interesting solutions on their own • Documentation important – not optimal yet: indexes, internal relationships • Help desk (i. e. me) helps and is much appreciated • Possible/planned improvements – full upload facility into My. DB – mirror machine with CAS jobs • longer timeouts • batch querying • collaboration easier 2007 -05 -15 TIG session 3+Millennium database
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