1: SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
2: * .. Scalar Arguments ..
3: DOUBLE PRECISION C,S
4: INTEGER INCX,INCY,N
5: * ..
6: * .. Array Arguments ..
7: DOUBLE PRECISION DX(*),DY(*)
8: * ..
9: *
10: * Purpose
11: * =======
12: *
13: * DROT applies a plane rotation.
14: *
15: * Further Details
16: * ===============
17: *
18: * jack dongarra, linpack, 3/11/78.
19: * modified 12/3/93, array(1) declarations changed to array(*)
20: *
21: * =====================================================================
22: *
23: * .. Local Scalars ..
24: DOUBLE PRECISION DTEMP
25: INTEGER I,IX,IY
26: * ..
27: IF (N.LE.0) RETURN
28: IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
29: *
30: * code for unequal increments or equal increments not equal
31: * to 1
32: *
33: IX = 1
34: IY = 1
35: IF (INCX.LT.0) IX = (-N+1)*INCX + 1
36: IF (INCY.LT.0) IY = (-N+1)*INCY + 1
37: DO 10 I = 1,N
38: DTEMP = C*DX(IX) + S*DY(IY)
39: DY(IY) = C*DY(IY) - S*DX(IX)
40: DX(IX) = DTEMP
41: IX = IX + INCX
42: IY = IY + INCY
43: 10 CONTINUE
44: RETURN
45: *
46: * code for both increments equal to 1
47: *
48: 20 DO 30 I = 1,N
49: DTEMP = C*DX(I) + S*DY(I)
50: DY(I) = C*DY(I) - S*DX(I)
51: DX(I) = DTEMP
52: 30 CONTINUE
53: RETURN
54: END
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