Maamoun TK <maamoun...@googlemail.com> writes: > On Sat, Oct 29, 2022 at 11:31 AM Niels Möller <ni...@lysator.liu.se> wrote: > >> I think I'd like to merge the multi-block refactoring branch >> (refactor-poly1305) before your radix 2^44 code. But that breaks current >> power assembly, since that branch currently requires that any assembly >> code for poly1305 implements both functions. I see three options: >> >> 1. Implement multi-block radix 2^64 code for ppc. Might not be well >> spent time if it's going to be much slower than new radix 2^44? >> >> 2. Implement multi-block radix 2^64 in ppc assembly, but just as a loop >> around the single block function (so no speedup). >> > > I apologize for late reply, I don't feel well today.
I hope you feel better soon. > I don't understand the difference between the two options. I was thinking abotu (1) proper implementation, keeping state in registers through out the loop, and (2) something as simple as possible, with a loop just making an explicit call to the single-block function. But I'm now leaning towards option 3: Somehow reorganize things so that asm implementation of multi-block function is optional (could be a separate file, or changes to how the HAVE_NATIVE_* constants are defined (currently, they're only set for optional asm fils, not for asm files replacing C files). I think that will also make it more straight forward to measure performance benefit of implementing the multi-block function when adding poly1305-assembly for other archs later. > And do you prefer to have the code of 2^64 for multi-block over 2^44? 2^44 looks very promising, so I don't think we should spend much more time on 2^64 for ppc. But I still want to find a way to merge the refactoring branch without breaking the ppc build (in the current state, the branch fails with link errors on ppc). > I mentioned the benchmark numbers of both radixes in MR description and > previous message. Single-block (2^64) achieves 658.45 Mbyte/s on POWER9 2.2 > GHz while multi-block (2^64) with a loop around it in assembly achieves > 1002.27 Mbyte/s and multi-block (2^44) in assembly hit 2044.05 Mbyte/s > under same circumstances. It's clear to me that radix 2^44 performs the > best for multi-block but not sure if there are other considerations for > that. Sounds great! Did 2^44 beat 2^64 also in the single block case? Do we need to consider keeping 2^64 for small-message performance? It will of course make things simpler if we can switch to 2^44 for everything (on ppc). Regards, /Niels -- Niels Möller. PGP key CB4962D070D77D7FCB8BA36271D8F1FF368C6677. Internet email is subject to wholesale government surveillance. _______________________________________________ nettle-bugs mailing list -- nettle-bugs@lists.lysator.liu.se To unsubscribe send an email to nettle-bugs-le...@lists.lysator.liu.se
