| 1 | SUBROUTINE CSROT( N, CX, INCX, CY, INCY, C, S ) |
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| 2 | * |
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| 3 | * .. Scalar Arguments .. |
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| 4 | INTEGER INCX, INCY, N |
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| 5 | REAL C, S |
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| 6 | * .. |
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| 7 | * .. Array Arguments .. |
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| 8 | COMPLEX CX( * ), CY( * ) |
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| 9 | * .. |
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| 10 | * |
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| 11 | * Purpose |
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| 12 | * ======= |
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| 13 | * |
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| 14 | * Applies a plane rotation, where the cos and sin (c and s) are real |
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| 15 | * and the vectors cx and cy are complex. |
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| 16 | * jack dongarra, linpack, 3/11/78. |
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| 17 | * |
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| 18 | * Arguments |
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| 19 | * ========== |
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| 20 | * |
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| 21 | * N (input) INTEGER |
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| 22 | * On entry, N specifies the order of the vectors cx and cy. |
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| 23 | * N must be at least zero. |
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| 24 | * Unchanged on exit. |
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| 25 | * |
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| 26 | * CX (input) COMPLEX array, dimension at least |
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| 27 | * ( 1 + ( N - 1 )*abs( INCX ) ). |
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| 28 | * Before entry, the incremented array CX must contain the n |
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| 29 | * element vector cx. On exit, CX is overwritten by the updated |
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| 30 | * vector cx. |
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| 31 | * |
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| 32 | * INCX (input) INTEGER |
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| 33 | * On entry, INCX specifies the increment for the elements of |
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| 34 | * CX. INCX must not be zero. |
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| 35 | * Unchanged on exit. |
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| 36 | * |
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| 37 | * CY (input) COMPLEX array, dimension at least |
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| 38 | * ( 1 + ( N - 1 )*abs( INCY ) ). |
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| 39 | * Before entry, the incremented array CY must contain the n |
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| 40 | * element vector cy. On exit, CY is overwritten by the updated |
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| 41 | * vector cy. |
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| 42 | * |
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| 43 | * INCY (input) INTEGER |
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| 44 | * On entry, INCY specifies the increment for the elements of |
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| 45 | * CY. INCY must not be zero. |
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| 46 | * Unchanged on exit. |
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| 47 | * |
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| 48 | * C (input) REAL |
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| 49 | * On entry, C specifies the cosine, cos. |
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| 50 | * Unchanged on exit. |
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| 51 | * |
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| 52 | * S (input) REAL |
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| 53 | * On entry, S specifies the sine, sin. |
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| 54 | * Unchanged on exit. |
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| 55 | * |
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| 56 | * ===================================================================== |
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| 57 | * |
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| 58 | * .. Local Scalars .. |
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| 59 | INTEGER I, IX, IY |
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| 60 | COMPLEX CTEMP |
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| 61 | * .. |
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| 62 | * .. Executable Statements .. |
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| 63 | * |
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| 64 | IF( N.LE.0 ) |
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| 65 | $ RETURN |
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| 66 | IF( INCX.EQ.1 .AND. INCY.EQ.1 ) |
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| 67 | $ GO TO 20 |
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| 68 | * |
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| 69 | * code for unequal increments or equal increments not equal |
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| 70 | * to 1 |
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| 71 | * |
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| 72 | IX = 1 |
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| 73 | IY = 1 |
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| 74 | IF( INCX.LT.0 ) |
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| 75 | $ IX = ( -N+1 )*INCX + 1 |
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| 76 | IF( INCY.LT.0 ) |
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| 77 | $ IY = ( -N+1 )*INCY + 1 |
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| 78 | DO 10 I = 1, N |
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| 79 | CTEMP = C*CX( IX ) + S*CY( IY ) |
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| 80 | CY( IY ) = C*CY( IY ) - S*CX( IX ) |
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| 81 | CX( IX ) = CTEMP |
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| 82 | IX = IX + INCX |
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| 83 | IY = IY + INCY |
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| 84 | 10 CONTINUE |
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| 85 | RETURN |
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| 86 | * |
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| 87 | * code for both increments equal to 1 |
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| 88 | * |
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| 89 | 20 DO 30 I = 1, N |
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| 90 | CTEMP = C*CX( I ) + S*CY( I ) |
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| 91 | CY( I ) = C*CY( I ) - S*CX( I ) |
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| 92 | CX( I ) = CTEMP |
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| 93 | 30 CONTINUE |
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| 94 | RETURN |
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| 95 | END |
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