A bit tangential, but the folks behind the GNU Multiple Precision Library (GMPLib) have the problem of choosing algorithms more or less fleshed out. They've got some fairly approachable manual pages[1] for the various algorithms they use as operand sizes scale up, where Karatsuba is only the second of six options in terms of operational complexity.
This really demonstrates the utility of pulling in a library written by experts in the field the library handles.