Dolfin version 2019.2.0.dev0

Great you found the patch you need already. In general you should find the new version performs more effectively*.

In regards to reverting to old versions, it’s not so simple. One option is to dig into the build records on the PPA (look for the “View all builds” link, filter on “Successfully built”). e.g. https://launchpad.net/~fenics-packages/+archive/ubuntu/fenics/+build/18158564 . Download the .deb files for the old version, then install manually with sudo dpkg -i *.deb.

It’s possible to place packages in a Hold state to keep them from automatically upgrading. apt can also be configured to pause and show the list of packages to be upgraded before proceeding with the upgrade, giving you a chance to cancel the upgrade (e.g. to place individual packages on Hold).

* To get best performance, you’ll probably want a tuned BLAS library to be installed, such as openblas or blis, rather than the reference implementation libblas-dev.