Note: this is a BLAS routine and is not in libslatec.a
*DECK STRSV SUBROUTINE STRSV (UPLO, TRANS, DIAG, N, A, LDA, X, INCX) C***BEGIN PROLOGUE STRSV C***PURPOSE Solve a real triangular system of linear equations. C***LIBRARY SLATEC (BLAS) C***CATEGORY D1B4 C***TYPE SINGLE PRECISION (STRSV-S, DTRSV-D, CTRSV-C) C***KEYWORDS LEVEL 2 BLAS, LINEAR ALGEBRA C***AUTHOR Dongarra, J. J., (ANL) C Du Croz, J., (NAG) C Hammarling, S., (NAG) C Hanson, R. J., (SNLA) C***DESCRIPTION C C STRSV solves one of the systems of equations C C A*x = b, or A'*x = b, C C where b and x are n element vectors and A is an n by n unit, or C non-unit, upper or lower triangular matrix. C C No test for singularity or near-singularity is included in this C routine. Such tests must be performed before calling this routine. C C Parameters C ========== C C UPLO - CHARACTER*1. C On entry, UPLO specifies whether the matrix is an upper or C lower triangular matrix as follows: C C UPLO = 'U' or 'u' A is an upper triangular matrix. C C UPLO = 'L' or 'l' A is a lower triangular matrix. C C Unchanged on exit. C C TRANS - CHARACTER*1. C On entry, TRANS specifies the equations to be solved as C follows: C C TRANS = 'N' or 'n' A*x = b. C C TRANS = 'T' or 't' A'*x = b. C C TRANS = 'C' or 'c' A'*x = b. C C Unchanged on exit. C C DIAG - CHARACTER*1. C On entry, DIAG specifies whether or not A is unit C triangular as follows: C C DIAG = 'U' or 'u' A is assumed to be unit triangular. C C DIAG = 'N' or 'n' A is not assumed to be unit C triangular. C C Unchanged on exit. C C N - INTEGER. C On entry, N specifies the order of the matrix A. C N must be at least zero. C Unchanged on exit. C C A - REAL array of DIMENSION ( LDA, n). C Before entry with UPLO = 'U' or 'u', the leading n by n C upper triangular part of the array A must contain the upper C triangular matrix and the strictly lower triangular part of C A is not referenced. C Before entry with UPLO = 'L' or 'l', the leading n by n C lower triangular part of the array A must contain the lower C triangular matrix and the strictly upper triangular part of C A is not referenced. C Note that when DIAG = 'U' or 'u', the diagonal elements of C A are not referenced either, but are assumed to be unity. C Unchanged on exit. C C LDA - INTEGER. C On entry, LDA specifies the first dimension of A as declared C in the calling (sub) program. LDA must be at least C max( 1, n ). C Unchanged on exit. C C X - REAL array of dimension at least C ( 1 + ( n - 1 )*abs( INCX ) ). C Before entry, the incremented array X must contain the n C element right-hand side vector b. On exit, X is overwritten C with the solution vector x. C C INCX - INTEGER. C On entry, INCX specifies the increment for the elements of C X. INCX must not be zero. C Unchanged on exit. C C***REFERENCES Dongarra, J. J., Du Croz, J., Hammarling, S., and C Hanson, R. J. An extended set of Fortran basic linear C algebra subprograms. ACM TOMS, Vol. 14, No. 1, C pp. 1-17, March 1988. C***ROUTINES CALLED LSAME, XERBLA C***REVISION HISTORY (YYMMDD) C 861022 DATE WRITTEN C 910605 Modified to meet SLATEC prologue standards. Only comment C lines were modified. (BKS) C***END PROLOGUE STRSV