Let's start with an announcement: SciPy now builds with Meson on Linux, and the full test suite passes!
This is a pretty exciting milestone, and good news for SciPy maintainers and contributors - they can look forward to much faster builds and a more pleasant development experience. So how fast is it? Currently the build takes about 1min 50s (a ~4x improvement) on my 3 year old 12-core Intel CPU (i9-7920X @ 2.90GHz):
As you can see from the tracing results, building a single C++ file
bsr.cxx, which is one of SciPy's sparse matrix formats) takes over 90
seconds. So the 1min 50 sec build time is close to optimal - the only ways to improve it are major surgery on that C++ code, or buying a faster CPU.