[mkgmap-dev] [PATCH V1] Idea for minor speed improvement for boundary preprocessing

Fri Mar 2 15:34:07 GMT 2012

Hi Gerd,

that's great!

> Hi WanMil,
>
> this was a very good hint :-)
>
> Time for african boundaries was 250 secs with /branch/performance/r2225, 267
> secs with trunk,
> and with this patch it is now 152 secs

wow, that's more improvement than I expected.

>
> - use simple quadtree in BoundarySaver.splitArea()

You are a quadtree guy.
In this case I thinks it's more irritating and complex to split the area 
into four subareas. I've changed that to split into two subareas and the 
code is now much easier to read (I think so..?!?) and performs in 
similar speed.

WanMil

> - add try/catch in BoundaryPreparer.run() to allow e.g. usage of assert.
> Without that,
> an assertion was handled by the threading routines and caused program stop
> without any
> message.
>
> Please double check this, I am still not so experienced
> with try+catch and wrong placed
>
> Ciao,
> Gerd
>
> http://gis.19327.n5.nabble.com/file/n5512906/splitArea_v1.patch
> splitArea_v1.patch
>
>
> WanMil wrote
>>
>> Hi Gerd,
>>
>> boundary preprocessing takes quite a lot of time. That's not a big
>> problem because it's performed only by some people who publish their
>> results.
>>
>> But I think some speed improvements would not be bad anyhow?!
>>
>> While preprocessing asia and america I go an idea. The area of a
>> boundary is splitted into the raster. But each time the complete area is
>> intersected to the raster. In case an area is big and/or complex
>> (boundary of russia, USA, canada etc.) this takes a long time. It would
>> be possible first to cut the area into smaller pieces (columns or rows
>> of the raster) and then do the final cut to the raster. Maybe this saves
>> time because the column or row areas should be less complex.
>>
>> What do you think?
>>
>> WanMil
>> _______________________________________________
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>> mkgmap-dev at .org
>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>>
>
>
> --
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