
NAMEzgtcon.f SYNOPSISFunctions/Subroutinessubroutine zgtcon (NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, INFO) Function/Subroutine Documentationsubroutine zgtcon (characterNORM, integerN, complex*16, dimension( * )DL, complex*16, dimension( * )D, complex*16, dimension( * )DU, complex*16, dimension( * )DU2, integer, dimension( * )IPIV, double precisionANORM, double precisionRCOND, complex*16, dimension( * )WORK, integerINFO)ZGTCON Purpose:ZGTCON estimates the reciprocal of the condition number of a complex tridiagonal matrix A using the LU factorization as computed by ZGTTRF. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))). NORM
Author:
NORM is CHARACTER*1 Specifies whether the 1norm condition number or the infinitynorm condition number is required: = '1' or 'O': 1norm; = 'I': Infinitynorm.N N is INTEGER The order of the matrix A. N >= 0.DL DL is COMPLEX*16 array, dimension (N1) The (n1) multipliers that define the matrix L from the LU factorization of A as computed by ZGTTRF.D D is COMPLEX*16 array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A.DU DU is COMPLEX*16 array, dimension (N1) The (n1) elements of the first superdiagonal of U.DU2 DU2 is COMPLEX*16 array, dimension (N2) The (n2) elements of the second superdiagonal of U.IPIV IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.ANORM ANORM is DOUBLE PRECISION If NORM = '1' or 'O', the 1norm of the original matrix A. If NORM = 'I', the infinitynorm of the original matrix A.RCOND RCOND is DOUBLE PRECISION The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1norm of inv(A) computed in this routine.WORK WORK is COMPLEX*16 array, dimension (2*N)INFO INFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Definition at line 141 of file zgtcon.f.
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