Not so fast: it&#x27;s possible to have library-level fault tolerance, or OS-level fault tolerance, that is implemented in software, without having to change the source code much or at all.<p>My perspective on this is informed by work on ABFT (for more on that, see <a href="https:&#x2F;&#x2F;www.computer.org&#x2F;csdl&#x2F;trans&#x2F;tc&#x2F;1984&#x2F;06&#x2F;01676475.pdf" rel="nofollow">https:&#x2F;&#x2F;www.computer.org&#x2F;csdl&#x2F;trans&#x2F;tc&#x2F;1984&#x2F;06&#x2F;01676475.pdf</a>, and the literally 1000 later papers citing it) -- you can design a version of the basic linear algebra subroutines that have fault-tolerance built in, and use them without changing program source code.<p>For codes that spend a lot of time doing numerical computations (e.g., preliminary data reduction in a spacecraft on-board computer), ABFT is an interesting option.