[Radiance-general] parallel dctimestep

[Greg Ward]

Hi Santiago,

A research assistant at LBNL spent some time implementing a GPU version of dctimestep, and found that the process was i/o-bound, meaning that the matrix multiplications, etc. took much less time to do that just loading the input and writing out the result.  His process was still a bit faster than the original dctimestep, but since then, I implemented some optimizations to avoid multiplying zero rows and vectors (mostly nighttime points from gendaymtx), which meant the GPU implementation was really no faster.

If you have an SSD or RAMdisk for i/o, then you may yet eek some benefit from running the calculation in parallel, but you'd have to interleave the matrices in the end or handle subsequent calcs by month.  Interleaving would probably require transposing each matrix, concatenating, then transposing the result.  It's all doable with rcollate, but that will take a bit of time as well.

Cheers,
-Greg

> From: Santiago Torres <Santiago.Torres at arup.com>
> Date: September 22, 2017 7:55:53 AM PDT
> 
> Dear all,
> 
> This might be a silly question, but I couldn't find any reference. Is there a way to run dctimestep in parallel?
> 
> Or, would it be possible to create a weather tape for each month, create a matrix from each, and run each month separately?
> 
> Thanks,
> Santiago