55 lines
1.2 KiB
FortranFixed
55 lines
1.2 KiB
FortranFixed
SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
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* .. Scalar Arguments ..
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DOUBLE PRECISION C,S
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INTEGER INCX,INCY,N
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION DX(*),DY(*)
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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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* DROT applies a plane rotation.
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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 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,IX,IY
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* ..
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IF (N.LE.0) RETURN
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IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
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*
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* code for unequal increments or equal increments not equal
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* to 1
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*
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IX = 1
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IY = 1
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IF (INCX.LT.0) IX = (-N+1)*INCX + 1
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IF (INCY.LT.0) IY = (-N+1)*INCY + 1
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DO 10 I = 1,N
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DTEMP = C*DX(IX) + S*DY(IY)
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DY(IY) = C*DY(IY) - S*DX(IX)
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DX(IX) = DTEMP
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IX = IX + INCX
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IY = IY + INCY
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10 CONTINUE
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RETURN
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*
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* code for both increments equal to 1
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*
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20 DO 30 I = 1,N
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DTEMP = C*DX(I) + S*DY(I)
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DY(I) = C*DY(I) - S*DX(I)
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DX(I) = DTEMP
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30 CONTINUE
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RETURN
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END
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