[Numpy-discussion] Random int64 and float64 numbers

Charles R Harris charlesr.harris@gmail....
Thu Nov 5 17:36:40 CST 2009


On Thu, Nov 5, 2009 at 4:26 PM, David Warde-Farley <dwf@cs.toronto.edu>wrote:

> On 5-Nov-09, at 4:54 PM, David Goldsmith wrote:
>
> > Interesting thread, which leaves me wondering two things: is it
> > documented
> > somewhere (e.g., at the IEEE site) precisely how many *decimal*
> > mantissae
> > are representable using the 64-bit IEEE standard for float
> > representation
> > (if that makes sense);
>
> IEEE-754 says nothing about decimal representations aside from how to
> round when converting to and from strings. You have to provide/accept
> *at least* 9 decimal digits in the significand for single-precision
> and 17 for double-precision (section 5.6). AFAIK implementations will
> vary in how they handle cases where a binary significand would yield
> more digits than that.
>
>
I believe that was the argument for the extended precision formats. The
givien number of decimal digits is sufficient to recover the same float that
produced them if a slightly higher precision is used in the conversion.

Chuck
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.scipy.org/pipermail/numpy-discussion/attachments/20091105/6debf3ff/attachment-0001.html 


More information about the NumPy-Discussion mailing list