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Re: [Patch-gnuradio] gr_rotator fix/optimization

From: Dan Halperin
Subject: Re: [Patch-gnuradio] gr_rotator fix/optimization
Date: Fri, 07 Sep 2007 14:41:03 -0700
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I ran some quick trials and found that C takes around 18k (I was
surprised it was this fast, actually!) iterations for the phaser
amplitude to be off by 0.1%. So K around a hundred or a thousand should
be good.

- -Dan

Matt Ettus wrote:
> Dan Halperin wrote:
>> Two changes:
>> 1) Default phase increment changed from 1 to 0. This will not cause
>> faults and instead do nothing if the rotator phase is not initialized.
> Good idea.
>> 2) It seems like we can skip (expensive!) normalization of phase vector
>> if we simply normalize phase and increment upon setup. I suppose there
>> could be some lowest-order-bit precision errors that cause phase to
>> degrade over a super-long-running system, but we could surely at least
>> replace the current every-time normalization with normalization every K
>> calls, for large K (1 million+).
> I would keep the normalization -- it's in there because we ran into
> cases where the phasor really did decay to zero.  However, I like the
> idea of doing it every K times.  Even if K is 100 the performance impact
> will be negligible.
> Matt
> Matt

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