phc-discussions - Re: [PHC] [OT] Improvement to Momentum PoW

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Message-ID: <CAOLP8p5WgbTWidHQzpixXQQ2v81oi+QbgH_EC4qe=DpK2eHccw@mail.gmail.com>
Date: Tue, 28 Jul 2015 15:24:46 -0700
From: Bill Cox <waywardgeek@...il.com>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Re: [PHC] [OT] Improvement to Momentum PoW

On Tue, Jul 28, 2015 at 12:35 PM, Alan Kaminsky <ark@...rit.edu> wrote:

> On 07/28/2015 01:39 PM, Bill Cox wrote:
>
>> Here's a great link to radix-sort on GPUs
>> <https://code.google.com/p/back40computing/wiki/RadixSorting>.  These
>> guys
>> can radix-sort 1 billion 32-bit hashes per second on a $100 GPU (GTX 480).
>> After that, finding collisions is a linear pass, and can be done massively
>> in parallel at full memory bandwidth.
>>
>
> Thanks for the link, Bill. But after the list of hashes is sorted, a
> collision with a specific hash could be detected with an O(log n) binary
> search, more quickly than an O(n) linear search.
>
> --
> -Alan Kaminsky
>  Professor
>  Department of Computer Science
>  B. Thomas Golisano College of Computing and Information Sciences
>  Rochester Institute of Technology
>

Once the hashes are sorted, we can generate all the expected O(n)
collisions in a linear pass, testing each for passing the difficulty
threshold.

Bill

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