DTRMV(1) BLAS routine DTRMV(1)NAME
DTRMV - performs one of the matrix-vector operations x := A*x, or x
:= A'*x,
SYNOPSIS
SUBROUTINE DTRMV(UPLO,TRANS,DIAG,N,A,LDA,X,INCX)
INTEGER INCX,LDA,N
CHARACTER DIAG,TRANS,UPLO
DOUBLE PRECISION
A(LDA,*),X(*)
PURPOSE
DTRMV performs one of the matrix-vector operations
where x is an n element vector and A is an n by n unit, or non-unit,
upper or lower triangular matrix.
ARGUMENTS
UPLO - 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.
Unchanged on exit.
TRANS - CHARACTER*1.
On entry, TRANS specifies the operation to be performed as fol‐
lows:
TRANS = 'N' or 'n' x := A*x.
TRANS = 'T' or 't' x := A'*x.
TRANS = 'C' or 'c' x := A'*x.
Unchanged on exit.
DIAG - 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.
Unchanged on exit.
N - INTEGER.
On entry, N specifies the order of the matrix A. N must be at
least zero. Unchanged on exit.
A - DOUBLE PRECISION array of 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 refer‐
enced. Before entry with UPLO = 'L' or 'l', the leading n by n
lower triangular part of the array A must contain the lower tri‐
angular 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. Unchanged on exit.
LDA - 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 ).
Unchanged on exit.
X - DOUBLE PRECISION array of dimension at least
( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented
array X must contain the n element vector x. On exit, X is over‐
written with the tranformed vector x.
INCX - INTEGER.
On entry, INCX specifies the increment for the elements of X.
INCX must not be zero. Unchanged on exit.
FURTHER DETAILS
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.
BLAS routine November 2008 DTRMV(1)