2D simulation of the astrophysical n-body problem, optionally distributed using MPI and OpenMP.
Simply make the project and execute the resulting executable nbody.
The input to the simulation is a text file describing the simulated bodies. While the first line gives the total number of bodies, all subsequent lines describe these bodies by specifying their
- inertial mass
- initial position vector
- initial velocity vector
with 5 floating point numbers in total. Example:
2 # two bodies
1.98e30 0 0 0 0 # the sun
5.977e24 1.496e11 0 0 29716 # the earth
To start a simulation, call the compiled executable nbody with
nbody -i input -o output [-t step] [-n n_steps] [-d] [-s] [-p] [-3] [-l] [-W pixels] [-H pixels] [-w width] [-h width] [-A asteps]
where the parameters work as follows:
-i input: Location of the initial body configuration-o output: Where to write the final body configuration-t step: Size of a simulation time step in seconds-n n_steps: Total number of time steps to simulate-p: Execute the simulation in parallel-3: Use Newton's third law for local performance optimization-l: Use Newton's third law for global performance optimization-d: Display helpful debugging output throughout execution-W/-H pixels: Output image width or height, respectively-w width: Width of depicted space in meters-h height: Height of depicted space in meters-A asteps: Steps between two images. If zero, no images will be generated.
The output of the simulation is two-fold:
- The output file specified by
-ohas the same format as the input file given by-ibut contains the location and velocity of the bodies at the end of the simulation. - In addition, every
-A(if not zero) time steps an image file of-W x -Hpixels will be generated depicting the current position of the bodies in a physical area of size-w x -h.
When using this input configuration of two spiral galaxies, simulating 100 steps of 3.16e10 seconds yields this output file. The animated GIF below shows the sequence of images generated in between.
