linear system problem
Thu Jan 29 15:14:00 GMT 2004

Dear sirs, 
I am a student of Computer Engineering at Madrid
University, Spain.
First of all I want to congratulate you for the
very useful "Scientific Library GSL" you have.
The matter that concerns me is:

I need to solve the linear system A x = b, where A
is a rectangular M-by-N matrix, and M > N. Looking the
functions of the library, I decided to use de QR descomposition. 
Before any calculation, I create the A matrix and b vector view, the 'x' 
and 'tau' vectors of N size, and the 'residual' vector of M size.
 First, I call the function gsl_linalg_QR_decomp() with the matrix A and 
the vector 'tau'. Then I call the gsl_linalg_QR_lssolve() function with 
the arguments A (with the QR descomposition created by the previous 
function), tau, b, x, and residual, to find the solution to the linear 
 I´m almost sure that these equations are correct but
 the solution is not. 
 What should I expect ? 
 My question is; am I either using the right functions, or puting them in 
the right order? 
 Shall I use another kind of descomposition?
   Thank you very much for your cooperation 
   Jaime Carsi Jaudenes.

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