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[Lapack] issues with wrong result..


I guess you get the result from applying directly DGETRI on A ...

Well no, this does not work like this, to compute the inverse of A with 
DGETRI, you first need to call DGETRF then DGETRI as explained in the 
header of the routine:

*  DGETRI computes the inverse of a matrix using the LU factorization
*  computed by DGETRF.

Your code should not be muche more harder. Just insert a call to DGETRF 
before the call to DGETRI and it should a priori work.

Julien.

For the LAPACKers, try:
        A = [ 1 0.5 0.25 ; 0.5 1 0.5 ;  0.25 0.5 1];
        U=triu(A);  L=tril(A,-1)+eye(3); inv(L*U)
:)

On Thu, 2 Aug 2007, sabhnani@Domain.Removed wrote:

Hi,

I downloaded clapack and trying to use dgetri and dpptri functions but am
getting wrong results for inverse of matrices.

Particularly,

[ 1 0.5 0.25 ]               [ 1.25 -0.5 0.0  ]
[ 0.5 1 0.5  ]    =====>     [ -0.5 1.25 -0.5 ]
[ 0.25 0.5 1 ]               [ 0.0 -0.5 1.25  ]

Do you know what might be the problem?

Thanks in advance for your time.
Robin

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