65 lines
1.4 KiB
FortranFixed
65 lines
1.4 KiB
FortranFixed
SUBROUTINE DSCAL(N,DA,DX,INCX)
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* .. Scalar Arguments ..
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DOUBLE PRECISION DA
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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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* DSCAL scales a vector by a constant.
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* uses unrolled loops for increment equal to one.
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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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INTEGER I,M,MP1,NINCX
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MOD
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* ..
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IF (N.LE.0 .OR. INCX.LE.0) RETURN
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IF (INCX.EQ.1) THEN
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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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M = MOD(N,5)
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IF (M.NE.0) THEN
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DO I = 1,M
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DX(I) = DA*DX(I)
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END DO
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IF (N.LT.5) RETURN
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END IF
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MP1 = M + 1
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DO I = MP1,N,5
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DX(I) = DA*DX(I)
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DX(I+1) = DA*DX(I+1)
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DX(I+2) = DA*DX(I+2)
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DX(I+3) = DA*DX(I+3)
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DX(I+4) = DA*DX(I+4)
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END DO
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ELSE
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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 I = 1,NINCX,INCX
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DX(I) = DA*DX(I)
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END DO
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END IF
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RETURN
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END
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