```      SUBROUTINE ZHPMV(UPLO,N,ALPHA,AP,X,INCX,BETA,Y,INCY)
*     .. Scalar Arguments ..
DOUBLE COMPLEX ALPHA,BETA
INTEGER INCX,INCY,N
CHARACTER UPLO
*     ..
*     .. Array Arguments ..
DOUBLE COMPLEX AP(*),X(*),Y(*)
*     ..
*
*  Purpose
*  =======
*
*  ZHPMV  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 hermitian matrix, supplied 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*16      .
*           On entry, ALPHA specifies the scalar alpha.
*           Unchanged on exit.
*
*  AP     - COMPLEX*16       array of 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 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.
*           Before 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.
*           Note that the imaginary parts of the diagonal elements need
*           not be set and are assumed to be zero.
*           Unchanged on exit.
*
*  X      - COMPLEX*16       array of 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 elements of
*           X. INCX must not be zero.
*           Unchanged on exit.
*
*  BETA   - COMPLEX*16      .
*           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*16       array of dimension at least
*           ( 1 + ( n - 1 )*abs( INCY ) ).
*           Before entry, the incremented array Y must contain the n
*           element vector y. On exit, Y is overwritten by the updated
*           vector y.
*
*  INCY   - INTEGER.
*           On entry, INCY specifies the increment for the elements of
*           Y. INCY 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.
*
*
*     .. Parameters ..
DOUBLE COMPLEX ONE
PARAMETER (ONE= (1.0D+0,0.0D+0))
DOUBLE COMPLEX ZERO
PARAMETER (ZERO= (0.0D+0,0.0D+0))
*     ..
*     .. Local Scalars ..
DOUBLE COMPLEX TEMP1,TEMP2
INTEGER I,INFO,IX,IY,J,JX,JY,K,KK,KX,KY
*     ..
*     .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
*     ..
*     .. External Subroutines ..
EXTERNAL XERBLA
*     ..
*     .. Intrinsic Functions ..
INTRINSIC DBLE,DCONJG
*     ..
*
*     Test the input parameters.
*
INFO = 0
IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
INFO = 1
ELSE IF (N.LT.0) THEN
INFO = 2
ELSE IF (INCX.EQ.0) THEN
INFO = 6
ELSE IF (INCY.EQ.0) THEN
INFO = 9
END IF
IF (INFO.NE.0) THEN
CALL XERBLA('ZHPMV ',INFO)
RETURN
END IF
*
*     Quick return if possible.
*
IF ((N.EQ.0) .OR. ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
*
*     Set up the start points in  X  and  Y.
*
IF (INCX.GT.0) THEN
KX = 1
ELSE
KX = 1 - (N-1)*INCX
END IF
IF (INCY.GT.0) THEN
KY = 1
ELSE
KY = 1 - (N-1)*INCY
END IF
*
*     Start the operations. In this version the elements of the array AP
*     are accessed sequentially with one pass through AP.
*
*     First form  y := beta*y.
*
IF (BETA.NE.ONE) THEN
IF (INCY.EQ.1) THEN
IF (BETA.EQ.ZERO) THEN
DO 10 I = 1,N
Y(I) = ZERO
10             CONTINUE
ELSE
DO 20 I = 1,N
Y(I) = BETA*Y(I)
20             CONTINUE
END IF
ELSE
IY = KY
IF (BETA.EQ.ZERO) THEN
DO 30 I = 1,N
Y(IY) = ZERO
IY = IY + INCY
30             CONTINUE
ELSE
DO 40 I = 1,N
Y(IY) = BETA*Y(IY)
IY = IY + INCY
40             CONTINUE
END IF
END IF
END IF
IF (ALPHA.EQ.ZERO) RETURN
KK = 1
IF (LSAME(UPLO,'U')) THEN
*
*        Form  y  when AP contains the upper triangle.
*
IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
DO 60 J = 1,N
TEMP1 = ALPHA*X(J)
TEMP2 = ZERO
K = KK
DO 50 I = 1,J - 1
Y(I) = Y(I) + TEMP1*AP(K)
TEMP2 = TEMP2 + DCONJG(AP(K))*X(I)
K = K + 1
50             CONTINUE
Y(J) = Y(J) + TEMP1*DBLE(AP(KK+J-1)) + ALPHA*TEMP2
KK = KK + J
60         CONTINUE
ELSE
JX = KX
JY = KY
DO 80 J = 1,N
TEMP1 = ALPHA*X(JX)
TEMP2 = ZERO
IX = KX
IY = KY
DO 70 K = KK,KK + J - 2
Y(IY) = Y(IY) + TEMP1*AP(K)
TEMP2 = TEMP2 + DCONJG(AP(K))*X(IX)
IX = IX + INCX
IY = IY + INCY
70             CONTINUE
Y(JY) = Y(JY) + TEMP1*DBLE(AP(KK+J-1)) + ALPHA*TEMP2
JX = JX + INCX
JY = JY + INCY
KK = KK + J
80         CONTINUE
END IF
ELSE
*
*        Form  y  when AP contains the lower triangle.
*
IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
DO 100 J = 1,N
TEMP1 = ALPHA*X(J)
TEMP2 = ZERO
Y(J) = Y(J) + TEMP1*DBLE(AP(KK))
K = KK + 1
DO 90 I = J + 1,N
Y(I) = Y(I) + TEMP1*AP(K)
TEMP2 = TEMP2 + DCONJG(AP(K))*X(I)
K = K + 1
90             CONTINUE
Y(J) = Y(J) + ALPHA*TEMP2
KK = KK + (N-J+1)
100         CONTINUE
ELSE
JX = KX
JY = KY
DO 120 J = 1,N
TEMP1 = ALPHA*X(JX)
TEMP2 = ZERO
Y(JY) = Y(JY) + TEMP1*DBLE(AP(KK))
IX = JX
IY = JY
DO 110 K = KK + 1,KK + N - J
IX = IX + INCX
IY = IY + INCY
Y(IY) = Y(IY) + TEMP1*AP(K)
TEMP2 = TEMP2 + DCONJG(AP(K))*X(IX)
110             CONTINUE
Y(JY) = Y(JY) + ALPHA*TEMP2
JX = JX + INCX
JY = JY + INCY
KK = KK + (N-J+1)
120         CONTINUE
END IF
END IF
*
RETURN
*
*     End of ZHPMV .
*
END

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