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---
:name: zgtcon
:md5sum: 27adfc903351ec100318405f24932950
:category: :subroutine
:arguments:
- norm:
:type: char
:intent: input
- n:
:type: integer
:intent: input
- dl:
:type: doublecomplex
:intent: input
:dims:
- n-1
- d:
:type: doublecomplex
:intent: input
:dims:
- n
- du:
:type: doublecomplex
:intent: input
:dims:
- n-1
- du2:
:type: doublecomplex
:intent: input
:dims:
- n-2
- ipiv:
:type: integer
:intent: input
:dims:
- n
- anorm:
:type: doublereal
:intent: input
- rcond:
:type: doublereal
:intent: output
- work:
:type: doublecomplex
:intent: workspace
:dims:
- 2*n
- info:
:type: integer
:intent: output
:substitutions: {}
:fortran_help: " SUBROUTINE ZGTCON( NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* ZGTCON estimates the reciprocal of the condition number of a complex\n\
* tridiagonal matrix A using the LU factorization as computed by\n\
* ZGTTRF.\n\
*\n\
* An estimate is obtained for norm(inv(A)), and the reciprocal of the\n\
* condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* NORM (input) CHARACTER*1\n\
* Specifies whether the 1-norm condition number or the\n\
* infinity-norm condition number is required:\n\
* = '1' or 'O': 1-norm;\n\
* = 'I': Infinity-norm.\n\
*\n\
* N (input) INTEGER\n\
* The order of the matrix A. N >= 0.\n\
*\n\
* DL (input) COMPLEX*16 array, dimension (N-1)\n\
* The (n-1) multipliers that define the matrix L from the\n\
* LU factorization of A as computed by ZGTTRF.\n\
*\n\
* D (input) COMPLEX*16 array, dimension (N)\n\
* The n diagonal elements of the upper triangular matrix U from\n\
* the LU factorization of A.\n\
*\n\
* DU (input) COMPLEX*16 array, dimension (N-1)\n\
* The (n-1) elements of the first superdiagonal of U.\n\
*\n\
* DU2 (input) COMPLEX*16 array, dimension (N-2)\n\
* The (n-2) elements of the second superdiagonal of U.\n\
*\n\
* IPIV (input) INTEGER array, dimension (N)\n\
* The pivot indices; for 1 <= i <= n, row i of the matrix was\n\
* interchanged with row IPIV(i). IPIV(i) will always be either\n\
* i or i+1; IPIV(i) = i indicates a row interchange was not\n\
* required.\n\
*\n\
* ANORM (input) DOUBLE PRECISION\n\
* If NORM = '1' or 'O', the 1-norm of the original matrix A.\n\
* If NORM = 'I', the infinity-norm of the original matrix A.\n\
*\n\
* RCOND (output) DOUBLE PRECISION\n\
* The reciprocal of the condition number of the matrix A,\n\
* computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an\n\
* estimate of the 1-norm of inv(A) computed in this routine.\n\
*\n\
* WORK (workspace) COMPLEX*16 array, dimension (2*N)\n\
*\n\
* INFO (output) INTEGER\n\
* = 0: successful exit\n\
* < 0: if INFO = -i, the i-th argument had an illegal value\n\
*\n\n\
* =====================================================================\n\
*\n"
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