Re: [gdal-dev] GDALWarp Datasets
Hello, Okay, all of that is well-taken. Thank you for your response. > If you're not interested in the pixel values, using GDALSuggestedWarpOutput2() is a better fit. Yes, my question was worded a bit unclearly: I am essentially interested in retrieving warped tiles so the pixels are of primary interest. Thank you, James McClain On Fri, Feb 15, 2019 at 4:58 AM Even Rouault wrote: > On vendredi 15 février 2019 00:06:28 CET James McClain wrote: > > Hello, > > > > If I may, I would like to a few questions regarding how best to use the > > GDALWarp function ( > > > https://github.com/OSGeo/gdal/blob/master/gdal/apps/gdalwarp_lib.cpp#L748-L7 > > 70) and the datasets that it creates. > > > > In particular, I am experimenting with using such datasets to read warped > > extents on an on-demand basis and in a thread-safe way. > > > > I have found that the VRT output format is lazy with respect to > computation > > and allocation which is great for my use case, but it appears not to be > > thread safe with respect to reading from a single warped dataset from > > multiple threads. > > No single GDALDataset object of any driver should be used simultaneously > by > multiple threads (this extends to any GDAL/OGR class instance). If this > seems > to work for GTiff, you're just lucky, but that might just fail as well. > If you need to access a dataset from several threads, each one should have > its > own GDALDataset object (so this won't work for the MEM driver) > > > > > On a more meta level, are datasets created by GDALWarp the right approach > > (if I want to lazy get warped extents in a thread-safe manner) or should > I > > look elsewhere? > > If you're not interested in the pixel values, using > GDALSuggestedWarpOutput2() > is a better fit. > > Even > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com > ___ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev -- "I prayed for freedom for twenty years, but received no answer until I prayed with my legs." -- Frederick Douglass ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] GDALWarp Datasets
On vendredi 15 février 2019 00:06:28 CET James McClain wrote: > Hello, > > If I may, I would like to a few questions regarding how best to use the > GDALWarp function ( > https://github.com/OSGeo/gdal/blob/master/gdal/apps/gdalwarp_lib.cpp#L748-L7 > 70) and the datasets that it creates. > > In particular, I am experimenting with using such datasets to read warped > extents on an on-demand basis and in a thread-safe way. > > I have found that the VRT output format is lazy with respect to computation > and allocation which is great for my use case, but it appears not to be > thread safe with respect to reading from a single warped dataset from > multiple threads. No single GDALDataset object of any driver should be used simultaneously by multiple threads (this extends to any GDAL/OGR class instance). If this seems to work for GTiff, you're just lucky, but that might just fail as well. If you need to access a dataset from several threads, each one should have its own GDALDataset object (so this won't work for the MEM driver) > > On a more meta level, are datasets created by GDALWarp the right approach > (if I want to lazy get warped extents in a thread-safe manner) or should I > look elsewhere? If you're not interested in the pixel values, using GDALSuggestedWarpOutput2() is a better fit. Even -- Spatialys - Geospatial professional services http://www.spatialys.com ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] GDALWarp Datasets
Hello, If I may, I would like to a few questions regarding how best to use the GDALWarp function ( https://github.com/OSGeo/gdal/blob/master/gdal/apps/gdalwarp_lib.cpp#L748-L770) and the datasets that it creates. In particular, I am experimenting with using such datasets to read warped extents on an on-demand basis and in a thread-safe way. I have found that the VRT output format is lazy with respect to computation and allocation which is great for my use case, but it appears not to be thread safe with respect to reading from a single warped dataset from multiple threads. I have found that the MEM output format is safe with respect to concurrent reads, but is eager in its allocation and computation. I have found that the GTIFF output format is also safe with respect to concurrent reads (but CPU utilization is low so it looks like there is internal locking), and it is once again eager with respect to allocation and computation. What I would like to find is way to create a dataset that is both lazy and safe with respect to concurrent reads. Can anyone share any suggestions with me? (Note: the foregoing statements are based on experiments that I have done, not based on looking at the code; if any of the above is incorrect I am very happy to be corrected.) On a more meta level, are datasets created by GDALWarp the right approach (if I want to lazy get warped extents in a thread-safe manner) or should I look elsewhere? Thank you, James McClain -- "I prayed for freedom for twenty years, but received no answer until I prayed with my legs." -- Frederick Douglass ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
