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stptri.f(3) LAPACK stptri.f(3)

NAME

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.

Date:

December 2016

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 119 of file stptri.f.

Author

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Tue Nov 14 2017 Version 3.8.0