pass use_pba to mapper to use GPU

[oldshuren1]

No description provided.

[reynoldscem]

I've made a similar change locally. It's worth noting that if your problem gets big enough COLMAP will fall-back to the CPU version of PBA which is ~an order of magnitude slower. You can remove the check in COLMAP to always use the GPU if you are comfortable with risking the worse numerical stability.

[oldshuren1]

Think you mean in controller/incremental_mapper.cc:68 checking for ParallelBundleAdjuster::IsSupported?

I also found that if the camera mode is single, pba is also not used. But using single camera itself can reduce a lot of time.

[reynoldscem]

No I don’t mean that. There’s a check on the number of residuals in the problem hardcoded. I’ll have a look for it on Monday if you can’t find it.

[sarlinpe]

Since IncrementalMapperOptions has many other useful options, I would prefer to instead provide a flexible mechanism to modify any of these options from the command line, just like COLMAP accepts --Mapper.ba_global_pba_gpu_index 1. This could be later extended to the ImageReaderOptions.

[sarlinpe]

This should be solved by #210. Can you please confirm that it works for you?