[Numpy-discussion] Time for beta1 of NumPy 1.0

David M. Cooke cookedm at physics.mcmaster.ca
Fri Jun 30 13:59:28 CDT 2006


On Fri, 30 Jun 2006 14:42:33 -0400
"Jonathan Taylor" <jonathan.taylor at utoronto.ca> wrote:

> +1 for some sort of float.  I am a little confused as to why Float64
> is a particularly good choice.  Can someone explain in more detail?
> Presumably this is the most sensible ctype and translates to a python
> float well?

It's "float64", btw. Float64 is the old Numeric name.

Python's "float" type is a C "double" (just like Python's "int" is a C
"long"). In practice, C doubles are 64-bit.

In NumPy, these are the same type:
float32 == single   (32-bit float, which is a C float)
float64 == double   (64-bit float, which is a C double)

Also, some Python types have equivalent NumPy types (as in, they can be used
interchangably as dtype arguments):
int   ==   long        (C long, could be int32 or int64)
float ==   double
complex == cdouble     (also complex128)

Personally, I'd suggest using "single", "float", and "longdouble" in numpy
code.

[While we're on the subject, for portable code don't use float96 or float128:
one or other or both probably won't exist; use longdouble].

-- 
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|David M. Cooke                      http://arbutus.physics.mcmaster.ca/dmc/
|cookedm at physics.mcmaster.ca




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