[vtkusers] Copying memory instead of resizing allocation in vtkDataArrayTemplate::Resize()

[Mathieu Malaterre]

Jens,

	Could you submit a feature request, in our bug tracker at:

	http://vtk.org/Bug

Thanks.
Mathieu

Jens wrote:
> Hi
> I would like to read grids with millions of cells and developed a reader for 
> my private netCDF file format.
> 
> I thought reading the file in chunks of 100000 cells. That for I create a 
> vtkDoubleArray to add all nodes of the 100000 cells and resize that 
> vtkDoubleArray each time I read the next chunk of cells.
> 
> I had a look at the function resizing the vtkDoubleArray because I have to 
> make sure not to use more memory than needed. ( Its "Resize()" in 
> vtkCommon/vtkDataArrayTemplate.txx line 273 in Vtk-5-branch )
> 
> This function uses "memcpy" instead of "realloc" to resize the double array.
> ( http://www.codecogs.com/reference/stdlib.h/malloc.php?alias=realloc
> http://www.codecogs.com/reference/string.h/memcpy.php?alias=memcpy )
> 
> That means that each time Resize get used the data is twice in memory for a 
> short time. That´s slow and needs double memory.
> 
> What´s wrong with realloc ?
> 
> 		Greetings
> 			Jens
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