[Libre-soc-bugs] [Bug 782] add galois field bitmanip instructions

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=782

--- Comment #16 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #12)
> (In reply to Luke Kenneth Casson Leighton from comment #10)
> > nono, not predication, two ops in one instruction. look at the pseudocode
> > https://libre-soc.org/openpower/isa/svfparith/
> 
> will look in the morning...I thought that was just for complex numbers tho.
> GF and NTT both operate on modular integers/polynomials rather than complex
> numbers, so shouldn't need a separate element for real/imag components.

ahh, now I get what you mean!

NTT inner loop:
https://github.com/sympy/sympy/blob/68022011872a20c27abd047125e5feb8ce3289cc/sympy/discrete/transforms.py#L173

    h = 2
    while h <= n:
        hf, ut = h // 2, n // h
        for i in range(0, n, h):
            for j in range(hf):
                u, v = a[i + j], a[i + j + hf]*w[ut * j]
                a[i + j], a[i + j + hf] = (u + v) % p, (u - v) % p
        h *= 2

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