Monero is switching to Cryptonight variant 4 (CNv4) in March 2019. CNv4 is based on Cryptonight-R, with some modifications. What are these modifications ?

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What are the differences between Cryptonight-R and Cryptonight v4?

They are the one and the same thing [src], just different naming.

Cryptonight variant 4 aka CryptonightR

More accurately though, CryptonightR is proof-of-concept code and Cryptonight-v4 is Monero's implementation of it [src].

This is proof of concept repository and a proposal for the next Monero PoW. 
It introduces random integer math into CryptonightV2 main loop.

...with some modifications. What are these modifications ?

Just some final tweaks from vtnerd [src]. These are not fundamental changes, rather last minute "tweaks".

These last minute tweaks ensure the original developer of the implementation hasn't also secretly developed an ASIC capable of working with the implementation, and also any other ASIC manufacturers that might have been developing an ASIC whilst the code was available before being PRed to Monero.

Of the tweaks themselves, the addition of an extra register and more memory access routines seem to be the significant tweaks.

  • "aka": Also Known As - this is in the commit message by the author.
    – jtgrassie
    Feb 22, 2019 at 20:48
  • The only changes I'm aware of to was merged into Wownero are vtnerd's tweaks (and maybe a couple of other minor bug fixes/tweaks). For all intents and purposes, they are the same, save vtnerd's tweaks.
    – jtgrassie
    Feb 22, 2019 at 20:51
  • Are you saying vtnerd's tweaks are in wownero too ? If that's the case, then they'd be the same indeed, but my understanding was that they had not been. Can you confirm ? Your wording is not clear :)
    – user36303
    Feb 22, 2019 at 21:34
  • No, I don't believe vtnerd's patch is in Wownero. Can see how my comment was misleading! Typo/ autocorrect. The only change to CN-R, that's in Monero I meant.
    – jtgrassie
    Feb 22, 2019 at 21:47
  • Reviewing vtnerd's patch, the significant part of the tweak looks to be the addition of an extra register.
    – jtgrassie
    Feb 23, 2019 at 0:48

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