Annotation of rpl/lapack/blas/ddot.f, revision 1.1
1.1 ! bertrand 1: DOUBLE PRECISION FUNCTION DDOT(N,DX,INCX,DY,INCY)
! 2: * .. Scalar Arguments ..
! 3: INTEGER INCX,INCY,N
! 4: * ..
! 5: * .. Array Arguments ..
! 6: DOUBLE PRECISION DX(*),DY(*)
! 7: * ..
! 8: *
! 9: * Purpose
! 10: * =======
! 11: *
! 12: * DDOT forms the dot product of two vectors.
! 13: * uses unrolled loops for increments equal to one.
! 14: *
! 15: * Further Details
! 16: * ===============
! 17: *
! 18: * jack dongarra, linpack, 3/11/78.
! 19: * modified 12/3/93, array(1) declarations changed to array(*)
! 20: *
! 21: * =====================================================================
! 22: *
! 23: * .. Local Scalars ..
! 24: DOUBLE PRECISION DTEMP
! 25: INTEGER I,IX,IY,M,MP1
! 26: * ..
! 27: * .. Intrinsic Functions ..
! 28: INTRINSIC MOD
! 29: * ..
! 30: DDOT = 0.0d0
! 31: DTEMP = 0.0d0
! 32: IF (N.LE.0) RETURN
! 33: IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
! 34: *
! 35: * code for unequal increments or equal increments
! 36: * not equal to 1
! 37: *
! 38: IX = 1
! 39: IY = 1
! 40: IF (INCX.LT.0) IX = (-N+1)*INCX + 1
! 41: IF (INCY.LT.0) IY = (-N+1)*INCY + 1
! 42: DO 10 I = 1,N
! 43: DTEMP = DTEMP + DX(IX)*DY(IY)
! 44: IX = IX + INCX
! 45: IY = IY + INCY
! 46: 10 CONTINUE
! 47: DDOT = DTEMP
! 48: RETURN
! 49: *
! 50: * code for both increments equal to 1
! 51: *
! 52: *
! 53: * clean-up loop
! 54: *
! 55: 20 M = MOD(N,5)
! 56: IF (M.EQ.0) GO TO 40
! 57: DO 30 I = 1,M
! 58: DTEMP = DTEMP + DX(I)*DY(I)
! 59: 30 CONTINUE
! 60: IF (N.LT.5) GO TO 60
! 61: 40 MP1 = M + 1
! 62: DO 50 I = MP1,N,5
! 63: DTEMP = DTEMP + DX(I)*DY(I) + DX(I+1)*DY(I+1) +
! 64: + DX(I+2)*DY(I+2) + DX(I+3)*DY(I+3) + DX(I+4)*DY(I+4)
! 65: 50 CONTINUE
! 66: 60 DDOT = DTEMP
! 67: RETURN
! 68: END
CVSweb interface <joel.bertrand@systella.fr>