Paper about selecting fixed point bit widths?

Oct 24, 2007 3 Replies

First reply

Duane Clark

I don't know any papers. Personally, I do an implementation of an algorithm in Matlab, first with floating point numbers, and then with integers. I can then make quick changes and graph the two implementations to compare the results. That allows me to determine how many bits I…

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Hello all,



Can anyone point me to a good general purpose paper about selecting appropriate bit-widths for a fixed point implementation of a signal processing algorithm? I've looked around and haven't found anything that describes a general methodology to use. I have implemented a design and it isn't performing as well as I would like. I suspect it has to do with some poor selection of bit slicing when it comes to multipiers and accumulators.



Thanks for your help!



I don't know any papers. Personally, I do an implementation of an algorithm in Matlab, first with floating point numbers, and then with integers. I can then make quick changes and graph the two implementations to compare the results. That allows me to determine how many bits I need for various portions of the algorithm to get acceptable results.

By the way, I tried the Matlab fixed point package, but found that the performance was too poor to use on processing even a modest sized data set, so I stick with using ordinary integers. Typically I stick a comment at the end of most lines indicating the scaling of that particular parameter.

Here is also some Matlab based toolbox, I used

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. Not very usefull for me, because it didnt convert automaticly / and sqrt, and so I also started manual transformation.

From Washington came the Precise Framework, look for it here:

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And if I remember right, there was a chapter about word length optimization in a book from some of the Lononder Imperial College (...some google-seconds later...): George Constantinides, Peter Cheung und Wayne Luk "Synthesis and Optimization of DSP Algorithms"

Florian

Try:

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-- Marco ________________________ Marc Reinig UCO/Lick Observatory Laboratory for Adaptive Optics

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