[Numpy-discussion] Fixed-point arithemetic...any solution yet?

Dag Sverre Seljebotn dagss@student.matnat.uio...
Wed Dec 9 13:29:38 CST 2009


Ruben Salvador wrote:
> Hello everybody.
> 
> I've seen this question arise sometimes on the list, but don't know if 
> something has "happened" yet or not. I mean, any solution feasible to 
> use more or less right out of the box?
> 
> I'm just a hardware engineer, so it would be difficult for me to create 
> my own class for this, since my knowledge of python/numpy is very 
> limited, and, just don't have the time/knowledge to be more than a 
> simple user of the language, not a developer.
> 
> I have just come across this: 
> http://www.dilloneng.com/documents/downloads/demodel/ but haven't used 
> it yet. I'll give it a try and see how it works and come back to the 
> list to report somehow. But, is there any "official" plans for this 
> within the numpy developers? Is there any code around that may be used? 
> I just need to test my code with fixed point arithmetic (I'm modelling 
> hardware....)
> 
> Thanks for the good work to all the Python/Numpy developers (and all the 
> projects related, matplotlib and so on....) and for the possiblity of 
> freeing from matlab!!! I'm determined to do research with as many free 
> software design tools as possible....though this fixed-point arithmetic 
> issue is still a chain!

I haven't heard of anything, but here's what I'd do:

  - Use np.int64
  - Multiply all inputs to my code with 10^6
  - Divide all output from my code with 10^6
  - If you need to debug-print and array, simply define something like

FIXED_POINT_FACTOR = 10**6

def printarr(x):
     print x.astype(np.float) / FIXED_POINT_FACTOR

Or am I missing something?

-- 
Dag Sverre


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