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Technical Reference: Base Operating System and Extensions , Volume 2
Performs matrixvector operations
using a packed Hermitian matrix.
BLAS Library
(libblas.a)
SUBROUTINE CHPMV(UPLO, N, ALPHA, AP, X,
INCX, BETA, Y, INCY)
COMPLEX ALPHA, BETA
INTEGER INCX, INCY, N
CHARACTER*1 UPLO
COMPLEX AP(*), X(*), Y(*)
SUBROUTINE ZHPMV
COMPLEX*16 ALPHA,BETA
INTEGER INCX,INCY,N
CHARACTER*1 UPLO
COMPLEX*16 AP(*), X(*), Y(*)
The CHPMV or
ZHPMV subroutine performs the matrixvector 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 Hermitian matrix, supplied in packed form.
UPLO
 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
 On entry, N specifies the order of the matrix
A; N must be at least 0; unchanged on
exit.

ALPHA
 On entry, ALPHA specifies the scalar alpha; unchanged on
exit.

AP
 A vector of dimension at least ( ( N * (N+1) )/2
); on entry with UPLO = 'U' or 'u', the
array AP must contain the upper triangular part of the Hermitian
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; on entry
with UPLO = 'L' or 'l', the array AP
must contain the lower triangular part of the Hermitian matrix packed
sequentially, column by column, so that AP(1) contains
A(1,1), AP(2) and AP(3) contain
A(2,1) and A(3,1) respectively, and so on. The
imaginary parts of the diagonal elements need not be set and are assumed to be
0; unchanged on exit.

X
 A vector of dimension at least (1 + (N1) * abs(
INCX ) ); on entry, the incremented array X must
contain the N element vector x; unchanged on exit.

INCX
 On entry, INCX specifies the increment for the elements of
X; INCX must not be 0; unchanged on
exit.

BETA
 On entry, BETA specifies the scalar beta; when
BETA is supplied as 0 then Y need not be set on
input; unchanged on exit.

Y
 A vector of dimension at least (1 + (N1) * abs(
INCY ) ); on entry, the incremented array Y must
contain the N element vector y; on exit, Y is
overwritten by the updated vector y.

INCY
 On entry, INCY specifies the increment for the elements of
Y; INCY must not be 0; unchanged on
exit.

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