2 The Sloan Digital Sky Survey (2000-) is a terapixel visualization of the Universe.

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Austen Goodwin
5 years ago
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2 2 The Sloan Digital Sky Survey (2000-) is a terapixel visualization of the Universe.

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7 7 Individual state of the art cosmological simulations now contain as much information as the SDSS This talk: -How to make images and movies of simulations at full resolution. -How to make them accessible to anyone with a web brower

8 8 Cosmological simulations: start the Universe off with initial conditions from Inflation and then follow known Physics. + Gadget SPH

9 9 we use comoving coordinates

10 10 Number of particles vs year for cosmological simulations Millennium simulation N This talk Moore s law (CPU speed doubles every 18 mo) Rapid rise due to parallelization, better algorithms (From Springel 2005)

11 particles in observable universe if trend continues, reachable by 2300 AD!

12 12 Running simulations: PI Tiziana Di Matteo (CMU) Aim to run on Blue Waters (if it happens ) New code PetaGadget based on smoothed particle hydro/gravity code Gadget by collaboration member Volker Springel

13 Currently largest cosmological hydro simulation published is MassiveBlack which we have carried out using all (10 5 ) cores on Cray XT5 Kraken at NICS: 64 billion particles box size 533

13 13 Currently largest cosmological hydro simulation published is MassiveBlack which we have carried out using all (10 5 ) cores on Cray XT5 Kraken at NICS: 64 billion particles box size 533 Megaparsecs/h kpc resolution Smoothed Particle Hydrodynamics gas cooling and dissipation subresolution modelling of star formation and black hole growth ~0.3 PB data so far Currently also analyzing a run that is twice the size (132 billion particles, 0.7 PB data)

14 14 Computational Challenges and how met: Load balancing : using spacefilling Hilbert curve Dual level parallelism (inter node and inter core) must be exploited: most of code now hybrid MPI/threads Data management Vizualization: this talk Even trivial analysis must be massively parallel: some clustering/groupfinding analysis done on the fly

15 15 Vizualization of the MassiveBlack simulation Goals: a panoramic view of the entire simulation volume containing all details down to the simulation resolution (like SDSS sky image) Difficulties: Volume is cubical not a plane Particle number is enormous- will take long to process Image size would be too big to show on any screen Need to display multiple components (gas, stars, etc)

16 16 SPH vizualization: Particles used to represent a smooth field. SPH kernel W gives extent of each particle Rasterization: particles -> pixels

17 17 Volume is cubical not an image plane: Volume remapping- to show entire volume in one image

18 18 For MassiveBlack, this matrix maps the periodic 533x533x533 cube into a thin slice of dimensions 5844x3288x8 Mpc The simulation resolution is 4 Kpc. An image 5244x3288 Mpc 2 contains resolution elements -> a terapixel image

19 19 Plotting multiple components: Stars, gas, black holes, star formation Alpha compositing:

20 20 Memory requirements are substantial: 1 terapixel x 4 bytes/pixel x 4 fields = 16 TB Image making carried out on SGI Altix Blacklight at Pittsburgh Supercomputing Center (32 TB shared RAM)

21 21 We have a 1 terapixel image how do we view it?!! -at 300 dpi it would cover 2 football (soccer) fields!

22 22 for interactive viewing

23 23 How does GigaPan viewer work? -Image stored as 256x256 pixel tiles at different levels of resolution (14 levels for terapixel image)

24 24 Terapixel image on gigapan.org

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27 27 This is a static image, but Universe evolves in time. If we make multiple images we can use which can display multigigapixel explorable movies.

28 28 in collaboration with CMU s Please go to website to try it out: timemachine.gigapan.org

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30 30 Simulation movie with 1370 x 1 Gigapixel frames. One every 10 million yrs.

31 31 How does GigaPan Time Machine viewer show zoomable movies? -hierarchical storage as with static viewer, but this time using levels of movie tiles at different resolutions -each tile plays on a different viewer, all synced and stitched together seamlessly -uses HTML5 video tag (only works with Chrome, Safari browsers

32 32 Science from MassiveBlack visualization: Cold flows and black hole growth (Di Matteo et al. 2011) Cold gas streams fuel black hole growth to 10 9 M sun at z=6

33 33 Summary: Can visualize any region of a petascale simulation at full resolution, using just a web browser. Thousands of times faster than the old method (reading and sorting through terabytes of particle data) The time domain is now available through GigaPan Time Machine. Please try it out it s fun! All software in this (NSF PetaApps funded) initiative has been released publicly: (see arxiv: )

Swift: task-based hydrodynamics at Durham s IPCC. Bower

Swift: task-based hydrodynamics at Durham s IPCC Gonnet Schaller Chalk movie: Richard Bower (Durham) For the cosmological simulations of the formation of galaxies Bower Institute for Computational Cosmology