dptcon
dptcon - compute the reciprocal of the condition number (in the 1-norm) of a real symmetric positive definite tridiagonal matrix using the factorization A = L*D*L**T or A = U**T*D*U computed by SPTTRF
SUBROUTINE DPTCON( N, DIAG, OFFD, ANORM, RCOND, WORK, INFO)
INTEGER N, INFO
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION DIAG(*), OFFD(*), WORK(*)
SUBROUTINE DPTCON_64( N, DIAG, OFFD, ANORM, RCOND, WORK, INFO)
INTEGER*8 N, INFO
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION DIAG(*), OFFD(*), WORK(*)
SUBROUTINE PTCON( [N], DIAG, OFFD, ANORM, RCOND, [WORK], [INFO])
INTEGER :: N, INFO
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: DIAG, OFFD, WORK
SUBROUTINE PTCON_64( [N], DIAG, OFFD, ANORM, RCOND, [WORK], [INFO])
INTEGER(8) :: N, INFO
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: DIAG, OFFD, WORK
#include <sunperf.h>
void dptcon(int n, double *diag, double *offd, double anorm, double *rcond, int *info);
void dptcon_64(long n, double *diag, double *offd, double anorm, double *rcond, long *info);
dptcon computes the reciprocal of the condition number (in the
1-norm) of a real symmetric positive definite tridiagonal matrix
using the factorization A = L*D*L**T or A = U**T*D*U computed by
SPTTRF.
Norm(inv(A)) is computed by a direct method, and the reciprocal of
the condition number is computed as
RCOND = 1 / (ANORM * norm(inv(A))).
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* N (input)
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The order of the matrix A. N >= 0.
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* DIAG (input)
-
The n diagonal elements of the diagonal matrix DIAG from the
factorization of A, as computed by SPTTRF.
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* OFFD (input)
-
The (n-1) off-diagonal elements of the unit bidiagonal factor
U or L from the factorization of A, as computed by SPTTRF.
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* ANORM (input)
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The 1-norm of the original matrix A.
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* RCOND (output)
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The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is the
1-norm of inv(A) computed in this routine.
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* WORK (workspace)
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dimension(N)
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* INFO (output)
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