linux-kernel - Re: [Cbe-oss-dev] [RFC, PATCH 4/4] Add support to OProfile for profiling Cell BE SPUs -- update

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Message-ID: <20070131122533.5ef22907@localhost>
Date:	Wed, 31 Jan 2007 12:25:33 +1100
From:	Christian Krafft <parabelboi@...serverein.de>
To:	Carl Love <cel@...ibm.com>
Cc:	maynardj@...ibm.com, linuxppc-dev@...abs.org,
	oprofile-list@...ts.sourceforge.net, cbe-oss-dev@...abs.org,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [Cbe-oss-dev] [RFC, PATCH 4/4] Add support to OProfile for
 profiling Cell BE SPUs -- update

On Tue, 30 Jan 2007 15:31:09 -0800
Carl Love <cel@...ibm.com> wrote:

> An LFSR sequence is similar to a pseudo random number sequence. For a 24
> bit LFSR sequence each number between 0 and 2^24 will occur once in the
> sequence but not in a normal counting order.  The hardware uses the LFSR
> sequence to count to since it is much simpler to implement in hardware
> then a normal counter.  Unfortunately, the only way we know how to
> figure out what the LFSR value that corresponds to the number in the
> sequence that is N before the last value (0xFFFFFF) is to calculate the
> previous value N times.  It is like trying to ask what is the pseudo
> random number that is N before this pseudo random number?

That should be no problem. 
You can just revers your algorithm and let it run x times instead of 0xFFFFFF-x.

> 
> I will add a short comment to the code that will summarize the above
> paragraph.
> [snip]
> 
> _______________________________________________
> cbe-oss-dev mailing list
> cbe-oss-dev@...abs.org
> https://ozlabs.org/mailman/listinfo/cbe-oss-dev

-- 
Mit freundlichen Grüssen,
kind regards,

Christian Krafft
IBM Systems & Technology Group, 
Linux Kernel Development
IT Specialist
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