larrr(3) LAPACK larrr(3)
NAME
larrr - larrr: step in stemr, test to do expensive tridiag eig algorithm
SYNOPSIS
Functions
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.
Detailed Description
Function Documentation
subroutine dlarrr (integer n, double precision, dimension( * ) d, double
precision, dimension( * ) e, integer info)
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
subroutine slarrr (integer n, real, dimension( * ) d, real, dimension( * )
e, integer info)
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
Author
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