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Date: Fri, 6 Sep 2013 05:47:06 +0100
From: Rafael Waldo Delgado Doblas <lord.rafa@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Parallella: Litecoin mining

Hello Alexander,

2013/9/5 Solar Designer <solar@...nwall.com>

> This is a good point.  However, please note that with mining many things
> are probabilistic.  The time it'd take for us to find a share will vary.
> Although it might take e.g. 2 hours on average at the awful speed we
> currently have, it might also take e.g. 1 second if we're really lucky.
> My understanding is that when we're forced to start mining for a new
> block, we lose only a very small portion of work (and actually some
> pools accept "stale shares", I think).  On one hand, yes, our "2-hour
> average" (or whatever) period starts anew, but on the other it does not
> matter for our chances to find a share on any given second.
>
> Here's an analogy: computer hardware MTBF:
> http://en.wikipedia.org/wiki/Mean_time_between_failures
> For example, a hard disk drive might have an MTBF of 1000000 hours.
> If we replace HDDs every hour, will we never encounter a HDD failure?
> Per the MTBF model, no - we'll run into a HDD failure anyway, as long as
> the density function is not a constant zero for the 0 to 1 hour period.
> Often it is assumed to be such that we'd run into failures every
> 1000000 hours on average anyway.  And it is actually (almost) such in
> cryptocurrency mining, I think.
>

About this I need to launch a test for long time and check what happen
because if I force to epiphany cores to return 0, everything looks normal
(of course I get a lot of Rejected).

Today I have implemented a new TMTO. Now the first "NO_TMTO_GROUPS"
elements from V that the (position%TMTO_RATIO) is equal to (TMTO_RATIO - 1)
will be stored, in addition of any element that (position%TMTO_RATIO) is
equal to 0. With this TMTO implementation we can handle tmto ratios between
5 and 4. I have chosen (TMTO_RATIO - 1) because this elements should be
harder to recompute than (TMTO_RATIO - 2),(TMTO_RATIO - 3)...(2),(1).

The maximum value for NO_TMTO_GROUPS at the moment is 11.

Regards,
Rafael.

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