root / src / blas / drot.f @ 11
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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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* applies a plane rotation. |
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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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* .. 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 |