[Numpy-discussion] Different results from repeated calculation

Keith Goodman kwgoodman at gmail.com
Mon Jan 29 13:12:19 CST 2007


On 1/29/07, Charles R Harris <charlesr.harris at gmail.com> wrote:

> That's odd, the LSB bit of the  double precision mantissa is only about
> 2.2e-16, so  you can't *get* differences as  small as 8.4e-22 without about
> 70 bit mantissa's. Hmmm, and extended double precision only has 63 bit
> mantissa's. Are you sure you are computing the error correctly?

That is odd.

8.4e-22 is just the output of the test script: abs(z - z0).max(). That
abs is from python.


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