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| 1 | SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S) |
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| 2 | * .. Scalar Arguments .. |
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| 3 | DOUBLE PRECISION C,S |
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| 4 | INTEGER INCX,INCY,N |
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| 5 | * .. |
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| 6 | * .. Array Arguments .. |
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| 7 | DOUBLE PRECISION DX(*),DY(*) |
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| 8 | * .. |
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| 9 | * |
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| 10 | * Purpose |
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| 11 | * ======= |
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| 12 | * |
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| 13 | * applies a plane rotation. |
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| 14 | * jack dongarra, linpack, 3/11/78. |
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| 15 | * modified 12/3/93, array(1) declarations changed to array(*) |
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| 16 | * |
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| 17 | * |
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| 18 | * .. Local Scalars .. |
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| 19 | DOUBLE PRECISION DTEMP |
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| 20 | INTEGER I,IX,IY |
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| 21 | * .. |
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| 22 | IF (N.LE.0) RETURN |
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| 23 | IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20 |
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| 24 | * |
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| 25 | * code for unequal increments or equal increments not equal |
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| 26 | * to 1 |
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| 27 | * |
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| 28 | IX = 1 |
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| 29 | IY = 1 |
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| 30 | IF (INCX.LT.0) IX = (-N+1)*INCX + 1 |
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| 31 | IF (INCY.LT.0) IY = (-N+1)*INCY + 1 |
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| 32 | DO 10 I = 1,N |
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| 33 | DTEMP = C*DX(IX) + S*DY(IY) |
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| 34 | DY(IY) = C*DY(IY) - S*DX(IX) |
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| 35 | DX(IX) = DTEMP |
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| 36 | IX = IX + INCX |
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| 37 | IY = IY + INCY |
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| 38 | 10 CONTINUE |
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| 39 | RETURN |
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| 40 | * |
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| 41 | * code for both increments equal to 1 |
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| 42 | * |
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| 43 | 20 DO 30 I = 1,N |
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| 44 | DTEMP = C*DX(I) + S*DY(I) |
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| 45 | DY(I) = C*DY(I) - S*DX(I) |
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| 46 | DX(I) = DTEMP |
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| 47 | 30 CONTINUE |
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| 48 | RETURN |
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| 49 | END |
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