http://benji3up2kxewkqfcq7buxk2xd6zwy3zggnurkrm3l4cvwy2iipvyyad.onion/mirrors/gmpdoc/Toom-3_002dWay-Multiplication.html
The interpolation is then identical, and in fact
the same toom_interpolate_5pts subroutine is used for both squaring and
multiplying. Toom-3 is asymptotically O(N^1.465 ) , the exponent being log(5)/log(3) , representing 5 recursive multiplies of 1/3 the
original size each.