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larrr(3) LAPACK larrr(3)

larrr - larrr: step in stemr, test to do expensive tridiag eig algorithm


subroutine dlarrr (n, d, e, info)
DLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues. subroutine slarrr (n, d, e, info)
SLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

DLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Purpose:



 Perform tests to decide whether the symmetric tridiagonal matrix T


 warrants expensive computations which guarantee high relative accuracy


 in the eigenvalues.

Parameters

N 



          N is INTEGER


          The order of the matrix. N > 0.

D



          D is DOUBLE PRECISION array, dimension (N)


          The N diagonal elements of the tridiagonal matrix T.

E



          E is DOUBLE PRECISION array, dimension (N)


          On entry, the first (N-1) entries contain the subdiagonal


          elements of the tridiagonal matrix T; E(N) is set to ZERO.

INFO



          INFO is INTEGER


          INFO = 0(default) : the matrix warrants computations preserving


                              relative accuracy.


          INFO = 1          : the matrix warrants computations guaranteeing


                              only absolute accuracy.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA

SLARRR performs tests to decide whether the symmetric tridiagonal matrix T warrants expensive computations which guarantee high relative accuracy in the eigenvalues.

Purpose:



 Perform tests to decide whether the symmetric tridiagonal matrix T


 warrants expensive computations which guarantee high relative accuracy


 in the eigenvalues.

Parameters

N 



          N is INTEGER


          The order of the matrix. N > 0.

D



          D is REAL array, dimension (N)


          The N diagonal elements of the tridiagonal matrix T.

E



          E is REAL array, dimension (N)


          On entry, the first (N-1) entries contain the subdiagonal


          elements of the tridiagonal matrix T; E(N) is set to ZERO.

INFO



          INFO is INTEGER


          INFO = 0(default) : the matrix warrants computations preserving


                              relative accuracy.


          INFO = 1          : the matrix warrants computations guaranteeing


                              only absolute accuracy.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

Beresford Parlett, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA

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