[mkgmap-dev] max-jobs patch

Mon Feb 5 12:10:46 GMT 2018

Hi Gerd,
I think it's even more in combination with DEM. I usually use 6 of my 8
cores and ending up with 10 to 12 GB of heap. So I definitely agree with
you available heap somehow needs to be considered as well. Not only CPU
cores. Btw. for CFD/FEM analysis the simulation is usually is faster if
you only use physical cores, not the 'virtual' ones. Don't know how
mkgmap will behave.

Henning

On 05.02.2018 15:28, Gerd Petermann wrote:
> Hi Mike,
>
> thought about this again. Maybe this change is too simple. With multiple jobs one also
> needs more heap (-Xmx JRE option). If you create rather large tiles with splitter (max-nodes=1600000)
> you need 0.5 - 1 GB for each job. Not sure what happens when a user creates a map with
> 10 tiles on an 8-core machine without any -Xmx option.
>
> I fear this will result in OutOfMemory exception, so better check the available heap as well.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Sonntag, 4. Februar 2018 15:14
> An: 'Development list for mkgmap'
> Betreff: [mkgmap-dev] max-jobs patch
>
> Hi Gerd,
>
> Please find attached a patch that amends the default behaviour if the
> --max-jobs option is not specified, to using a value equal to the number of
> CPU cores, as suggested in a previous post. The documentation is also
> amended to reflect the change. This halves the execution time of mkgmap for
> building a map of Staffordshire on my 8-core PC when --max-jobs is not
> specified (I didn't know about this option previously and was unaware the
> performance could have been improved).
>
> Cheers,
> Mike
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