Strassen algorithm

Summary

The Strassen algorithm multiplies two $n \times n$ matrices with $O(n^{\log_2 7})$ arithmetic operations, where $\log_2 7 \approx 2.807$. It rests on a way to multiply $2 \times 2$ matrices with $7$ multiplications instead of $8$, applied recursively to blocks. Published by Volker Strassen in 1969, it was the first method faster than the usual $O(n^3)$ matrix multiplication. It started the search for the matrix multiplication exponent.