GPU Acceleration of SDF gen

[sjkelly]

I looked at CUDA, Vulkan, and OpenCL. It is important this runs on most hardware, so CUDA is not an option initially unless we have several backends, which is not a priority right now. Vulkan compute kernels made my eyes bleed. OpenCL might be the best option for this.

Open question and testing is whether or not to use CLArrays or OpenCL.

[sjkelly]

It should be trivial to support threads. In the meantime, the OpenCL requirement should be soft, since it doesn't support all geometries yet and I also have issues with running on Intel Iris.

In the meantime do you have mesa-opencl-icd installed? Also, which GPU do you have?

[sjkelly]

The problem is that the OpenCL back end is not very abstract. It is a kernel compiler and not a transpiler, so some geometries are unsupported in the OpenCL back end. I only can run it on one out of three of my development environments. I have multithreadin and SIMD working now which had very nice performance gains of 12x on 4 threads. This puts it within the same order of magnitude as the GPU performance for most geometries. The bottleneck is still the meshing component, but I have run into some bugs in the multithreading paradigms with the meshing algorithms that may block this.

[sjkelly]

Also OpenMPI is very good alternative for very high resolution solid models. From what I understand Julia has a native distributed arrays mechanism that is similar to OpenMPI.
Still the bottleneck will be the memory use in the current implementation. I have some ideas to minimize the memory allocation from nxnynz to nxny2, but I have to rework Meshing.jl before that is possible.

[sjkelly]

@scheming-pony if you want to checkout the sjk/simp branch and checkout master for Meshing, this should work now. I'm shaking down Meshing a little longer before I tag a new release and merge my branch into Descartes.

[sjkelly]

👍

I am hoping to add some docs soon for the user-facing API. There will be some code churn in everything else. Please let me know if you have and questions or feature requests.