Annotation of rpl/lapack/blas/daxpy.f, revision 1.8
1.8 ! bertrand 1: *> \brief \b DAXPY
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: * Definition:
! 9: * ===========
! 10: *
! 11: * SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
! 12: *
! 13: * .. Scalar Arguments ..
! 14: * DOUBLE PRECISION DA
! 15: * INTEGER INCX,INCY,N
! 16: * ..
! 17: * .. Array Arguments ..
! 18: * DOUBLE PRECISION DX(*),DY(*)
! 19: * ..
! 20: *
! 21: *
! 22: *> \par Purpose:
! 23: * =============
! 24: *>
! 25: *> \verbatim
! 26: *>
! 27: *> DAXPY constant times a vector plus a vector.
! 28: *> uses unrolled loops for increments equal to one.
! 29: *> \endverbatim
! 30: *
! 31: * Authors:
! 32: * ========
! 33: *
! 34: *> \author Univ. of Tennessee
! 35: *> \author Univ. of California Berkeley
! 36: *> \author Univ. of Colorado Denver
! 37: *> \author NAG Ltd.
! 38: *
! 39: *> \date November 2011
! 40: *
! 41: *> \ingroup double_blas_level1
! 42: *
! 43: *> \par Further Details:
! 44: * =====================
! 45: *>
! 46: *> \verbatim
! 47: *>
! 48: *> jack dongarra, linpack, 3/11/78.
! 49: *> modified 12/3/93, array(1) declarations changed to array(*)
! 50: *> \endverbatim
! 51: *>
! 52: * =====================================================================
1.1 bertrand 53: SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
1.8 ! bertrand 54: *
! 55: * -- Reference BLAS level1 routine (version 3.4.0) --
! 56: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
! 57: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 58: * November 2011
! 59: *
1.1 bertrand 60: * .. Scalar Arguments ..
61: DOUBLE PRECISION DA
62: INTEGER INCX,INCY,N
63: * ..
64: * .. Array Arguments ..
65: DOUBLE PRECISION DX(*),DY(*)
66: * ..
67: *
68: * =====================================================================
69: *
70: * .. Local Scalars ..
71: INTEGER I,IX,IY,M,MP1
72: * ..
73: * .. Intrinsic Functions ..
74: INTRINSIC MOD
75: * ..
76: IF (N.LE.0) RETURN
77: IF (DA.EQ.0.0d0) RETURN
1.7 bertrand 78: IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
79: *
80: * code for both increments equal to 1
81: *
82: *
83: * clean-up loop
84: *
85: M = MOD(N,4)
86: IF (M.NE.0) THEN
87: DO I = 1,M
88: DY(I) = DY(I) + DA*DX(I)
89: END DO
90: END IF
91: IF (N.LT.4) RETURN
92: MP1 = M + 1
93: DO I = MP1,N,4
94: DY(I) = DY(I) + DA*DX(I)
95: DY(I+1) = DY(I+1) + DA*DX(I+1)
96: DY(I+2) = DY(I+2) + DA*DX(I+2)
97: DY(I+3) = DY(I+3) + DA*DX(I+3)
98: END DO
99: ELSE
1.1 bertrand 100: *
101: * code for unequal increments or equal increments
102: * not equal to 1
103: *
1.7 bertrand 104: IX = 1
105: IY = 1
106: IF (INCX.LT.0) IX = (-N+1)*INCX + 1
107: IF (INCY.LT.0) IY = (-N+1)*INCY + 1
108: DO I = 1,N
1.1 bertrand 109: DY(IY) = DY(IY) + DA*DX(IX)
110: IX = IX + INCX
111: IY = IY + INCY
1.7 bertrand 112: END DO
113: END IF
1.1 bertrand 114: RETURN
115: END
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