[surface] Reduce time taken in TextureMapping::sortFacesByCamera from O(faces*points) to O(faces)
#3981
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Morwenn
reviewed
Apr 27, 2020
kunaltyagi
reviewed
Apr 28, 2020
kunaltyagi
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changelog: enhancement
kunaltyagi
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kunaltyagi
changed the title
TextureMapping::sortFacesByCamera from O(faces*points) to O(faces)
kunaltyagi
approved these changes
Apr 29, 2020
kunaltyagi
added
needs: code review
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I didn't look at the lambda but indeed: currently every capture is copied into the lambda, which looks needlessly expensive here. If I'm not mistaken it's even copied at each iteration. |
@kunaltyagi @Morwenn Just committed again. I had errors compiling at first with the [&] but that has been fixed. I've changed it back to [&] now and it works. Thanks for the corrections! |
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Please rebase so we can test on the now working Mac and Ubuntu 20.04 CI |
… to be an unordered set. Previously, the system was checking through a vector in O(n), but now it's going much faster at approximately O(1).
… method than before as per @Morwenn 's suggestion
… errors led me to believe that I needed to list all captures, but now that those other errors have been ironed out, @kunaltyagi and @Morwenn have pointed out that that was unnecessary and is in fact computationally wasteful.
SergioRAgostinho
approved these changes
May 6, 2020
SergioRAgostinho
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needs: author reply
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Note: squash and merge |
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For large meshes, the old code was prohibitively slow, and had a TODO to address that. Changing from a vector to an unordered_set reduces the outer loop's complexity from O(N*M) to O(N) where N is the number of faces in a mesh and M is the number of points in the point cloud.
On the sample mesh I was using, I reduced the processing time for 3 test images from over 20 minutes to under 2.