3 ms·
To put those phrases in context, I think they would have required more effort than the Apollo project. > Obviously, although I have doubts that the computation
by hwillis 5y ago
To put those phrases in context, I think they would have required more effort than the Apollo project.
> Obviously, although I have doubts that the computations being performed by these "GPU solvers" really require a modern custom-built GPU and couldn't have been done on FPGAs or arrays of microcontrollers from the 80s.
Here's a talk by the guys: https://www.youtube.com/watch?v=vYA0f6R5KAI https://www.youtube.com/watch?v=vYA0f6R5KAI
The Cray 2 could do <2 gigaflops. So a single simulation with 10,000 points per side at 1 microsecond timesteps for .1 seconds with ~50 flops per cell-step would have taken 79 years to run, assuming the Cray had 50 cycle fetch/store times. Engineers need to run lots of simulations to come up with a working design. And that's just simulating something around the scale of a single nozzle- you'll need to be doing sims for a 40 meter tall stage as it flips around.
Also, the cray had a 256 Mword memory. So you could only store a single timestep of a grid of 400x400x400 cells anyway. The supercomputers of the 80s were really just not very useful for things like this.
- nexuist 5y agoGoing to watch the video now. Thank you for the explanation! Graphics isn't my primary field so admittedly I don't know what I'm talking about. One thing I love about SpaceX is how engineers are allowed to do talks like this, I barely hear anything from the engineering division at BO or ULA.