phc-discussions - Re: [PHC] TigerKDF paper and code ready for review

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Date: Fri, 7 Mar 2014 07:26:17 +0400
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] TigerKDF paper and code ready for review

Bill,

Another correction:

On Fri, Mar 07, 2014 at 06:45:52AM +0400, Solar Designer wrote:
> BTW, why do you mention 32 KiB there?  Your random lookups arena is
> only 16 KiB, and you can't make it larger than that on current CPUs with
> 32 KiB L1d cache and 2 hardware threads/core, without incurring much
> extra L1 cache thrashing.  TigerKDF's total memory usage is irrelevant.

Of course, my "TigerKDF's total memory usage is irrelevant" implies "as
long as the total memory usage is low enough that a sufficiently high
number of concurrent instances fit in global memory", which is the case
we should be considering in this context.  32 KiB is low enough (it's
twice lower than Litecoin's 128/2 = 64 KiB, considering that Litecoin is
commonly mined with 2x TMTO).  In that case, the small random lookups
arena's size is relevant, whereas the total memory usage is not (yet).

Alexander