Writing N-body gravity simulations code in Python
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Writing N-body gravity simulations code in Python
1–10 of 51 posts
Re: Writing N-body gravity simulations code in Python
#2Very well done!
Re: Writing N-body gravity simulations code in Python
#3Once you have the matrix implementation in Step 2 (Implementation 3) it's rather straightforward to extend your N-body simulator to run on a GPU with Jax --- you can just add `import jax.numpy as jnp` and replace all the `np.`s with `jnp`s.
For a few-body system (e.g., the Solar System) this probably won't provide any speedup. But once you get to ~100 bodies you should start to see substantial speedups by running the simulator on a GPU.
Re: Writing N-body gravity simulations code in Python
#4Every time I see anything on the N-Body problem I am reminded by my final high school project... I had 2-3 weeks of time to write an n-body simulation. Back then I used C++ and my hardware was really bad (2 GHz single core CPU or so…). The result was not really impressive because it did not really work. :D But I was able to show that my code correctly predicted that the moon and the earth would eventually collide without any initial velocity given to both bodies. I went into this totally naive and blind but it was a ton of fun.
Re: Writing N-body gravity simulations code in Python
#5In Step 2 (Gravity), why are we summing over the cube of the distance between the bodies in the denominator?
Edit: To answer myself, I think this is because one of the factors is to normalize the vector between the two bodies to length 1, and the other two factors are the standard inverse square relationship.
Re: Writing N-body gravity simulations code in Python
#6[deleted]
Re: Writing N-body gravity simulations code in Python
#7Once you have the matrix implementation in Step 2 (Implementation 3) it's rather straightforward to extend your N-body simulator to run on a GPU with Jax --- you can just add `import jax.numpy as jnp` and replace all the `np.`s with `jnp`s. For a few-body system (e.g., the Solar System) this probably won't provide any speedup. But once you get to ~100 bodies you should start to see substantial speedups by running the…
> rather straightforward
For the programmer, yes it is easy enough.
But there is a lot of complexity hidden behind that change. If you care about how your tools work that might be a problem (I'm not judging).
Re: Writing N-body gravity simulations code in Python
#8Man I tried doing this once and my brain nearly melted lol props for actually making it work
Re: Writing N-body gravity simulations code in Python
#9Every time I see anything on the N-Body problem I am reminded by my final high school project... I had 2-3 weeks of time to write an n-body simulation. Back then I used C++ and my hardware was really bad (2 GHz single core CPU or so…). The result was not really impressive because it did not really work. :D But I was able to show that my code correctly predicted that the moon and the earth would eventually collide wit…
> my hardware was really bad (2 GHz single core CPU or so…)
laughs in 32kb of RAM
Sounds like a great project, though. There's a lot of fundamental concepts involved in something like this, so it's a great learning exercise (and fun as well!) :)
Re: Writing N-body gravity simulations code in Python
#10My favorite thing about this kind of code is that people are constantly inventing new techniques to do time integration. It's the sort of thing you'd think was a solved problem but then when you read about time integration strategies you realize how rich the space of solutions are. And they are more like engineering problems than pure math, with tradeoffs and better fits based on the kind of system.