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sgtcon (3)
  • >> sgtcon (3) ( Solaris man: Библиотечные вызовы )
  • 
    NAME
         sgtcon - estimate the reciprocal of the condition number  of
         a  real  tridiagonal  matrix A using the LU factorization as
         computed by SGTTRF
    
    SYNOPSIS
         SUBROUTINE SGTCON( NORM, N, DL, D,  DU,  DU2,  IPIV,  ANORM,
                   RCOND, WORK, IWORK, INFO )
    
         CHARACTER NORM
    
         INTEGER INFO, N
    
         REAL ANORM, RCOND
    
         INTEGER IPIV( * ), IWORK( * )
    
         REAL D( * ), DL( * ), DU( * ), DU2( * ), WORK( * )
    
    
    
         #include <sunperf.h>
    
         void sgtcon(char norm, int n, float  *dl,  float  *d,  float
                   *du,  float  *du2, int *ipivot, float anorm, float
                   *srcond, int *info) ;
    
    PURPOSE
         SGTCON estimates the reciprocal of the condition number of a
         real tridiagonal matrix A using the LU factorization as com-
         puted by SGTTRF.
    
         An estimate is obtained for norm(inv(A)), and the reciprocal
         of  the condition number is computed as RCOND = 1 / (ANORM *
         norm(inv(A))).
    
    
    ARGUMENTS
         NORM      (input) CHARACTER*1
                   Specifies whether the 1-norm condition  number  or
                   the infinity-norm condition number is required:
                   = '1' or 'O':  1-norm;
                   = 'I':         Infinity-norm.
    
         N         (input) INTEGER
                   The order of the matrix A.  N >= 0.
    
         DL        (input) REAL array, dimension (N-1)
                   The (n-1) multipliers that  define  the  matrix  L
                   from  the  LU  factorization  of  A as computed by
                   SGTTRF.
    
         D         (input) REAL array, dimension (N)
                   The n diagonal elements of  the  upper  triangular
                   matrix U from the LU factorization of A.
    
         DU        (input) REAL array, dimension (N-1)
                   The (n-1) elements of the first  superdiagonal  of
                   U.
    
         DU2       (input) REAL array, dimension (N-2)
                   The (n-2) elements of the second superdiagonal  of
                   U.
    
         IPIV      (input) 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  indi-
                   cates a row interchange was not required.
    
         ANORM     (input) REAL
                   If NORM = '1' or 'O', the 1-norm of  the  original
                   matrix A.  If NORM = 'I', the infinity-norm of the
                   original matrix A.
    
         RCOND     (output) REAL
                   The reciprocal of  the  condition  number  of  the
                   matrix  A, computed as RCOND = 1/(ANORM * AINVNM),
                   where AINVNM is  an  estimate  of  the  1-norm  of
                   inv(A) computed in this routine.
    
         WORK      (workspace) REAL array, dimension (2*N)
    
         IWORK     (workspace) INTEGER array, dimension (N)
    
         INFO      (output) INTEGER
                   = 0:  successful exit
                   < 0:  if INFO = -i, the i-th argument had an ille-
                   gal value
    
    
    
    


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