CSPMV - perform the matrix-vector operation y :=
alpha*A*x + beta*y,
SYNOPSIS
SUBROUTINE CSPMV( UPLO, N, ALPHA, AP, X, INCX, BETA, Y,
INCY )
CHARACTER UPLO
INTEGER INCX, INCY, N
COMPLEX ALPHA, BETA
COMPLEX AP( * ), X( * ), Y( * )
PURPOSE
CSPMV performs the matrix-vector operation y := alpha*A*x
+ beta*y, where alpha and beta are scalars, x and y are n
element vectors and A is an n by n symmetric matrix, sup
plied in packed form.
ARGUMENTS
UPLO - CHARACTER*1
On entry, UPLO specifies whether the upper or lower
triangular part of the matrix A is supplied in the
packed array AP as follows:
UPLO = 'U' or 'u' The upper triangular part of A
is supplied in AP.
UPLO = 'L' or 'l' The lower triangular part of A
is supplied in AP.
Unchanged on exit.
N - INTEGER
On entry, N specifies the order of the matrix A. N
must be at least zero. Unchanged on exit.
ALPHA - COMPLEX
On entry, ALPHA specifies the scalar alpha.
Unchanged on exit.
AP - COMPLEX array, dimension at least
( ( N*( N + 1 ) )/2 ). Before entry, with UPLO =
'U' or 'u', the array AP must contain the upper
triangular part of the symmetric matrix packed
sequentially, column by column, so that AP( 1 )
contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a(
1, 2 ) and a( 2, 2 ) respectively, and so on.
Before entry, with UPLO = 'L' or 'l', the array AP
must contain the lower triangular part of the
column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 )
and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respec
tively, and so on. Unchanged on exit.
X - COMPLEX array, dimension at least
( 1 + ( N - 1 )*abs( INCX ) ). Before entry, the
incremented array X must contain the N- element
vector x. Unchanged on exit.
INCX - INTEGER
On entry, INCX specifies the increment for the ele
ments of X. INCX must not be zero. Unchanged on
exit.
BETA - COMPLEX
On entry, BETA specifies the scalar beta. When BETA
is supplied as zero then Y need not be set on
input. Unchanged on exit.
Y - COMPLEX array, dimension at least
( 1 + ( N - 1 )*abs( INCY ) ). Before entry, the
incremented array Y must contain the n element vec
tor y. On exit, Y is overwritten by the updated
vector y.
INCY - INTEGER
On entry, INCY specifies the increment for the ele
ments of Y. INCY must not be zero. Unchanged on
exit.
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