[Audacity-devel] Using OpenMP for spectrograms

Discussion:

Paul Licameli

2016-08-25 20:47:27 UTC

Has anyone else seen pull request 157? Someone implemented OpenMP for the
computation of spectrogram display. I will be very interested to review it
but have not yet looked. Question is whether we can make OpenMP
compilation part of our build procedures on all the platforms.

PRL

James Crook

2016-08-25 22:14:13 UTC

Permalink

Post by Paul Licameli
Has anyone else seen pull request 157? Someone implemented OpenMP for the
computation of spectrogram display. I will be very interested to review it
but have not yet looked. Question is whether we can make OpenMP
compilation part of our build procedures on all the platforms.
PRL

I saw the OpenMP code earlier today, before it became a pull request.
Looks very interesting.

The patch is small, and my initial review/eyballing suggests we could
accept the patch safely and thereby make it easier/possible for the
adventurous to use this under linux/mac.

Concerns - Does not provide OpenMP under MSVC. I think we will in time
want to offer it for Windows too, so it means (probably) some pain with
build process when we do - e.g. to support Intel compiler.

Overall I hugely welcome the idea/initiative. Spectrograms are the key
place where I would like to see speed ups. I think we will in time find
that we want to be using graphic cards for speed, but a 2x or 4x speed
up right now, even if only experimental, even if only on Linux/Mac,
would be great.

--James.

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Paul Licameli

2016-08-25 22:59:03 UTC

Permalink

I have wanted to try figuring out some OpenMP, but I'm pleased to be beaten
to it.

I understand it's good for the "embarrassingly parellel" computations in
loops.

I also understand it's not incompatible with the new C++11 standard
threading library (which is rather basic) and Intel thread building blocks
(which is a more elaborate library for task decomposition).

I have said that I would like to apply the C++ standard tasks to the
problem of anticipatory computation of the next screenful of spectrogram
during playback. Again I think it's compatible with this other work. One
thing is about faster computation, the other is about a background worker
to start that OpenMP thread team and collect its answers.

But using the fuller C++11 library is dependent on abandoning Snow Leopard.

PRL

Post by James Crook

Post by Paul Licameli
Has anyone else seen pull request 157? Someone implemented OpenMP for

the

Post by Paul Licameli
computation of spectrogram display. I will be very interested to review

Post by Paul Licameli
but have not yet looked. Question is whether we can make OpenMP
compilation part of our build procedures on all the platforms.
PRL

I saw the OpenMP code earlier today, before it became a pull request.
Looks very interesting.
The patch is small, and my initial review/eyballing suggests we could
accept the patch safely and thereby make it easier/possible for the
adventurous to use this under linux/mac.
Concerns - Does not provide OpenMP under MSVC. I think we will in time
want to offer it for Windows too, so it means (probably) some pain with
build process when we do - e.g. to support Intel compiler.
Overall I hugely welcome the idea/initiative. Spectrograms are the key
place where I would like to see speed ups. I think we will in time find
that we want to be using graphic cards for speed, but a 2x or 4x speed
up right now, even if only experimental, even if only on Linux/Mac,
would be great.
--James.
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David Engebretson Jr

2016-08-25 23:06:32 UTC

Permalink

Sounds great if it is possible. Can the data be output as text so it is accessible to us screen reader users?

Peace,
David
Bellingham, WA.

From: Paul Licameli
Sent: Thursday, August 25, 2016 1:47 PM
To: Audacity-Devel list
Subject: [Audacity-devel] Using OpenMP for spectrograms

Has anyone else seen pull request 157? Someone implemented OpenMP for the computation of spectrogram display. I will be very interested to review it but have not yet looked. Question is whether we can make OpenMP compilation part of our build procedures on all the platforms.

PRL

--------------------------------------------------------------------------------

Robert Hänggi

2016-08-26 13:35:34 UTC

Permalink

Post by David Engebretson Jr
Sounds great if it is possible. Can the data be output as text so it is
accessible to us screen reader users?

It's just a spectrum display optimization scheme.
You wouldn't profit from a textual/numerical output since it is about
the continuous spectrogram, instead of the normal waveform and you
would only have the spectrum at a single point in time.
The only thing that would make sense in this context would be to
transfer the current spectrum to a Braille display.
For instance to render the spectrum into 32 bands (for 40-character
displays) with nine levels each.

Robert

Post by David Engebretson Jr
Peace,
David
Bellingham, WA.
From: Paul Licameli
Sent: Thursday, August 25, 2016 1:47 PM
To: Audacity-Devel list
Subject: [Audacity-devel] Using OpenMP for spectrograms
Has anyone else seen pull request 157? Someone implemented OpenMP for the
computation of spectrogram display. I will be very interested to review it
but have not yet looked. Question is whether we can make OpenMP compilation
part of our build procedures on all the platforms.
PRL
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David Engebretson Jr

2016-08-26 15:37:38 UTC

Permalink

Maybe the new, cheaper, full page displays will be good for that!

Peace,
d

-----Original Message-----
From: Robert Hänggi
Sent: Friday, August 26, 2016 6:35 AM
To: audacity-***@lists.sourceforge.net
Subject: Re: [Audacity-devel] Using OpenMP for spectrograms

Post by David Engebretson Jr
Sounds great if it is possible. Can the data be output as text so it is
accessible to us screen reader users?