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