hi Erland, On Tue, Jun 17, 2008 at 2:04 AM, Erland Lewin <[EMAIL PROTECTED]> wrote:
> Hello Saurabh, > > 2008/6/16 saurabh gupta <[EMAIL PROTECTED]>: > >> So, I have written fixed point codes in which all calculations are handled >> through fixed point. I have used the 16:16 notation for fixed point and used >> 32 bit integer to represent a fixed point. > > > FWIW, when I wrote an embedded speech recognition engine, I used 16 bits > for most of the data in the models etc. If you could manage to store values > in 16 bits rather than 32, then I your memory requirements could be halved, > and probably performance increase significantly, since the cpu to memory > bandwidth would be lower, and I think that might be a performance > bottleneck. However, it required careful tracking of what range of values > were actually required in various stages of the algorithm. > This was the point where I thought this way. Please correct me if I am wrong. Since the word length of ARM processor of FR is 32bit, I chose 32 bit size for the fixed point notation. In using 32 bit fixed point notation, my range of both integer and fraction part also increases. > > > Multiplication and division procedures for fixed point are implemented >> through macros. As the project progresses, the stress will be given to >> optimize the codes >> more. > > > I hope you won't have to do much if any division because division is quite > slow. If there are variables you need to divide by, try storing 1/x instead > of x, and then doing multiplication instead of division if you can manage > that. > I did do that whenever I had to divide by the constant numbers. But at some points, the situation happens to perform the division by run time variables and so, I had to implement the fixed point division too. > > > Good luck, > > Erland > > > > _______________________________________________ > Openmoko community mailing list > community@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/community > > -- Saurabh Gupta Electronics and Communication Engg. NSIT,New Delhi
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