[Discuss-gnuradio] Logarithmic algebra for FIR calculation?

[Johnathan Corgan]

I was Googling around on constant modulus stuff and came across the 
following paper:

http://www.ee.ucl.ac.uk/lcs/papers2002/LCS133.pdf

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.

I also wonder how long through a flow graph one could stay in the 
logarithmic domain.

-Johnathan, posting from sunny, 109F Phoenix "but it's a dry heat" AZ :-(