[PD] more about float limitation

[katja]

A set of 'double precision' diffs is on Pd-double github as the patch
files were applied in a single commit on vanilla 0.43 (in 2011):

https://github.com/pd-projects/pd-double/commit/982ad1aa1a82b9bcd29c5b6a6e6b597675d5f300

The patch set may need some modifications and additions to make it
work for Pd 0.46, but more important, the following was still left to
be done:

1. graceful handling of binary incompatibility between core <>
externals of different precision

2. make it work for Windows too

3. type-specify t_float literals consistently throughout the code


My focus was to make Pd work in double precision builds while at the
same time preserving all functionality and performance in single
precision builds. For Linux and OSX on Intel this was tested OK.
Nowadays one would include ARM platforms in the tests. Unlike Intel,
ARM isn't so fond of doubles, therefore it's extra important to
type-specify all t_float literals to avoid unintended conversions.

Regarding binary incompatibility between builds of different
precision, this is a serious problem which can't be resolved under the
quick-and-easy approach of specifying t_float at compile time. I would
therefore suggest that double precision binaries should not be
distributed until we have at least some method to prevent loading
externals of the wrong precision. In the meantime, the curious could
build double precision from source for evaluation, at their own risk.

Whether the benefits of double precision will outweigh the dangers, is
impossible to say because the benefits vary with the purpose someone
has for using Pd. When working on Pd-double in 2011 I was interested
in 'scientific' applications of Pd like impulse response measurement,
where double precision is crucial in some calculations. My current
focus is more on live performance and I've never felt a need for
doubles in this realm. Still I would be happy to help out with
doublyfication of Pd 0.46. Shouldn't we have freedom of precision?

By the way here's a video about precision in Pd, with the latter part
showing double precision in action:

https://www.youtube.com/watch?v=93632nc8LVs

Katja


On Mon, Feb 2, 2015 at 7:58 PM, Miller Puckette <msp at ucsd.edu> wrote:
> More than that - I'm hoping to look at Katja's version and adopt the changes,
> whether or not there turns out to be a set of formatted diffs available
> anywhere...
>
> cheers
> M
>
>
> On Mon, Feb 02, 2015 at 06:34:54PM +0000, Jonathan Wilkes via Pd-list wrote:
>> One other question: would you accept patches for Pd Vanilla that make it _possible_ to compile with t_float at double-precision (something Pd Vanilla cannot currently do)?  That would give the Pd Vanilla user the option to compile to double-precision if they wish, which IIUC is the whole point of t_float in the first place.  (Plus Vanilla users would get the small performance increase in the relevant tilde classes.)
>>