[Tilesathome] Patch for Tiles at home running with two processes

[Dirk-Lüder Kreie]

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Jocelyn Jaubert schrieb:
> Hi,
> 
> I have just made a patch so that tilesGen.pl forks in RenderTile
> function (which generates png from svg). It is quite simple, as it
> calls fork() at the first run of RenderTile. Parent and child then just
> draw a different part of the tile.
> 
> I originally wanted to make it multi-thread, but it segfaulted in the
> for loop line 1237, but I didn't investigate any more. (it could be a
> problem in how GD library is used).
> 
> Patch contains the following modifications:
> 
>  * make temporary files safer, by using tempfile() to generate unique
> file names.
>  * addition of $parent_pid so that the child can get the name of the
> output-* files used by xml2svg(). This could be replaced by using
> coordinates of the tile in file name.
>  * a new configuration in tilesAtHome.conf to enable or deactivate
> fork().
> 
> I measured time on a very simple tile (2129,1489) which contains only a
> road. Total time went from 2:30 to 1:30 on my dual core.
> 
> 
> The patch can be easily be modified to use 3 children instead of only 1,
> and I think that xml2svg could use some fork() too.

The patch is in svn (with minor modifications) Fork=X results in 2^X
processes, so Fork=0 is the old behavior, while any positive non-zero
integer value makes multiple processes run in parallel.

Doesn't seem to work on Windows (Vista?). Needs more testing on Windows
multicore/-cpu PCs.


- --

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

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