Kiwi is a C++ implementation of the Cassowary constraint solving algorithm. Kiwi is an implementation of the algorithm based on the seminal Cassowary paper, but it is not a refactoring of the original C++ solver. Kiwi ranges from 10x to 500x faster processing than the original Cassowary solver with the same input set, with typical use cases gaining a 40x improvement. Memory savings are consistently >5x.
In addition to the C++ solver, Kiwi ships with hand-rolled Python bindings.