dtrti2(3)

NAME

DTRTI2 - compute the inverse of a real upper or lower tri

angular matrix

SYNOPSIS

SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO )
    CHARACTER      DIAG, UPLO
    INTEGER        INFO, LDA, N
    DOUBLE         PRECISION A( LDA, * )

PURPOSE

DTRTI2 computes the inverse of a real upper or lower tri

angular matrix. This is the Level 2 BLAS version of the algo

rithm.

ARGUMENTS

UPLO (input) CHARACTER*1

Specifies whether the matrix A is upper or lower

triangular. = 'U': Upper triangular
= 'L': Lower triangular

DIAG (input) CHARACTER*1

Specifies whether or not the matrix A is unit tri

angular. = 'N': Non-unit triangular
= 'U': Unit triangular

N (input) INTEGER

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

A (input/output) DOUBLE PRECISION array, dimension

(LDA,N)

On entry, the triangular matrix A. If UPLO = 'U',

the leading n by n upper triangular part of the array A contains

the upper triangular matrix, and the strictly lower triangular

part of A is not referenced. If UPLO = 'L', the leading n by n

lower triangular part of the array A contains the lower triangu

lar matrix, and the strictly upper triangular part of A is not

referenced. If DIAG = 'U', the diagonal elements of A are also

not referenced and are assumed to be 1.

On exit, the (triangular) inverse of the original

matrix, in the same storage format.

LDA (input) INTEGER

The leading dimension of the array A. LDA >=

max(1,N).

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -k, the k-th argument had an ille

gal value

LAPACK version 3.0 15 June 2000

DTRTI2(3)