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TIFF and LibTiff Mail List Archive

Thread

2003.09.05 18:14 "[Tiff] read in whole tiff file", by Pushkar Pradhan
2003.09.10 02:25 "[Tiff] read in whole tiff file", by Pushkar Pradhan
2003.09.10 07:03 "[Tiff] read in whole tiff file", by Andrey Kiselev
2003.09.10 13:04 "[Tiff] read in whole tiff file", by Frank Warmerdam
2003.09.10 13:20 "[Tiff] read in whole tiff file", by Tom Kacvinsky
2003.09.10 17:51 "[Tiff] read in whole tiff file", by Pushkar Pradhan
2003.09.10 18:36 "[Tiff] read in whole tiff file", by Phillip Crews

2003.09.10 18:36 "[Tiff] read in whole tiff file", by Phillip Crews

This is exactly what I wish to do: parallelize the RGB TO LHS transform. Some researchers suggested me to read in the whole image before distributing tiles/strips to different processors to achieve linear speedup. Maybe reading in the image in one call (TIFFClientOpen?) can save I/O overhead instead of multiple calls to TIFFReadTile etc.

Assuming that it's a very large image, you're probably spending the vast majority of clock time waiting for disk I/O, and doing one large I/O will probably not improve things much. A striped (RAID 0) storage array may speed it up appreciably.

For large files, and depending on your platform, I/O subsystem, and CPU speed, the following ideas may also speed up reading the TIFF file somewhat:

IIRC, you can do this in the TIFFOpen mode string ("rm" - disable memory mapping, "rc" - disable stripchop, "rmc" - disable both).

Once it is in memory, parallelizing the LHS to RGB code may make that part of the process quicker.

- Phillip