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Date: Thu, 29 Aug 2013 00:11:56 +0100
From: Rafael Waldo Delgado Doblas <>
Subject: Re: Parallella: Litecoin mining

Hello Alexander,

2013/8/25 Solar Designer <>

> I took a look at your committed code - it tries to use TMTO 5, but it
> just gets stuck somewhere.  So I've just spent an hour playing around
> with it, optimizing its memory usage.  Please see the attached patch.
> With this patch, the code + read-only data size is reduced by about 1700
> bytes, and it pretends to work, but when I enable the debugging output
> in driver-epiphany.c, the hashes computed on ARM and Epiphany don't
> match.  Moreover, they don't match even if I reduce TMTO to 6 (and
> adjust DIVTMTO accordingly).  My guess is that you had introduced some
> bug, so I am leaving it up to you to debug it. ;-)  It is, of course,
> also possible that the bug is in my patch.

The problem was in RNDr macro. The loop that call the RNDr macro only cares
about the first line of RND (macro inside of RNDr), because a missing keys
{ }. After I fixed this small bug the performance is ~1.3K/h (also I have
replaced the memcpy by a own made function because it adds 0.2K/h,
increasing 8 bytes).

I'm checking the bug in the host code and I will move to asm ASAP, the
optimistic performance would be 1.7K/h. Not bad if finally the 1024 core
CPU is released.


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