Re: [postgis-users] how many min. floating-points?

John Smith wrote:
> guys,

Please don't cross-post, especially since nobody on the PostGIS mailing
list answered your previous question.

> how many min. floating-points must a server hardware support for
> postgresql+postgis? does postgresql+postgis do much floating-point
> math to make a difference? can someone give postgresql+postgis
> application examples that will require high floating-points?

I don't know what you mean by "floating points". I've never heard it
used in the sense of a countable quantity.

From the manual:

"The data types real and double precision are inexact,
variable-precision numeric types. In practice, these types are usually
implementations of IEEE Standard 754 for Binary Floating-Point
Arithmetic (single and double precision, respectively), to the extent
that the underlying processor, operating system, and compiler support it."

...

"On most platforms, the real type has a range of at least 1E-37 to 1E+37
with a precision of at least 6 decimal digits. The double precision type
typically has a range of around 1E-307 to 1E+308 with a precision of at
least 15 digits. Values that are too large or too small will cause an
error. Rounding might take place if the precision of an input number is
too high. Numbers too close to zero that are not representable as
distinct from zero will cause an underflow error."

I think you would have to have some *very* complicated geography in
order to make PostGIS generate non-negligible floating point-related
imprecision.

Find more information about PostgreSQL and numeric data types at the
following URL.

http://www.postgresql.org/docs/8.3/static/datatype-numeric.html

Colin