lammps/lib/linalg/zdotc.f

102 lines
2.3 KiB
Fortran

*> \brief \b ZDOTC
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* COMPLEX*16 FUNCTION ZDOTC(N,ZX,INCX,ZY,INCY)
*
* .. Scalar Arguments ..
* INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
* COMPLEX*16 ZX(*),ZY(*)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> ZDOTC forms the dot product of a vector.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup complex16_blas_level1
*
*> \par Further Details:
* =====================
*>
*> \verbatim
*>
*> jack dongarra, 3/11/78.
*> modified 12/3/93, array(1) declarations changed to array(*)
*> \endverbatim
*>
* =====================================================================
COMPLEX*16 FUNCTION ZDOTC(N,ZX,INCX,ZY,INCY)
*
* -- Reference BLAS level1 routine (version 3.4.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
COMPLEX*16 ZX(*),ZY(*)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
COMPLEX*16 ZTEMP
INTEGER I,IX,IY
* ..
* .. Intrinsic Functions ..
INTRINSIC DCONJG
* ..
ZTEMP = (0.0d0,0.0d0)
ZDOTC = (0.0d0,0.0d0)
IF (N.LE.0) RETURN
IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
*
* code for both increments equal to 1
*
DO I = 1,N
ZTEMP = ZTEMP + DCONJG(ZX(I))*ZY(I)
END DO
ELSE
*
* code for unequal increments or equal increments
* not equal to 1
*
IX = 1
IY = 1
IF (INCX.LT.0) IX = (-N+1)*INCX + 1
IF (INCY.LT.0) IY = (-N+1)*INCY + 1
DO I = 1,N
ZTEMP = ZTEMP + DCONJG(ZX(IX))*ZY(IY)
IX = IX + INCX
IY = IY + INCY
END DO
END IF
ZDOTC = ZTEMP
RETURN
END