[vtkusers] AllocateOutputData of vtkImageSource

[Leila Baghdadi]

Hi everyone

I am writing a reader for my file format and I have vtkImageReader2 as its 
parent.

In my own reader at ExecuteData I have
vtkImageData *data = this->AllocateOutputData(output);

and I noticed that calling AllocateOutputData will result in 
ExecuteInformation to be called twice,

so I have checked vtkImageSource and I see there is a message there saying
that
this->ExecuteInformation() should be eliminated but nevertheless 

it is there for the time being

so my question is

what kind of inefficiency are we talking about when the
ExecuteInformation of my own reader is called twice.


Thanks


Leila