[GRASS-dev] [GRASS GIS] #2750: LZ4 when writing raster rows; better than double I/O bound r.mapcalc speed

[GRASS GIS]

#2750: LZ4 when writing raster rows; better than double I/O bound r.mapcalc speed
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  Reporter:  sprice       |      Owner:  grass-dev@…
      Type:  enhancement  |     Status:  new
  Priority:  normal       |  Milestone:  7.1.0
 Component:  Raster       |    Version:  svn-trunk
Resolution:               |   Keywords:  ZLIB LZ4 ZSTD
       CPU:  OSX/Intel    |   Platform:  MacOSX
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Comment (by mmetz):

 Replying to [comment:33 neteler]:
 > Replying to [comment:32 sprice]:
 > > Hey all, just checking in. What is remaining to get this pushed to the
 GRASS v7.1 code?
 >
 >
 > For me two things are yet open.
 >
 > First:
 >
 > Replying to [comment:30 neteler]:
 > > "User" comment: I would suggest to always activate the NULL file
 compression by default, anything else would be confusing.
 >
 > --> not yet reflected in the patch (so, the meaning of the var
 `GRASS_COMPRESS_NULLS` should be inverted or, better, implemented as
 `GRASS_NOCOMPRESS_NULLS=1`. I have terabytes of uncompressed NULL files at
 time and would like to get rid of wasting too much disk space.

 That concerns #2349.
 >
 > Second:
 >
 > We need a patch for GRASS GIS 7.0 for backward compatibility, at least
 for the NULL file compression. Which leads to the suggestion that either
 RLE or BZIP should be used here since these two compressors are already
 present in releasebranch70.

 No, neither the generic RLE algorithm nor BZIP support is available in
 relbr70. Note that CELL RLE compression is rasterlib-internal and tailored
 for integer numbers with variable byte size. Therefore it does not make
 sense to use the rasterlib-internal RLE method to compress null files
 where the informative unit is one bit, not 1-4 bytes. For relbr70, null
 files could be (un-)compressed with ZLIB's DEFLATE, other methods would
 not be supported.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2750#comment:36>
GRASS GIS <https://grass.osgeo.org>