116 lines
2.6 KiB
Fortran
116 lines
2.6 KiB
Fortran
*> \brief \b DAXPY
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* DOUBLE PRECISION DA
|
|
* INTEGER INCX,INCY,N
|
|
* ..
|
|
* .. Array Arguments ..
|
|
* DOUBLE PRECISION DX(*),DY(*)
|
|
* ..
|
|
*
|
|
*
|
|
*> \par Purpose:
|
|
* =============
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> DAXPY constant times a vector plus a vector.
|
|
*> uses unrolled loops for increments equal to one.
|
|
*> \endverbatim
|
|
*
|
|
* Authors:
|
|
* ========
|
|
*
|
|
*> \author Univ. of Tennessee
|
|
*> \author Univ. of California Berkeley
|
|
*> \author Univ. of Colorado Denver
|
|
*> \author NAG Ltd.
|
|
*
|
|
*> \date November 2011
|
|
*
|
|
*> \ingroup double_blas_level1
|
|
*
|
|
*> \par Further Details:
|
|
* =====================
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> jack dongarra, linpack, 3/11/78.
|
|
*> modified 12/3/93, array(1) declarations changed to array(*)
|
|
*> \endverbatim
|
|
*>
|
|
* =====================================================================
|
|
SUBROUTINE DAXPY(N,DA,DX,INCX,DY,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 ..
|
|
DOUBLE PRECISION DA
|
|
INTEGER INCX,INCY,N
|
|
* ..
|
|
* .. Array Arguments ..
|
|
DOUBLE PRECISION DX(*),DY(*)
|
|
* ..
|
|
*
|
|
* =====================================================================
|
|
*
|
|
* .. Local Scalars ..
|
|
INTEGER I,IX,IY,M,MP1
|
|
* ..
|
|
* .. Intrinsic Functions ..
|
|
INTRINSIC MOD
|
|
* ..
|
|
IF (N.LE.0) RETURN
|
|
IF (DA.EQ.0.0d0) RETURN
|
|
IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
|
|
*
|
|
* code for both increments equal to 1
|
|
*
|
|
*
|
|
* clean-up loop
|
|
*
|
|
M = MOD(N,4)
|
|
IF (M.NE.0) THEN
|
|
DO I = 1,M
|
|
DY(I) = DY(I) + DA*DX(I)
|
|
END DO
|
|
END IF
|
|
IF (N.LT.4) RETURN
|
|
MP1 = M + 1
|
|
DO I = MP1,N,4
|
|
DY(I) = DY(I) + DA*DX(I)
|
|
DY(I+1) = DY(I+1) + DA*DX(I+1)
|
|
DY(I+2) = DY(I+2) + DA*DX(I+2)
|
|
DY(I+3) = DY(I+3) + DA*DX(I+3)
|
|
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
|
|
DY(IY) = DY(IY) + DA*DX(IX)
|
|
IX = IX + INCX
|
|
IY = IY + INCY
|
|
END DO
|
|
END IF
|
|
RETURN
|
|
END
|