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Re: [Discuss-gnuradio] Logarithmic algebra for FIR calculation?
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] Logarithmic algebra for FIR calculation? |
Date: |
Tue, 20 Jun 2006 10:41:23 -0700 |
User-agent: |
Mutt/1.5.9i |
On Tue, Jun 20, 2006 at 09:32:48AM -0700, Johnathan Corgan wrote:
> I was Googling around on constant modulus stuff and came across the
> following paper:
>
> http://www.ee.ucl.ac.uk/lcs/papers2002/LCS133.pdf
Thanks for the pointer.
> But it wasn't the CMA stuff that caught my attention, it was the
> description of converting a transversal FIR filter from a MAC function
> to an adder by going into the logarithmic domain, delay/adding the
> (log)weights, then exponentiating. This appeared to be done with fixed
> point integers. The log operation was approximated.
>
> I'm not all that familiar with optimized floating point (it just works)
> so I don't know how long SSE, etc. multiplies take, but I am interested
> in knowing whether there is merit to this transform in time and MIPS for
> a float based signal stream on a x86 processor such as we use in GNU Radio.
Floating point is very fast. We can do pretty close to 1 MAC / clock cycle
on Pentium 3/4/M, Athlon and AMD-64.
> -Johnathan, posting from sunny, 109F Phoenix "but it's a dry heat" AZ :-(
Eric