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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 algorithm. 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 triangular 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 illegal value