"Printing Floating-Point Numbers Quickly and Accurately"
mwh at python.net
Sat Jul 24 18:01:00 CEST 2004
Tim Peters <tim.peters at gmail.com> writes:
> [Michael Hudson]
> > Does anyone (Tim?) have (ideally Python, but I can cope) code
> > implementing the fixed-format algorithm from the Subject: named paper
> > by Burger & Dybvig?
> I don't, and you're too young if you think anyone else might <wink>.
> The paper gives Scheme code, you know!
Not for the fixed format algorithm it doesn't. The paper says:
The rational arithmetic used in fixed-format printing can wbe
converted into high-precision integer arithmetic by introducing a
common denominator as before. Because there are several more cases
to consider, however, the resulting code is lengthy and has
therefore been omitted from this paper.
I was hoping someone else had considered all the cases for me :-)
I've already translated the free format code from the paper into
Python, unfortunately it's not what I actually need...
> And there's a Haskell variant here:
That's the free format algorithm again, unless I've gone blind.
> As the paper says at the end,
> [David] Gay ... showed that floating-point arithmetic is sufficiently
> accurate in most cases when the requested number of digits is small.
> The fixed-format printing algorithm described in this paper is useful when
> these heuristics fail.
> IOW, the point of Burger & Dybvig was to run faster than the
> algorithms in the earlier Steele & White paper, but David Gay's code
> *usually* beats everything on speed (if you don't care about speed,
> code for this task is quite simple; if you do care about speed, it's
> mind-numbingly complicated), so there's little incentive to implement
> this algorithm.
I'm probably suffering from an attack of perfectionism. Burger &
Dubvig's algorithm is so neat!
> Gay's code is written in C, & available from Netlib:
Now *that* code is over-the-top, even for me :-)
. <- the point your article -> .
|------------------------- a long way ------------------------|
-- Christophe Rhodes, ucam.chat
More information about the Python-list