[fpc-devel] The "magic div" algorithm

[Ched]

Very interesting, Gareth !

Is the div-by-7 related to 2 to the 3rd ? If yes, is it possible to design a div-by-3 with similar magics ?

Cheers, Ched'



Le 03.09.21 à 15:35, J. Gareth Moreton via fpc-devel a écrit :
> Hey Marģers,
> 
> So I've been experimenting with your suggestion, and it looks like a resounding success!  I added some 
> new tests to the "bdiv" bench test to see how it performs.  16-bit multiplications don't get improved as 
> well as they could be on x86_64 because the intermediate values are all extended to 32-bit, but you can 
> still see a massive improvement on all the unsigned divisions by 7.
> 
> I'm currently running the test suite for i386-win32 and x86_64-win64, then will implement the same system 
> for AArch64. Thanks so much for spotting the improvement.
> 
> Gareth aka. Kit
> 
> P.S. I still need to work on the signed modulus at some point.