You can always emulate FP64 - it is not performant to do so, but since CFD is essentially memory-bandwidth-bottlenecked rather than limited by shader performanc

You can always emulate FP64 - it is not performant to do so, but since CFD is essentially memory-bandwidth-bottlenecked rather than limited by shader performance, this probably is not a big concern. You've got shaders sitting around waiting anyway. The M1 architecture only allows the CPU to access a fraction of the memory bus, it is around 25% of the total bandwidth or so iirc. The rest has to go to the GPU or NPU or one of the other units, so even if your FP64 code was super shitty emulated with no hardware support, on paper you should be able to quadruple performance by utilizing it. If you can "pre-digest" it at all, and then push it back from the GPU to the CPU, that might be another viable approach. Of course none of this will exist out of the box in some 90s FORTRAN code!