SRC/stptri.f(3)            Library Functions Manual            SRC/stptri.f(3)

NAME
       SRC/stptri.f

SYNOPSIS
   Functions/Subroutines
       subroutine stptri (uplo, diag, n, ap, info)
           STPTRI

Function/Subroutine Documentation
   subroutine stptri (character uplo, character diag, integer n, real,
       dimension( * ) ap, integer info)
       STPTRI

       Purpose:


            STPTRI computes the inverse of a real upper or lower triangular
            matrix A stored in packed format.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     = 'U':  A is upper triangular;
                     = 'L':  A is lower triangular.

           DIAG

                     DIAG is CHARACTER*1
                     = 'N':  A is non-unit triangular;
                     = 'U':  A is unit triangular.

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           AP

                     AP is REAL array, dimension (N*(N+1)/2)
                     On entry, the upper or lower triangular matrix A, stored
                     columnwise in a linear array.  The j-th column of A is stored
                     in the array AP as follows:
                     if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
                     if UPLO = 'L', AP(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n.
                     See below for further details.
                     On exit, the (triangular) inverse of the original matrix, in
                     the same packed storage format.

           INFO

                     INFO is INTEGER
                     = 0:  successful exit
                     < 0:  if INFO = -i, the i-th argument had an illegal value
                     > 0:  if INFO = i, A(i,i) is exactly zero.  The triangular
                           matrix is singular and its inverse can not be computed.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Further Details:


             A triangular matrix A can be transferred to packed storage using one
             of the following program segments:

             UPLO = 'U':                      UPLO = 'L':

                   JC = 1                           JC = 1
                   DO 2 J = 1, N                    DO 2 J = 1, N
                      DO 1 I = 1, J                    DO 1 I = J, N
                         AP(JC+I-1) = A(I,J)              AP(JC+I-J) = A(I,J)
                 1    CONTINUE                    1    CONTINUE
                      JC = JC + J                      JC = JC + N - J + 1
                 2 CONTINUE                       2 CONTINUE

       Definition at line 116 of file stptri.f.

Author
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LAPACK                          Version 3.12.0                 SRC/stptri.f(3)