Leith, For the record, I've just made changes in the development version that allow specifying more than 2 GB (the effective value might be 2GB or 3GB on 32 bit operating systems). See http://trac.osgeo.org/gdal/ticket/3689
And the current limit is 2047, not 2147. (2147 * 1024 * 1024 is a negative value, so the effect should be to have a 0-byte cache... This was a typo in the doc at http://trac.osgeo.org/gdal/wiki/ConfigOptions) As you've noticed gdal_merge is not able to merge big images without requiring big amount of RAM. You can try gdalwarp instead. Best regards, Even Le dimanche 18 juillet 2010 06:44:20, Leith Bade a écrit : > That seemed to do the trick. It finished overnight, a lot faster than > before. > > Final file was 83GB. (Only 1/2 the dataset was used) > > Is there a reason GDAL_CACHEMAX 2147 is the maximum? Under 64-bit a 32-bit > process has 4GB of virtual memory rather than 2GB under 32-bit (or 3GB with > the /3GB Windows boot switch). > > I was successfully able to use kdu_compress on the result as well so now I > only need 4GB to store the file! (Although kdu_compress also has a memory > limit at 2GB, but you can flush the codestream after every tile to fix > that). > > Thanks, > Leith Bade > [email protected] > > On 17 July 2010 15:29, Greg Coats <[email protected]> wrote: > > Since you have 4 GB RAM, I suggest overriding the 40 MB GDAL_CACHEMAX > > default, and increasing it > > gdal_merge.py --config GDAL_CACHEMAX 1000 > > The maximum possible GDAL_CACHEMAX is > > gdal_merge.py --config GDAL_CACHEMAX 2147 > > Greg > > > > On Jul 16, 2010, at 9:19 PM, Leith Bade wrote: > > > > Hi, > > > > I am trying to use gdal_merge to mosaic a very large topo GeoTIFF set. > > > > Uncompressed the data set is 60GB, but I keep it stored with DEFLATE > > compression which results in a dataset under 10GB. > > > > Mosaicked the uncompressed file will be 125GB because of the large > > regions of nodata generated. Unfortunately this is too big to store on > > my HDD so I need to apply DEFLATE to it as well. > > > > I am experimenting with only 1/2 the data set at the moment with this > > command: > > gdal_merge -co COMPRESS=DEFLATE -co ZLEVEL=9 -co BIGTIFF=YES -o NI-50.tif > > *-00.tif > > > > On my AMD Phenom II X4 @ 3.2GHz, 64 bit Windows 7, 4GB DDR3 CAS-7 RAM > > (basically a decently specced PC gaming machine) > > it has been running for 16 hours and so far has only made it 60% (124 of > > 204 files) > > > > The other issue is so far the file is 54GB so I will likely run out of > > disc space before it finished. This indicates that no DEFLATE > > compression is happening at all! > > > > It currently maxing only 1 CPU core, so I assume it is trying to run > > DEFLATE then somehow failing to compress at all? > > > > Looking at gdal_merge.py I think the major performance issue is the order > > in which it copies the data. Currently it copies an entire image at a > > time (1 colour channel at a time). Thus DEFLATE will not work due to the > > rather random write pattern to each scanline. > > > > I think a much faster method would be to calculate the destination > > rectangles for each file into some sort of list. Aftter this generate the > > destination file 1 scanline at a time, calculating which source images > > intersect, and working left to right filling with solid color or copying > > scanlines from the source image. > > > > This allows the DEFLATE to work far more effciently as the write pattern > > is horizontally linear. > > > > What are your views/suggestions/etc.? > > > > Thanks, > > Leith Bade > > [email protected] > > > > _______________________________________________ > > > > gdal-dev mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > > > > _______________________________________________ > > gdal-dev mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
