DTRMV - perform 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*1 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.
PARAMETERS
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 per
formed as follows:
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 trian
gular.
DIAG = 'N' or 'n' A is not assumed to be unit
triangular.
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 con
tain 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 con
tain 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. 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 vec
tor x. On exit, X is overwritten with the tran
formed vector x.
INCX - INTEGER.
On entry, INCX specifies the increment for the ele
ments of X. INCX must not be zero. Unchanged on
exit.
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.
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