[vtkusers] Memory allocation problems under Python wrapped VTK in Windows

[Lassi Paavolainen]

On Fri, 16 Jan 2009, Berk Geveci wrote:

> How are you testing the memory allocation from Python?
> 
> -berk

I just created a really simple VTK class which included that test code 
inside one method. Then I compiled and made a wrapper to Python for that 
class. Then just executed that method from Python interpreter.

Lassi

> On Fri, Jan 16, 2009 at 4:02 AM, Lassi Paavolainen <lopaavol at jyu.fi> wrote:
> > Hi,
> >
> > I was wondering about a memory allocation problem that seems to be only in
> > some machines where we run our software so I decided to make a simple test
> > program for that (code attached at the end of the message).
> >
> > I got some interesting results from the test program that I cannot
> > explain. I used same code in console application not using VTK and in VTK
> > class but got different results of maximum memory possible to dynamically
> > allocate. Result was also platform dependent in VTK class.
> >
> > To the results. I used three different systems explained below:
> >
> > Linux (64 bit): 2 GB of RAM, VTK 5.2, Python 2.5
> > Windows Vista (32 bit): 3 GB of RAM, VTK 5.2, Python 2.6
> > Windows XP Pro (32 bit): 8 GB of RAM (3 GB usable), VTK 5.2, Python 2.6
> >
> > Exactly same code was used in both Windows machines (compiled in Vista). I
> > ran this code from command line and using Python interpreter to ran
> > wrapped VTK class and got following interesting results:
> >
> > Linux:
> > - bash: about 3300 MB
> > - Python: about 3300 MB
> >
> > Vista:
> > - Command line: about 1720 MB
> > - Python: about 1180 MB!!!
> >
> > XP Pro:
> > - Command line: about 1920 MB
> > - Python: about 720 MB!!!
> >
> > So my question is, how it is possible that VTK class ran from Python in
> > Windows can't allocate as much continuous memory as it is possible to
> > simple application? Same thing happens if I try to allocate memory using
> > for example vtkUnsignedCharArray. I'm guessing the problem is not in VTK
> > but Python wrapped VTK. Does anyone know where that memory limit defined
> > by Python wrapped VTK and platform is coming from?
> >
> > Here is the memory allocation testing code. Probably not the best but
> > gives similar results as in real application.
> >
> > #include <iostream>
> >
> > #define START_ALLOC 1048576
> > #define MAX_ALLOC 4294967296
> > #define START_STEP 536870912
> >
> > int main(int argc, char* argv[])
> > {
> >  long long alloc = START_ALLOC;
> >  long long maxAlloc = MAX_ALLOC;
> >  long long minAlloc = 0;
> >  long long step = START_STEP;
> >  while(maxAlloc - minAlloc > START_ALLOC)
> >    {
> >    std::cout << "Allocating " << alloc << " bytes of memory." << std::endl;
> >    try
> >      {
> >      char *mem = new char[alloc];
> >      minAlloc = alloc;
> >      alloc += step;
> >      delete[] mem;
> >      }
> >    catch (std::bad_alloc &ba)
> >      {
> >      std::cout << "Couldn't allocate " << alloc / 1048576 << " MB of memory." << std::endl;
> >      maxAlloc = alloc;
> >      alloc = minAlloc;
> >      step /= 2;
> >      alloc += step;
> >      }
> >    }
> >
> >  std::cout << "Maximum size of memory allocated: " << minAlloc / 1048576 << " MB" << std::endl;
> >
> >  return 0;
> > }
> >
> > Regards,
> > Lassi Paavolainen
> > _______________________________________________
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> 

-- 
Lassi Paavolainen, M.Sc.
Software Engineer
BioImageXD (http://www.bioimagexd.net)
lopaavol at jyu.fi