My reading of the paper is that the new 4x4 algorithm only works in Z/(2), where there are no issues of roundoff errors. (Z/(2) is the field of integers modulo

My reading of the paper is that the new 4x4 algorithm only works in Z/(2), where there are no issues of roundoff errors. (Z/(2) is the field of integers modulo 2.) The paper seems to say that for real numbers, Strassen is still the best known algorithm for the 4x4 case. (Disclaimer: googler, I have nothing to do with this research.)