This is probably a $y=f(x)$ question, but I searched several times on the MathOverflow without success so I decided to explicitly ask for the help of other members: please feel free to ask me to remove the question if inappropriate.  

Nearly a month or so, in a MathOverflow answer (I guess so, but at this point I should consider the possibility I am wrong) to a question on (computational) number theory I read about a C library for arbitrary precision arithmetic which was successfully used in several research papers, including one where the Authors proved the existence of a soliton solution to a PDE by proving the strict positivity of a term by estimating its size as being not less than a $21$ bit mantissa multiplied by $10^{-5000}$ (I am fairly sure of this fact but, as already said, I should consider the possibility I am wrong). I went to the library web page and saved the link in my bookmarks: then a crash occurred (yes, also experienced electronics engineers lose data...) and up until now I was not able to find the former Q&A.


**Question**: can someone provide me a reference to this library?
  




On a fast high precision numerical analysis C library
Since you speak about mathematical proofs, probably you don't want an arbitrary-precision library, but a verified computation library based on interval arithmetic.


Maybe [Arb](https://arblib.org/)? Or [boost-interval](https://www.boost.org/doc/libs/1_82_0/libs/numeric/interval/doc/interval.htm)?


And maybe the post you remembered is about Warwick Tucker [proving](https://mathoverflow.net/a/123683/1898) the existence of the Lorenz attractor.


