63 lines
1.4 KiB
Fortran
63 lines
1.4 KiB
Fortran
DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
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* .. Scalar Arguments ..
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INTEGER INCX,N
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION DX(*)
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* ..
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*
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* Purpose
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* =======
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*
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* DASUM takes the sum of the absolute values.
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*
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* Further Details
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* ===============
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*
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* jack dongarra, linpack, 3/11/78.
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* modified 3/93 to return if incx .le. 0.
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* modified 12/3/93, array(1) declarations changed to array(*)
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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DOUBLE PRECISION DTEMP
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INTEGER I,M,MP1,NINCX
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DABS,MOD
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* ..
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DASUM = 0.0d0
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DTEMP = 0.0d0
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IF (N.LE.0 .OR. INCX.LE.0) RETURN
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IF (INCX.EQ.1) GO TO 20
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*
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* code for increment not equal to 1
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*
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NINCX = N*INCX
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DO 10 I = 1,NINCX,INCX
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DTEMP = DTEMP + DABS(DX(I))
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10 CONTINUE
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DASUM = DTEMP
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RETURN
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*
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* code for increment equal to 1
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*
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*
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* clean-up loop
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*
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20 M = MOD(N,6)
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IF (M.EQ.0) GO TO 40
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DO 30 I = 1,M
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DTEMP = DTEMP + DABS(DX(I))
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30 CONTINUE
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IF (N.LT.6) GO TO 60
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40 MP1 = M + 1
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DO 50 I = MP1,N,6
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DTEMP = DTEMP + DABS(DX(I)) + DABS(DX(I+1)) + DABS(DX(I+2)) +
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+ DABS(DX(I+3)) + DABS(DX(I+4)) + DABS(DX(I+5))
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50 CONTINUE
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60 DASUM = DTEMP
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RETURN
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END
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