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)