[libre-riscv-dev] [Bug 127] Transcendentals needed (SIN/COS/ATAN2/EXP/LOG/POW etc.)

bugzilla-daemon at libre-riscv.org bugzilla-daemon at libre-riscv.org
Tue Aug 20 04:58:59 BST 2019


http://bugs.libre-riscv.org/show_bug.cgi?id=127

--- Comment #17 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #16)
> found a pair of algorithms that look like they'd be quite useful for
> implementing trig/log/exp/hypot/hyperbolics/sqrt/rsqrt/divide:
> 
> http://perso.ens-lyon.fr/jean-michel.muller/BKM94.pdf
> 
> they are shift-add algorithms, so should be rather simple to implement.
> 
> they use a redundant number representation, so avoid needing full carry
> chains before the last stage, allowing a reduction in power and area used.

excellent.  there's a wikipedia page for the algorithm:
https://en.wikipedia.org/wiki/BKM_algorithm

which gives a lot more references.

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