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[mkgmap-dev] max-jobs patch

From Gerd Petermann gpetermann_muenchen at hotmail.com on Mon Feb 5 07:28:01 GMT 2018

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.


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).


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