Annotation of rpl/lapack/blas/ddot.f, revision 1.8
1.8 ! bertrand 1: *> \brief \b DDOT
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: * Definition:
! 9: * ===========
! 10: *
! 11: * DOUBLE PRECISION FUNCTION DDOT(N,DX,INCX,DY,INCY)
! 12: *
! 13: * .. Scalar Arguments ..
! 14: * INTEGER INCX,INCY,N
! 15: * ..
! 16: * .. Array Arguments ..
! 17: * DOUBLE PRECISION DX(*),DY(*)
! 18: * ..
! 19: *
! 20: *
! 21: *> \par Purpose:
! 22: * =============
! 23: *>
! 24: *> \verbatim
! 25: *>
! 26: *> DDOT forms the dot product of two vectors.
! 27: *> uses unrolled loops for increments equal to one.
! 28: *> \endverbatim
! 29: *
! 30: * Authors:
! 31: * ========
! 32: *
! 33: *> \author Univ. of Tennessee
! 34: *> \author Univ. of California Berkeley
! 35: *> \author Univ. of Colorado Denver
! 36: *> \author NAG Ltd.
! 37: *
! 38: *> \date November 2011
! 39: *
! 40: *> \ingroup double_blas_level1
! 41: *
! 42: *> \par Further Details:
! 43: * =====================
! 44: *>
! 45: *> \verbatim
! 46: *>
! 47: *> jack dongarra, linpack, 3/11/78.
! 48: *> modified 12/3/93, array(1) declarations changed to array(*)
! 49: *> \endverbatim
! 50: *>
! 51: * =====================================================================
1.1 bertrand 52: DOUBLE PRECISION FUNCTION DDOT(N,DX,INCX,DY,INCY)
1.8 ! bertrand 53: *
! 54: * -- Reference BLAS level1 routine (version 3.4.0) --
! 55: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
! 56: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 57: * November 2011
! 58: *
1.1 bertrand 59: * .. Scalar Arguments ..
60: INTEGER INCX,INCY,N
61: * ..
62: * .. Array Arguments ..
63: DOUBLE PRECISION DX(*),DY(*)
64: * ..
65: *
66: * =====================================================================
67: *
68: * .. Local Scalars ..
69: DOUBLE PRECISION DTEMP
70: INTEGER I,IX,IY,M,MP1
71: * ..
72: * .. Intrinsic Functions ..
73: INTRINSIC MOD
74: * ..
75: DDOT = 0.0d0
76: DTEMP = 0.0d0
77: IF (N.LE.0) RETURN
1.7 bertrand 78: IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
1.1 bertrand 79: *
80: * code for both increments equal to 1
81: *
82: *
83: * clean-up loop
84: *
1.7 bertrand 85: M = MOD(N,5)
86: IF (M.NE.0) THEN
87: DO I = 1,M
88: DTEMP = DTEMP + DX(I)*DY(I)
89: END DO
90: IF (N.LT.5) THEN
91: DDOT=DTEMP
92: RETURN
93: END IF
94: END IF
95: MP1 = M + 1
96: DO I = MP1,N,5
1.1 bertrand 97: DTEMP = DTEMP + DX(I)*DY(I) + DX(I+1)*DY(I+1) +
1.7 bertrand 98: $ DX(I+2)*DY(I+2) + DX(I+3)*DY(I+3) + DX(I+4)*DY(I+4)
99: END DO
100: ELSE
101: *
102: * code for unequal increments or equal increments
103: * not equal to 1
104: *
105: IX = 1
106: IY = 1
107: IF (INCX.LT.0) IX = (-N+1)*INCX + 1
108: IF (INCY.LT.0) IY = (-N+1)*INCY + 1
109: DO I = 1,N
110: DTEMP = DTEMP + DX(IX)*DY(IY)
111: IX = IX + INCX
112: IY = IY + INCY
113: END DO
114: END IF
115: DDOT = DTEMP
1.1 bertrand 116: RETURN
117: END
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