strti2(3S)

NAME
     STRTI2 - compute the inverse of a real upper or lower triangular matrix

SYNOPSIS
     SUBROUTINE STRTI2( UPLO, DIAG, N, A, LDA, INFO )

         CHARACTER      DIAG, UPLO

         INTEGER        INFO, LDA, N

         REAL           A( LDA, * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

PURPOSE
     STRTI2 computes the inverse of a real upper or lower triangular 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 triangular.  = 'N':
             Non-unit triangular
             = 'U':  Unit triangular

     N       (input) INTEGER
             The order of the matrix A.  N >= 0.

     A       (input/output) REAL 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

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

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