Support for Ceres 2.1.0

[Kaapeine]

The latest version of Ceres comes with CUDA support for DENSE_SCHUR solvers. This might make a significant improvement to the speed of the optimization. Just posting this here in case someone wants to take up the task of getting VINS to work on this version of Ceres. I'd try but my knowledge of Ceres is limited. Any suggestions are welcome, I might give it a shot.

[Kaapeine]

So an update to this: VINS-Fusion-GPU supports Ceres 2.1.0 without any requiring any change in code. I was able to enable CUDA by adding this line to the optimization method in Estimator.cpp.
options.dense_linear_algebra_library_type = ceres::CUDA;

However, I wasn't able to see much of an improvement in performance but somebody else might be able to. @pjrambo can I create a PR for this? :D

[JACKLiuDay]

Hi, thank you for you great work. I noticed about ceres 2.1 supported for cuda. And I want to apply vins-fusion on Nvidia NX. While without the GPU or cuda, CPU of NX is strenuous to run vins-fusion. The CPU occupancy rate is high to 60%-70%. I will try to test the vins-fusion on NX with ceres2.1 for cuda.

[sun421-cloud]

Hi, thank you for you great work. I noticed about ceres 2.1 supported for cuda. And I want to apply vins-fusion on Nvidia NX. While without the GPU or cuda, CPU of NX is strenuous to run vins-fusion. The CPU occupancy rate is high to 60%-70%. I will try to test the vins-fusion on NX with ceres2.1 for cuda.

Hello, I am trying to apply vins-fusion on Nvidia orin NX now. I would like to ask what the result is after you change the version of the ceres?