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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 09:36 "Re: OpenMP enabled libtiff", by Mat Maher

> Hello List,
> 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.
> 
> Thanks,
> Aaron

libTiff performance is governed by two factors: 
 1). Performance of disk read/writes
 2). Performance of compression/decompression routines (eg CPU) 

The latter would benefit enormously from multi-threaded implementation, BUT,
will ultimately be throttled by the former. 

There are a few simple things which could be done to improve matters:
 a). Buffer the entire file in memory for processing. HOWEVER, this would
 only work with a user switch input, as it's always possible the application
 TIFFs would be larger than available memory. 'Blasting' an entire file
 to/from disk maximises the transfer rate due to seek-times and DMA-setup
 latencies. In this scenario, you will end up reading/writing at the
 line-rate of the disk: which about as fast as you can get (and actually,
 for write operations, shows SATA as the faster medium for file sizes > SSD
 cache)
 b). Implement thread-per-strip CPU processing. 

For these changes, I actually wouldn't use OpenMP. The TIFF strip
arrangement is a perfect division for multi-threading utilisation. Trying to
multi-thread at a lower granularity than this is likely to yield lower
performance due to the compression/decompression libraries which are largely
sequential in operation. 

Mat



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