[gdal-dev] How to free memory allocated by ReadRaster, Python API

[Even Rouault]

Le Wednesday 08 April 2009 23:31:59 Ivan Lucena, vous avez écrit :
> Hi Even,
>
> D'accord. Good tip.
>
> Although I am planning to read a relative large number of bands (temporal
> series) I can probably enlarge my query windows and balance the memory load
> that it will take. I would do that if I was developing some kind of
> application. The thing is that Python + GDAL + numpy is a wonderful data
> exploration lab and that is all that I am doing in that case.
>
> But about your previous reply, I am far from that machine now but I am
> almost sure that am using the latest 'and greatest' trunk code. But I
> probably should run the setup.py again and re-install the extension, right?

Yes, you need to rebuild and install the bindings. In that instance, the leak 
was in them, not in the core GDAL library.

>
> My best regards,
>
> Ivan
>
> Even Rouault wrote:
> > And I forgot to mention that if you need to operate on big images, you'll
> > have probably suboptimal/poor performance by just extracting one pixel at
> > a time, as there's a non neglectable overhead for each binding function
> > call, especially that one. I'd advise you to read bigger chunks at once,
> > and then iterate on the result buffer.
> >
> > Le Wednesday 08 April 2009 21:16:18 Lucena, Ivan, vous avez écrit :
> >> Hi,
> >>
> >> I have a small Python script that uses ReadRaster to collect some values
> >> in order to do some math.
> >>
> >> The problem is that once I run the script through a Python IDE I can see
> >> the memory usage increasing but it does not decrease at the end.
> >>
> >> After some runs I got a out of memory crash on the IDE itself
> >> (PythonWin).
> >>
> >> My code is something like that:
> >>
> >> {{{
> >>
> >> for b in range(nbands):
> >>   for yoff in range(ysize):
> >>     for xoff in range(xsize):
> >>       buffer =
> >> ds.ReadRaster(xoff,yoff,1,1,1,1,datatype,range(1,1+nbands) #
> >>       # formulas and numpy calls
> >>       #
> >>       buffer = None
> >>
> >> ds = None
> >>
> >> }}}
> >>
> >> I am running with all my formulas commented just to isolate the memory
> >> problem. It just reads and does nothing.
> >>
> >> Does anybody has any advise on how to free that buffer?
> >>
> >> Thanks in advance,
> >>
> >> Regards,
> >>
> >> Ivan
> >>
> >>
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