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Date: Thu, 29 Aug 2013 02:55:25 +0100
From: Rafael Waldo Delgado Doblas <>
Subject: Re: Parallella: Litecoin mining

Hello Alexander,

2013/8/29 Solar Designer <>

> Does this mean that replacing memcpy() improved the overall speed by as
> much as 15% or so?  If so, this suggests that the code wastes too much
> time copying data, and needs to be revised at higher level (than memcpy()
> itself), in addition to optimizing memcpy().
> Also, I just took a look at your currently committed code - your
> memcpy() replacement, at least at source code level, copies data byte by
> byte.  This is very slow, unless the compiler optimizes this into 32-bit
> or 64-bit loads and stores somehow.  I doubt that replacing memcpy()
> with this implementation of blkcpy() provided any speedup (but I could
> be wrong - weird things happen).
> Ideally, your blkcpy() should be a partially unrolled loop with LDRD and
> STRD instructions in it, and all of the data needs to be 8 byte aligned.

Maybe is because the memcpy it's stored in the external memory (as the rest
of libc), but I can do some test to check if it's a real improvement.

> > I'm checking the bug in the host code
> Do you mean the occasional segfault?  How are you debugging it, exactly?
> (I asked you this question a few days ago, but you did not answer.)

Sorry I didn't see it. Yes I mean the occasional segfault and yes it was
produced when a share is find, I think that I fixed it, but I'm testing it
right now.

 > and I will move to asm ASAP
> OK, although there's more we can do at C level as well.
> What portions of code will you be rewriting in asm?  Are you starting
> with inline asm or with a separate assembly source file?

I was thinking in replace the rotates by IMADD and LSR as you said
before,using inline asm.


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