PHYSICS 141/241

Winter 2006

Laboratory Session IV

2/6/06

1. Leapfrog Integration

Short overview of the leapfrog method  

Leapfrog_labnote.pdf 

Leapfrog_labnote.ppt 
2. Fortarn and C Practice with the Aarseth Code

  • nbody0.tar.gz (Fortran code)

  • There are instruction below how to run the Fortran code.

  • nbody0-lab.c  C code 

  • initc.data

  • Running the C code:
  • Compilation of C code: gcc -o xnbody nbody0-lab.c -lm
  • To run: xnbody reads in initc.data file and ouputs sphere.data. 
  • initc.data  has 1 header line plus one line for each particle in 7 columns: mass, x, y, z, vx, vy, vz
  • header line of initc.data has 5 data: # of particles, eta=0.02, dt, tmax, epsilon**2=0.25
  • sphere.data has 4 columns: mass, x, y, z


    •
  • Running the Fortran code:

  • Save, gunzip and untar in a directory:

    gunzip nbody0.tar.gz

    tar tvf nbody0.tar

    tar xvf nbody0.tar

    equivalently:

    gunzip -d -c nbody.tar.gz | tar xvf -

  • Compile the Fortran code:

    g77 -o xrun main.f nbody0.f nbodyio.f

  • Generate initial star distribution with 3000 points

  • Run the test program first

    xnb0 < data.in &

  • Visualize and animate with DX