On Wed, Dec 6, 2017 at 10:41 AM, Markus Neteler <[email protected]> wrote: > [...] > > # null file > identical > > Curiosity: would it makes sense to compress the "nullcmpr" file according to the selected compression? Probably Markus M had already explained it but I don't remember...
In short, it's a waste of time. Null files are very small with one bit per cell. Small data are difficult to compress, and using a stronger compression method might actually produce a larger, not a smaller output, and it takes longer. Regarding null file compression, LZ4 is not only the fastest method, it is also regularly the method with the best compression ratio. Null files and [f]cell files have different characteristics regarding compression, therefore one compression method can perform best for cell values and another one might perform best for null file compression. You would need to be able to choose separate compressors for the actual data and the null file in order to achieve maximum compression or the best compromise between speed and compression. That's too complicated. Most of the time LZ4 is a good if not the best choice, therefore null file compression is fixed to LZ4. Markus M > > Best, > markusN > > -- > Markus Neteler, PhD > http://www.mundialis.de - free data with free software > http://grass.osgeo.org > http://courses.neteler.org/blog > > > _______________________________________________ > grass-dev mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/grass-dev
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