[triangle-zpug] rounding errors with floating point operations

Joseph Mack NA3T jmack at wm7d.net
Sat Jul 19 21:28:21 UTC 2008


On Sat, 19 Jul 2008, Philip Semanchuk wrote:

> If I'm not mistaken, Python is limited to the accuracy of the underlying C 
> library for floating point ops. Here's a page that can probably answer your 
> question:
> http://docs.python.org/tut/node16.html

Thanks, this confirms what I know so far, which is 
comforting. I went to the Lahey compiler link where the 
author gives examples like I was trying, which in his hands 
fail but in my hands don't fail. One of the caveates is that 
in some implemenations, multiplication and division use 
double wide registers, in which the bits are all retained 
till the end, so none are lost in the middle.

This is a possible explanation for what I have, but I don't 
know enough about the linux/pentium/python/C math library to 
know if this is what I have.

Joe

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Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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