[Insight-users] question about vnl_cholesky

[zhuang song]

Hi all,
I use vnl_cholesky to solve a symmetric matrix. sometimes it returns an 
error message like:
vnl_cholesky: 1 dimensions of non-posdeffness.  what does it mean? does 
it indicate the matrix is
 not symmetric?

is there any matrix size limitation when applying vnl_cholesky?

thanks,
Zhuang

insight-users-request at itk . org wrote:

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>Today's Topics:
>
>   1. ImageSource->GetOutput() type (Benjamin King)
>   2. Question about itkDICOMImageSeriesTest (jiang)
>
>--__--__--
>
>Message: 1
>To: ITK <insight-users at itk . org>,
>	Bill Hoffman <bill . hoffman at kitware . com>
>From: Benjamin King <king . benjamin at mh-hannover . de>
>Organization: mhh
>Date: Thu, 28 Aug 2003 10:50:36 +0100
>Subject: [Insight-users] ImageSource->GetOutput() type
>
>------------065IJz5Pgc4QrUW4IYQgb8
>Content-Type: text/plain; charset=iso-8859-15; format=flowed
>
>Hi all,
>
>I want to wrap a part of my pipeline in a function, but I'm troubled by the 
>difference between itk::Image::Pointer and itk::Image*.
>My function looks like (also see the attached code):
>
>  ImageType::Pointer someFunction(ImageType* image);
>
>I chose the argument's type like that because according to the
>documentation all itk::ImageSources return a plain pointer with
>GetOutput(). The return value's type is used in accordance to a previous 
>post by Bill (http://www . itk . org/pipermail/insight-users/2003- 
>June/004124.html).
>
>When I run the attached code, the image returned by someFunction
>is an empty image, even after I Update()d it.
>
>In a related context, I have functions like
>  double returnSomeFeature(ImageType* image);
>that work fine for filter outputs but not for "handcrafted" images:
>  // Compiles
>  double feature1 = returnSomeFeature(imageReader->GetOutput);
>
>  // Doesn't compile
>  ImageType::Pointer image = ImageType::New();
>  image->SetLargetsPossibleRegion(....)
>  image->SetBufferedRegion(....)
>  image->Allocate(....)
>  double feature2 = returnSomeFeature(image);
>The attached code doesn't demonstrate this, but I guess the problems
>are related in some way.
>
>Can someone point out the problem or reproduce the error?
>
>
>Best regards,
>  Benjamin
>
>  
>