Found this page when looking for a Spigot algorithm for pi, but has also an article about using formal methods in the development of the Transputer Floating Point Unit.
Cool page about (semi)numerical algorithm, including a book in progress, an open source library and a number of interesting links. Also has a mirror of hakmem. The author has also published a book about pi.
Self-initializing quadratic sieve (SIQS), on a 2GHz Opteron, a 95 digit factorization takes 4 hours, and a 100-digit factorization takes just under 12 hours (possibly more). Public domain library for integer factorization, implementing Pollard-rho, ECM, self-initializing Quadratic Sieve and parts of NFS.
On 2022-06-21, the original page http://www.boo.net/~jasonp/qs.html is off-line: "All Delmarva Online services have been discontinued. December 27, 2014"
With the help of http://web.archive.org/web/20110723030828/http://www.boo.net/~jasonp/qs.html, I could locate the repository https://sourceforge.net/projects/msieve/files/msieve/ which has been updated 2016-11-11. I changed the URL for the bookmark to the sourceforge repository.