[Lapack] Regarding functions and results from CLAPACK
Date: Mon, 28 Aug 2006 16:24:03 -0400
I am Koushik Aravalli from Clemson University. I am using CLAPACK for my
research and trying to decode the resultant matrices formed from the
subroutines dgeqr2.c, dgetrf.c. For example the final matrix formed out from
the dgetrf subroutine is a combination of a matrix produced from a scalar
and a vector. The below message is from the subroutine mentioned.
FROM CLAPACK dgetrf subroutine.
The matrix Q is represented as a product of elementary reflectors
Q = H(1) H(2) . . . H(k), where k = min(m,n).
Each H(i) has the form
H(i) = I - tau * v * v'
where tau is a real scalar, and v is a real vector with
v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i),
and tau in TAU(i).
So if I solve for a linear equation set using QR decomposition, the final
matrix obtained is a product of reflectors. Comparing with the MATLAB
results I am not able to figure out a way to decode the matrix obtained from
"dgetrf" subroutine. By the way I am using MS Visual studio to do these
Can you please help me out in obtaining the decoded matrix results.
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