catkin pkg config template: performance fix for pack/unpack/append #1137
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
These algorithms may be used O(M^2) times where M is the level of rospackage nesting, and each pack/unpack/append algorithm complexity are O(N^2)/O(N)/O(N^2) where N is libraries count. The fix allows to reduce them to O(1) complexity if we only consider amount of cmake statements executed. Notes regarding REMOVE_DUPLICATES in list_append_unique and list_append_deduplicate are incorrect, in case of: - list_append_unique: REMOVE_DUPLICATES uses set/unordered_set to remember encountered items, all output items are written in order, so the algorithm is "stable", it doesn't shuffle elements - list_append_deduplicate: REMOVE_DUPLICATES is improper here, as it removes duplicates from the added element list, not the added-to element list, not due to it's "unstability" as note suggests 3.0.2: https://github.com/Kitware/CMake/blob/v3.0.2/Source/cmListCommand.cxx#L480-L493 3.19.6: https://github.com/Kitware/CMake/blob/v3.19.6/Source/cmAlgorithms.h#L120-L130
aurzenligl
force-pushed
the
aurzenligl/pkg-config-speedup
branch
from
234f866
to
03b9647
Compare
|
@tfoote, @mjcarroll, should I open an issue associated with the PR? |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
rationale
These algorithms may be used O(M^2) times where M is the level of rospackage nesting, and each pack/unpack/append algorithm complexity are O(N^2)/O(N)/O(N^2) where N is libraries count. The fix allows to reduce them to O(1) complexity if we only consider amount of cmake statements executed. In a ros distro where level of nesting may exceed 10 and library count a couple of hundreds, cmake execution time can easily take more than 30 seconds, which becomes prohibitive.
reproduction
https://github.com/aurzenligl/study/tree/master/ros-catkin-pkgconfig
notes
Notes regarding REMOVE_DUPLICATES in list_append_unique and list_append_deduplicate are incorrect, in case of:
3.0.2: https://github.com/Kitware/CMake/blob/v3.0.2/Source/cmListCommand.cxx#L480-L493
3.19.6: https://github.com/Kitware/CMake/blob/v3.19.6/Source/cmAlgorithms.h#L120-L130