Kiwi is an efficient C++ implementation of the Cassowary constraint solving
algorithm. Kiwi is an implementation of the algorithm based on the seminal
Cassowary paper. It is not a refactoring of the original C++ solver. Kiwi has
been designed from the ground up to be lightweight and fast. Kiwi ranges from
10x to 500x faster than the original Cassowary solver will typical use cases
gaining a 40x improvement. Memory savings are consistently > 5x

Homepage:
https://github.com/nucleic/kiwi
