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C Derived from lapack
PROGRAM test
DOUBLE PRECISION DA
INTEGER I, N
DOUBLE PRECISION DX(9),DY(9)
EXTERNAL DAXPY
N=5
DA=1.0
DATA DX/-2, -1, -3, -4, 1, 2, 10, 15, 14/
DATA DY/0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0/
CALL DAXPY (N,DA,DX,DY)
DO 10 I = 1, N
if (DX(I).ne.DY(I)) call abort
10 CONTINUE
STOP
END
SUBROUTINE DAXPY(N,DA,DX,DY)
DOUBLE PRECISION DA
INTEGER N
DOUBLE PRECISION DX(*),DY(*)
INTEGER I,IX,IY,M,MP1
INTRINSIC MOD
IF (N.LE.0) RETURN
20 M = MOD(N,4)
IF (M.EQ.0) GO TO 40
DO 30 I = 1,M
DY(I) = DY(I) + DA*DX(I)
30 CONTINUE
IF (N.LT.4) RETURN
40 MP1 = M + 1
DO 50 I = MP1,N,4
DY(I) = DY(I) + DA*DX(I)
DY(I+1) = DY(I+1) + DA*DX(I+1)
DY(I+2) = DY(I+2) + DA*DX(I+2)
DY(I+3) = DY(I+3) + DA*DX(I+3)
50 CONTINUE
RETURN
END
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