dtrsv()

subroutine dtrsv	(	character	uplo,
		character	trans,
		character	diag,
		integer	n,
		double precision, dimension(lda,*)	a,
		integer	lda,
		double precision, dimension(*)	x,
		integer	incx )

DTRSV

Purpose:

!>
!> DTRSV  solves one of the systems of equations
!>
!>    A*x = b,   or   A**T*x = b,
!>
!> where b and x are n element vectors and A is an n by n unit, or
!> non-unit, upper or lower triangular matrix.
!>
!> No test for singularity or near-singularity is included in this
!> routine. Such tests must be performed before calling this routine.
!> 

Parameters

[in]	UPLO	!> UPLO is CHARACTER*1 !> On entry, UPLO specifies whether the matrix is an upper or !> lower triangular matrix as follows: !> !> UPLO = 'U' or 'u' A is an upper triangular matrix. !> !> UPLO = 'L' or 'l' A is a lower triangular matrix. !>
[in]	TRANS	!> TRANS is CHARACTER*1 !> On entry, TRANS specifies the equations to be solved as !> follows: !> !> TRANS = 'N' or 'n' A*x = b. !> !> TRANS = 'T' or 't' A**T*x = b. !> !> TRANS = 'C' or 'c' A**T*x = b. !>
[in]	DIAG	!> DIAG is CHARACTER*1 !> On entry, DIAG specifies whether or not A is unit !> triangular as follows: !> !> DIAG = 'U' or 'u' A is assumed to be unit triangular. !> !> DIAG = 'N' or 'n' A is not assumed to be unit !> triangular. !>
[in]	N	!> N is INTEGER !> On entry, N specifies the order of the matrix A. !> N must be at least zero. !>
[in]	A	!> A is DOUBLE PRECISION array, dimension ( LDA, N ) !> Before entry with UPLO = 'U' or 'u', the leading n by n !> upper triangular part of the array A must contain the upper !> triangular matrix and the strictly lower triangular part of !> A is not referenced. !> Before entry with UPLO = 'L' or 'l', the leading n by n !> lower triangular part of the array A must contain the lower !> triangular matrix and the strictly upper triangular part of !> A is not referenced. !> Note that when DIAG = 'U' or 'u', the diagonal elements of !> A are not referenced either, but are assumed to be unity. !>
[in]	LDA	!> LDA is INTEGER !> On entry, LDA specifies the first dimension of A as declared !> in the calling (sub) program. LDA must be at least !> max( 1, n ). !>
[in,out]	X	!> X is DOUBLE PRECISION array, dimension at least !> ( 1 + ( n - 1 )*abs( INCX ) ). !> Before entry, the incremented array X must contain the n !> element right-hand side vector b. On exit, X is overwritten !> with the solution vector x. !>
[in]	INCX	!> INCX is INTEGER !> On entry, INCX specifies the increment for the elements of !> X. INCX must not be zero. !> !> Level 2 Blas routine. !> !> -- Written on 22-October-1986. !> Jack Dongarra, Argonne National Lab. !> Jeremy Du Croz, Nag Central Office. !> Sven Hammarling, Nag Central Office. !> Richard Hanson, Sandia National Labs. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.