1lis_array_qr(3)              Lis Library Functions             lis_array_qr(3)
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NAME

6       lis_array_qr - calculate the eigenvalues with the QR algorithm
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SYNOPSIS

10       #include "lis.h"
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12       LIS_INT   lis_array_qr(LIS_INT   n,  LIS_SCALAR  a[],  LIS_SCALAR  q[],
13       LIS_SCALAR r[], LIS_INT *qriter, LIS_SCALAR *qrerr);
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DESCRIPTION

17       Calculate the eigenvalues of matrix A with the QR algorithm.
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INPUT

21       n      The size of the matrices
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24       a      The array that stores matrix A of size n * n
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27       q      The work array Q of size n * n
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30       r      The work array R of size n * n
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OUTPUT

34       a      The array that stores the block upper-triangular matrix with ei‐
35              genvalues in the block diagonal elements after similarity trans‐
36              formation
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39       qriter The number of iterations of the QR algorithm
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42       qrerr  The 2-norm of the first subdiagonal element A(2,1)  after  simi‐
43              larity transformation
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EXIT STATUS

47       The following exit values are returned:
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49       0      The process is normally terminated
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51       unspecified
52              An error occurred
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SEE ALSO

56       lis(3)
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58       http://www.ssisc.org/lis/
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63Man Page                          1 Nov 2014                   lis_array_qr(3)