google-deepmind/alphatensor

4x4x4 algorithm for real arithmetic?

a1880 opened this issue · 1 comments

a1880 commented

From your article, I was hoping to find an algorithm for the 4x4x4 case with 47 products.
However, the article presents a mod 2 algorithm. In your factorizations collection of real arithmetic algorithms, the 4x4x4 case has 49 products. Recursive application of the 2x2x2 Strassen algorithm also requires 49 products.

Do you actually have an algorithm which outperforms recursive Strassen for the general 4x4x4 case?

From the paper it is only 47 for the case of mod 2 over z2/n and is non-commutative. Stothers' thesis allows for 48 multiplications.