[Gdal-dev] Re: ECW compression - Extremely slow Linux performance - Re: ECW compression - Extremely slow Linux performance - POSSIBLE HACKISH SOLUTION (Andrew Larcombe

[John Johnson]

> Date: Mon, 21 Aug 2006 17:53:53 +0100
> From: Andrew Larcombe <andrew at andrewlarcombe.co.uk>
> Subject: Re: [Gdal-dev] ECW compression - Extremely slow Linux
>         performance     - POSSIBLE HACKISH SOLUTION
> To: gdal-dev at lists.maptools.org
> Message-ID: <44E9E521.7000304 at andrewlarcomb
> e.co.uk>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Initial testing appears to show that running ECW conversion from
> gdal_translate in FWTools under the windows non-emulator, WINE, is
> 6xfaster than running it natively. I'm now getting translation times of
> around 10 seconds, rather than 60 seconds on my laptop. I can only
> assume wine's multithreading is less crippled than that provided by
> ERMapper?
>
>
We moved to a WINE based solution for stability and found the same
performace gain.

In addition to being extremely slow in the Linux version, it's also quite
buggy. Apparently the ERMapper folks really don't understand the posix
threading model. We can limp along for a while in a single threaded app
before crashing. But calling any ECW decode routines from a multithreaded
app running on a multiprocessor machine (even if all the calls are made from
a single thread) causes all kinds of corruption of IO data structures and
crashes quite quickly. I haven't been able to get the ERMapper folks to be
any more specific than "Yes, we have some threading problems on Unix. We're
looking into it.".

Once we tried the WINE solution we also noticed the speedups.

Enjoy your WINE. :-)
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