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???
11/28/07 10:43
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 		 #147493 - Source for the algorithm.
Responding to: ???'s previous message
I'm not sure I follow your method---more details would be appreciated.

I think the algorithm is described here. It's in python, but since it only consists of fairly simple steps it should be easy to translate to C or even assembly. And while python probably uses floating point numbers, the algorithm will work just as well with fixed-point numbers.

http://en.wikipedia.org/wiki/Binary_logarithm

How would this method apply to finding log base 10 of numbers between, say 200 & 50000? to 3 digit accuracy (log(30000)=4.48)

Well, once you can calculate the logarithm of a number for one base a, you can calculate the logarithm of any number for any base.

log[base x](y) = log[base a](y) / log[base a](x)

List of 30 messages in thread
TopicAuthorDate
1) Log computation, 2) LCD requirement            01/01/70 00:00      
   Yes            01/01/70 00:00      
      Why would you doubt it?            01/01/70 00:00      
      Yes            01/01/70 00:00      
         Doesn't have to be floating point            01/01/70 00:00      
            's the one            01/01/70 00:00      
               the good old Intel FP51 package            01/01/70 00:00      
         Should be in high level language, thanks..            01/01/70 00:00      
            you can steal it...            01/01/70 00:00      
               need floating-point log? - YES            01/01/70 00:00      
                  Fixed point ?            01/01/70 00:00      
                     RE: Fixed point ?            01/01/70 00:00      
                        And what is the input voltage range?            01/01/70 00:00      
                           RE: Aside: dB equivalent of voltage            01/01/70 00:00      
                              my point is...            01/01/70 00:00      
                                 Who remembers log tables?            01/01/70 00:00      
                              Already answered            01/01/70 00:00      
                        So use cB instead!            01/01/70 00:00      
                        Aside: dB equivalent of voltage            01/01/70 00:00      
   How to find log in assembly?            01/01/70 00:00      
      Hint            01/01/70 00:00      
      Math            01/01/70 00:00      
   Log calculation in ASM            01/01/70 00:00      
      Implementation and precision            01/01/70 00:00      
         Correct precision            01/01/70 00:00      
            Brilliant work            01/01/70 00:00      
               Absolutely!            01/01/70 00:00      
   Fixed-point log2, without lookup table.            01/01/70 00:00      
      To Mr Franck            01/01/70 00:00      
         Source for the algorithm.            01/01/70 00:00      

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