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LAPACK 3.3.1
Linear Algebra PACKage
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LAPACK 3.3.1
Linear Algebra PACKage
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00001 SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY) 00002 * .. Scalar Arguments .. 00003 DOUBLE PRECISION DA 00004 INTEGER INCX,INCY,N 00005 * .. 00006 * .. Array Arguments .. 00007 DOUBLE PRECISION DX(*),DY(*) 00008 * .. 00009 * 00010 * Purpose 00011 * ======= 00012 * 00013 * DAXPY constant times a vector plus a vector. 00014 * uses unrolled loops for increments equal to one. 00015 * 00016 * Further Details 00017 * =============== 00018 * 00019 * jack dongarra, linpack, 3/11/78. 00020 * modified 12/3/93, array(1) declarations changed to array(*) 00021 * 00022 * ===================================================================== 00023 * 00024 * .. Local Scalars .. 00025 INTEGER I,IX,IY,M,MP1 00026 * .. 00027 * .. Intrinsic Functions .. 00028 INTRINSIC MOD 00029 * .. 00030 IF (N.LE.0) RETURN 00031 IF (DA.EQ.0.0d0) RETURN 00032 IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN 00033 * 00034 * code for both increments equal to 1 00035 * 00036 * 00037 * clean-up loop 00038 * 00039 M = MOD(N,4) 00040 IF (M.NE.0) THEN 00041 DO I = 1,M 00042 DY(I) = DY(I) + DA*DX(I) 00043 END DO 00044 END IF 00045 IF (N.LT.4) RETURN 00046 MP1 = M + 1 00047 DO I = MP1,N,4 00048 DY(I) = DY(I) + DA*DX(I) 00049 DY(I+1) = DY(I+1) + DA*DX(I+1) 00050 DY(I+2) = DY(I+2) + DA*DX(I+2) 00051 DY(I+3) = DY(I+3) + DA*DX(I+3) 00052 END DO 00053 ELSE 00054 * 00055 * code for unequal increments or equal increments 00056 * not equal to 1 00057 * 00058 IX = 1 00059 IY = 1 00060 IF (INCX.LT.0) IX = (-N+1)*INCX + 1 00061 IF (INCY.LT.0) IY = (-N+1)*INCY + 1 00062 DO I = 1,N 00063 DY(IY) = DY(IY) + DA*DX(IX) 00064 IX = IX + INCX 00065 IY = IY + INCY 00066 END DO 00067 END IF 00068 RETURN 00069 END
1.7.3 
