Changes between Version 62 and Version 63 of Grass7/RasterLib

Timestamp:

Jun 30, 2011, 11:01:57 AM (13 years ago)

Author:

huhabla

Comment:

--

Grass7/RasterLib

@@ -38 +38 @@
  * Storage in '''tiles''' instead of by row
   * Reasoning: Glynn said on the mailing list: "In most cases, single-level tiled storage will give you close to the same performance with a lot less complexity."
+    * The G3d library already implements a tile based approach with tile caching and tile file buffer for arbitrary read and write access
   * Function needed to check whether tiles are all null, or all the same value.
   * What tile size should be used? Could be user/program specified, or standard value of something like 64x64. If there isn't a fixed value then there should be utility program that can convert tiled rasters to different tile sizes.
+    * The tile size in the G3d library is variable and can be set when a new map is created. The program r3.retile can be used to store raster3d maps with different tile size. Additionally a function is implemented to compute the optimal tile dimension for a given max size in bytes.
   * However, row-oriented storage has the advantage that you can easily skip entire rows when downsampling. Using e.g. 64x1 "tiles" would provide both optimisations, but at the expense of reduced compression, as you need a pointer (8 bytes) for each tile, and the compression has to be restarted for each tile.
  * Merge NULL file into main data array.
+   * This approach is implemented in the G3d library
 
 === Directory structure ===