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> The theoretical maximum rate for 1B particle advection (Just doing p[] += v[]ddt), is 1000GB/s / 24GB =41.667/s 42 iteration per second. Just to clarify, the 24GB comes from multiplying 1B particles by 24 bytes? Why 24 bytes? If we used float3 particle positions, the rate would presumably be mem_bandwidth / particle_footprint. If we use a 5090, then the rate would be 1790GB/s / 12B = 146B particles / second (or 146fps of 1B particles). > non interacting particles which are extremely boring You assumed particle-particle collision above, which is expensive and might be over-kill. The top comment asked simply about the maximum rate of moving particles. Since interesting things take time & space, the correct accurate answer to that question is likely to be less interesting than trading away some time to get the features you proposed; your first answer is definitely interesting, but didn’t quite answer the question asked, right? Anyway, I’m talking about other possibilities, for example interaction with a field, or collision against large objects. Those are still physically interesting, and when you have a field or large objects (as long as they’re significantly smaller footprint than the particle data) they can be engineered to have high cache coherency, and thus not count significantly against your bandwidth budget. You can get significantly more interesting than pure advection for a small fraction of the cost of particle-particle collisions. Yes if you need rendering, that will take time out of your budget, true and good point. Getting into the billions of primitives is where ray tracing can sometimes pay off over raster. The BVH update is a O(N) algorithm that replaces the O(N) raster algorithm, but the BVH update is simpler than the rasterization process you described, and BVH update doesn’t have the scatter problem (write to multiple pixels) that you mentioned, it’s write once. BVH update on clustered triangles can now be done at pretty close to memory bandwidth. Particles aren’t quite as fast yet, AFAIK, but we might get there soon. |