Astronomical Computer Simulations. Aaron Smith

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1 Astronomical Computer Simulations Aaron Smith 1

2 1. The Purpose and History of Astronomical Computer Simulations 2. Algorithms 3. Systems/Architectures 4. Simulation/Projects 2

3 The Purpose of Astronomical Computer Simulations What are Astronomical Computer Simulations? Astronomical computer simulations are computationally generated representations of astronomical objects (galaxies, clusters, dark matter, etc) used to model subsets of the universe. What purpose do they serve? Simulations are used as experiments to verify cosmological theories. They are created with initial conditions depending on the specific experiment. When run, accurate simulations model their observable counterparts. To what theories can simulations be applied? Expansion of the universe, merging galaxies, star formation, dark matter, etc. 3

4 The Need for Simulations Why Wait? Simulate! Observations could take millions of years. Use the N-body algorithms. In 1941 Erik Holmberg had a bright idea [1] 4

5 The Development of Simulations First computer simulation conducted in 1963 by Sverre Aarseth for ~ n = 100 [2] From there different N-body algorithms developed over time Year 1970 s 1980 s 1990 s 2000 s N 10^3 10^4 10^10 + The N-body problem 5

6 Algorithms 6

7 Particle-Particle (PP) Barnes Hut Tree Direct application of N-body O(n2) No approximation Accuracy = machine precision Most common application of Tree Codes O(nlogn) Octree for 3D Precision and Work dependent on chosen theta 7

8 Particle-Mesh (PM) Particle-Particle/Particle-Mesh(P3M) Apply a mesh over computation area O(GlogG) + O(N) Fix to PM Use PP for small distances Potential fields and Mass density Low resolution 8

9 Other methods Fast multipole method Symplectic integrator layered-ppm Self-Consistent Field 9

10 Systems/Architectures 10

The Modern Landscape RIT s BlueSky Linux -1000 CPUs 4TB memory

computing power -over 4 PetaFLOPS Illustris Project -8,192 CPUs,

11 The Modern Landscape RIT s BlueSky Linux CPUs 4TB memory 200TB storage NASA-AMES -About 250 times BlueSky Linux s computing power -over 4 PetaFLOPS Illustris Project -8,192 CPUs, 25 TB of RAM, 230 TB of gathered data GRAPE -512 PC 2 GRAPE-DR boards each 11

GRAPE-DR Fermi NVIDIA cores 512 448 tranistors 400M 3B

12 GRAPE-DR Hardware acceleration board Works parallel to the cpu Much more efficient when compared to GPGPU GRAPE-DR Fermi NVIDIA cores tranistors 400M 3B clock 400 Mhz 1.15 Ghz flops 400 G 1.03 T power 50 W 247 W 12

13 Simulation/Projects 13

The Millennium Simulation Run by the Virgo Consortium located at the Max Planck Institute for Astrophysics in Garching, Germany. 10 billion particles, each representing 8.

14 The Millennium Simulation Run by the Virgo Consortium located at the Max Planck Institute for Astrophysics in Garching, Germany. 10 billion particles, each representing 8.6 x 10^8 solar masses of dark matter Astronomical Object Dwarf Galaxy Milky Way Galaxy Galaxy Cluster Corresponding Particle Amount ~100 particles ~1,000 particles ~1,000,000+ particles 14

and weak gravitational lensing Large scale, yet relatively precise

15 The Millennium Simulation Spatial resolution of 5 kpc/h Contains over 20 million galaxies Allows for accurate predictions on strong and weak gravitational lensing Large scale, yet relatively precise 28 days of real-time processing Published in Nature in June

Illustris project - On-going group of Astrophysical simulations run by many scientists. - Attempting to get a better understanding of the formation and evolution of galaxies.

16 Illustris project - On-going group of Astrophysical simulations run by many scientists. - Attempting to get a better understanding of the formation and evolution of galaxies. - Includes black holes, dark matter, dark energy - Main simulation - Curie supercomputer at CEA (France) and SuperMUC computer at the Leibniz Computing Center (Germany) - 8,192 CPU cores, 25 TB of RAM, - galaxy matching between FP and DMO runs - non-parametric stellar morphologies at z>0 16

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19 Questions? 19

The Millennium Simulation: cosmic evolution in a supercomputer. Simon White Max Planck Institute for Astrophysics

The Millennium Simulation: cosmic evolution in a supercomputer Simon White Max Planck Institute for Astrophysics The COBE satellite (1989-1993) Two instruments made maps of the whole sky in microwaves