[mkgmap-dev] Precompiled boundary files in one zip file

Sun Feb 12 21:12:27 GMT 2012

> Hi WanMil,
>
> I am still busy rewriting all the boundary code to allow reading bnd data
> from zip.
> Most of it is done, and I also found a few errors contained in my patch
> boundary_prep_quadtree_v2.patch

Great!!

>
> I have now a version that can read old bnd format, new quadtree bnd file
> format,
> both from zip or normal directory, and its BoundaryQuadtree delivers the
> same results as the
> version in the performance branch.

Great!!

> I did not see a big difference between reading from zip or directory, I
> think that is okay.

I expected an improvement when using more threads because then reading 
from disk is often a bottleneck. But obviously this is different between 
systems.

> I did not see any multi-threading problems while reading from zip, so I did
> not code anything
> special for this. You mentioned such problems, did you mean updating zip
> files?

I remember that I read warnings that the Java zip file implementation is 
not multithread capable. I'll have to search for them and will let you 
know if I find them.

>
> I don't think that we need a routine to write / create zip files, do we?

There will be one real improvement: The LocationHook first checks if the 
bounds directory contains bounds file. The time checking that has been 
improved much by your patch. But I still see quite high timings when 
using multiple threads. If using a zip file this timing should be much 
better because one just have to check if the on zip file is there.

A 2nd thing is that it is much easier to handle for users. That's what 
Klaus alias toc-rox metioned.

So decide yourself. I would vote for using zip files (and it would also 
be ok for me to drop the support for non zip files).

> I think we need a utility similar to BoundaryMerger to allow creating the
> bnd files for planet in multiple steps, so that's what I am working on now.

Yes. Otherwise it is not possible to create boundaries for larger 
regions if your computer does not have tons of GB.

WanMil

>
>
> Gerd
>
>
>
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