sptcon.f man page
subroutine sptcon (N, D, E, ANORM, RCOND, WORK, INFO)
subroutine sptcon (integerN, real, dimension( * )D, real, dimension( * )E, realANORM, realRCOND, real, dimension( * )WORK, integerINFO)
SPTCON 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))).
N is INTEGER The order of the matrix A. N >= 0.
D is REAL array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization of A, as computed by SPTTRF.
E is REAL array, dimension (N-1) The (n-1) off-diagonal elements of the unit bidiagonal factor U or L from the factorization of A, as computed by SPTTRF.
ANORM is REAL The 1-norm of the original matrix A.
RCOND is REAL 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.
WORK is REAL array, dimension (N)
INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
The method used is described in Nicholas J. Higham, "Efficient Algorithms for Computing the Condition Number of a Tridiagonal Matrix", SIAM J. Sci. Stat. Comput., Vol. 7, No. 1, January 1986.
Definition at line 119 of file sptcon.f.
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sptcon(3) is an alias of sptcon.f(3).