The site's hierarchy

Home page :: Private area :: Site Map :: Credits
Science / Conditions Initiales / Conditions initiales cosmologiques / Codes / GRAFIC I / Description


Mar 2009
  • Les premiers zoom de galaxies sont accessibles
  • Le halo FOF 6133 de la boite Horizon L et le halo FOF 544 de Horizon S ont été resimulés avec plusieurs techniques de zoom. Il est important que chaque "zoomer" valide sa méthode, avant de lancer une campagne de zoom sur un plus grand cataloque.
  • Les données de la simulation Mare Nostrum sont disponibles
  • 34 snapshots jusqu’à z=4 sont accessibles sur horizon3 et sur le serveur de fichiers de l’IDRIS à la collaboration Horizon.
  • Méso Machine HPC1 opérationnelle
  • Depuis le 23 Octobre 2005, la Méso machine du site horizon est operationnelle. Elle correspond à 3 quadriprocesseurs avec chacun 64 Giga de RAM reliés par infiniband, ainsi qu’un access conséquent (sur une base de projet dédié) au reste de la ferme). Son acces est ouvert a toute personne de la collaboration ayant acces à la minigrille et qui en fait la demande a admin-minigrille
  • http://
  • Workshop Horizon le 14 et 15 novembre 2005
  • Il aura lieu à Paris les 14 et 15 novembre 2005 (prévoir une nuit sur place). L’enregistrement est ouvert dans la rubrique "meeting!"
  • http://


by Aubert Dominique (Monday 25 September 2006)


Written by Edmund Bertschinger, GRAFIC I is part of the more extended package GRAFIC and performs the generation of periodic initial conditions for a given cosmology, boxsize, etc... Combined with GRAFIC 2, zoomed-in initial conditions may be generated from this code.

Articles & Documentation

-  ’Multiscale Gaussian Random Fields and Their Application to Cosmological Simulations’, ApJ,2001, 137,1-20
- Code Documentation

texte - 16.3 kb

Versions and Where to find it ?

Grafic 1 can be easily hacked to fit the requirements of a simulation code. Two versions are given here:
- The original version. It can be requested directly from E. Bertschinger ( or from

GZ - 257.8 kb
Original version of grafic


Straightforward via a Makefile. Does not require any specific librairy.


- Written in f77.
- Serial code.



Most of the inputs consists in defining the transfer function. The transfert function may be provided by the code ’linger’ (included in the Grafic archive) or be computed by the Grafic 1 code itself via a fitting formula. In the latter case, the user gives interactively the cosmological parameters, the boxsize, the normalisation, etc... Originally the code only provides the BBKS transfert function and assumes omegab=0. Other TFs are included in the ’power.f’ file but should be commented out by hand.

A few parameters should be ’hard coded’ in the ’’ file:
- the number of grid cells (np1,np2,np3)
- the amplitude of white noise fluctuations
- the offset in positions between baryons and DM particles. Some codes crash if particles are too close and require such an offset. Any change in these parameters requires a re-compilation.


GRAFIC 1 outputs seven files : the density field (1 file, ic_deltab), the velocity field for the baryons (3 files, ic_velbx/y/z) and the velocity field for the dark matter (3 files, ic_velcx/y/z). The code can also outputs the white-noise file. This file may be given to the code as an input in order to study different cosmologies or different boxsize with the same overall structure in the simulation.

IMPORTANT: if the BBKS transfert function is used, the velocity fields of baryons and DM are identical. In order to gain computation time or disk space, the user may want to hack the code to produce only the first four fields.