[gdal-dev] Re: Weird gdal2tiles performance inconsistency

[mladen-g at distributel.net]

Hi Vadim,

Just wanted to say thanks for suggesting the tilers-tools package.   
Over the past few weeks I've done some testing with it, and while it  
has some minor quirks, I think it's overall a better solution for me.

I do still see the strange performance drop in low zoomlevels, but  
since performance is overall much better, it's easier to tolerate.

I see on the Google code site that you're the project owner, so good job!

Regards,
Mladen

Quoting vadp.devl at gmail.com:

> Hi Mladen,
>
> On Fri, Dec 23, 2011 at 3:58 AM,  <mladen-g at distributel.net> wrote:
> > This takes about 16 seconds on my machine.
> >
> ...
> > This takes 32 seconds, or about double the time of tiling zoomlevels 1-7.
>
> Not really an answer to your question, but if you are about a timinig
> issues for you rater processing you may give a try to gdal_tiler.py
> from http://code.google.com/p/tilers-tools.
>
> Regards
> Vadim


Quoting mladen-g at distributel.net:

> Hi all,
>
> I'm seeing some very strange performance from gdal2tiles on a  
> particular grid, so I'm wondering if someone has an insight into why  
> this is happening.
>
> The problem is that when I tile the grid at zoom level 7, I get much  
> better performance than with other zoomlevels, including lower ones  
> (!).
>
> The grid is this (zipped PNG, ~2.7Mb):
> http://dl.dropbox.com/u/53500018/ontarioOrigSizeTrimReprojected.zip
>
> So, let's say I run this command:
> gdal2tiles.bat -w google -s EPSG:4326 -z 1-7 -v  
> C:\temp\ontarioOrigSizeTrimReprojected.png
> C:\temp\outputTiles
>
> This takes about 16 seconds on my machine.
>
> But if I replace the last line to be zoom level 1:
> gdal2tiles.bat -w google -s EPSG:4326 -z 1-1 -v  
> C:\temp\ontarioOrigSizeTrimReprojected.png
> C:\temp\outputTiles
>
> This takes 32 seconds, or about double the time of tiling zoomlevels  
> 1-7.  Note also that I've experimented with other maximum zoomlevels  
> (5,6,8,9,10,11) and they all run slower than 7.
>
> So, does anyone know Why does this strange behaviour happen on zoom  
> level 7?  And is there any way to optimize the input to gdal2tiles  
> for better performance?
>
> Regards,
> Mladen
>
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