[L2Ork-dev] Double Precision project

[Jonathan Wilkes]

On Tue, May 8, 2018 at 12:38 PM, Giulio Moro <g.moro at qmul.ac.uk> wrote:
> I'd keep PD_FLOATSIZE, out of personal preference.

Sounds good. If anyone wants to submit a quick patch before I get to
it I'll merge it.

>
> ARM: on arm, the NEON SIMD floating point unit flushes denormals to zero and is not slowed down by NaNs (although it doesn't flush them). The VFPv3 (on the Cortex-A8floating point unit by default keeps denormals and does slow computations on NaNs, however it can be put into flush-denormals-to-zero and fast-nan mode.

It might be instructive to see the performance impact on ARM of
PD_BIGORSMALL in the few places
where it gets used. I can make some rudimentary tests later.

> Not sure what happens with the more recent armv8 NEONs and VFPv4 though.

Is there a way to take advantage of NEON for dsp perform routines
through a compiler flag? Or
would it require hand-coding some routines?

-Jonathan

>
> Giulio
>
> ________________________________________
> From: L2Ork-dev <l2ork-dev-bounces at disis.music.vt.edu> on behalf of Jonathan Wilkes <jon.w.wilkes at gmail.com>
> Sent: 08 May 2018 16:50
> To: l2ork-dev
> Subject: [L2Ork-dev] Double Precision project
>
> Hi list,
>
> We've merged one patch from Pranay's GSoC double precision project,
> and I'll be merging another one soon:
>
> https://git.purrdata.net/pranay_36/purr-data/commit/d0d6b54deb1b803c67d85bd5d123d3da98faf495
>
> I'd like to raise a few questions before we get too deep into the project:
>
> 1. We're using a macro PD_FLOAT_PRECISION to make it possible to set
> t_float precision at build time. This is the same macro katja used in
> pd double, but I noticed Pd Vanilla changed this to PD_FLOATSIZE. Does
> it matter? Related, should we go ahead and use the same macro as Pd
> Vanilla here?
>
> 2. I'm not sure I understand the comment from the old code:
>
> /* a test for NANs and denormals.  Should only be necessary on i386. */
>
> How does x86_64 instruction set change things?
>
> Also, what does ARM do here?
>
> -Jonathan
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