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January 2016

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2016.01.25 18:25 "OpenMP enabled libtiff", by Aaron Boxer
2016.01.25 19:05 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.25 19:17 "Re: OpenMP enabled libtiff", by <kandel3@illinois.edu>
2016.01.25 19:18 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.25 20:21 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.25 20:45 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.25 23:27 "Re: OpenMP enabled libtiff", by <kandel3@illinois.edu>
2016.01.26 09:12 "Re: OpenMP enabled libtiff", by <jcupitt@gmail.com>
2016.01.26 13:45 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.26 14:46 "Re: OpenMP enabled libtiff", by Olivier Paquet
2016.01.26 16:01 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.26 17:10 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.26 19:32 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.26 19:29 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.26 20:36 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.27 18:32 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.27 19:55 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.29 13:28 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.29 14:46 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.29 15:48 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.29 15:49 "Re: OpenMP enabled libtiff", by Aaron Boxer
2016.01.29 18:12 "Re: OpenMP enabled libtiff", by Bob Friesenhahn
2016.01.26 09:36 "Re: OpenMP enabled libtiff", by Mat Maher
2016.01.26 09:52 "Re: OpenMP enabled libtiff", by Even Rouault
2016.01.26 14:22 "Re: OpenMP enabled libtiff", by Fred Rothganger
2016.01.27 18:51 "Re: OpenMP enabled libtiff", by Larry Gritz

2016.01.26 09:12 "Re: OpenMP enabled libtiff", by <jcupitt@gmail.com>

On 25 January 2016 at 18:25, Aaron Boxer <boxerab@gmail.com> wrote:
> Is anyone interested in having OpenMP support in libtiff ?
> Is this feasible?  I am planning on adding this feature for another project
> I am working on, so I am trying to gauge interest.

I think I would not add openmp support directly. Scattered reads and
writes are too difficult to support efficiently with the current
structure.

Instead, as Bob said, I think I would split the library in two. Have a
very low level interface which just reads or writes compressed strips
or tiles, essentially just a thin wrapper around the read() and
write() system calls, and then have a higher layer to do compression,
decompression, packing and unpacking. The low-level read/write layer
should be single-threaded, the higher layer should be threadsafe.

Now you can serialize read/write to match the disc structure, but the
application can use SMP in whatever framework it prefers to accelerate
the CPU-intensive parts.

Uncompressed tiffs already work rather like this: if you call
TIFFReadEncodedStrip() on an uncompressed image, it's just a few
function calls around read() --- it's very easy to saturate any disc
system. We just need to move the decompress stage outside the serial
code path.

John
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