I recently got interested in helping with 0 A.D. development, especially optimization.
I was thinking how could we accelerate pathfinding and in consequence reduce lag.
It already seems quite optimized, A* with JPS optimization.
One of things that are still possible to do is to apply parallelism to pathfinding.
Toady I've found this: https://www.aaai.org/ocs/index.php/AAAI/AAAI15/paper/download/9620/9366
By using method shown in the article we could not only run many pathfinding requests in parallel, but parallelize a single pathfinding request in a GPU-friendly way.
We could use CUDA or OpenCL to implement it.
Authors of the article have achieved 30x(EDIT: actually it's only x6 speedup. See my third post.) speedup of A* algorithm, which is quite considerable, however I am not sure how much would it speedup 0 A.D. pathfinding.
I am not familiar with 0 A.D. code enough to start working on it, or even assess how much could it actually speedup 0 A.D. pathfinging.
I have found few posts from 2012 about running multiple pathfinding queries in parallel(not parallelising single request), saying that this wouldn't be really useful for players without strong GPUs or multicore processors.
https://wildfiregames.com/forum/index.php?/topic/16018-supreme-commander-2-pathfinding/&tab=comments#comment-239673
Well, today we have 2018(2019 soon), and even things as basic as desktop environments have multi core CPUs in their requirements, and most 3D RTS games have dedicated GPUs in their requirements.
Sure it would be much more useful for player with NVIDIA GTX 1080 than for player with intel i3 integrated GPU, however I think that speedup for most of players could still be considerable.
Maybe it will turn out too hard to implement, not as efficient as I assume here, not good for every player, etc...
But maybe it will turn out that it really speeds up pathfinding , at least for players with dedicated GPUs.