96 lines
2.6 KiB
FortranFixed
96 lines
2.6 KiB
FortranFixed
SUBROUTINE CSROT( N, CX, INCX, CY, INCY, C, S )
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*
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* .. Scalar Arguments ..
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INTEGER INCX, INCY, N
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REAL C, S
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* ..
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* .. Array Arguments ..
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COMPLEX CX( * ), CY( * )
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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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* CSROT applies a plane rotation, where the cos and sin (c and s) are real
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* and the vectors cx and cy are complex.
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* jack dongarra, linpack, 3/11/78.
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*
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* Arguments
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* ==========
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*
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* N (input) INTEGER
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* On entry, N specifies the order of the vectors cx and cy.
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* N must be at least zero.
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* Unchanged on exit.
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*
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* CX (input) COMPLEX array, dimension at least
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* ( 1 + ( N - 1 )*abs( INCX ) ).
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* Before entry, the incremented array CX must contain the n
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* element vector cx. On exit, CX is overwritten by the updated
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* vector cx.
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*
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* INCX (input) INTEGER
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* On entry, INCX specifies the increment for the elements of
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* CX. INCX must not be zero.
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* Unchanged on exit.
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*
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* CY (input) COMPLEX array, dimension at least
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* ( 1 + ( N - 1 )*abs( INCY ) ).
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* Before entry, the incremented array CY must contain the n
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* element vector cy. On exit, CY is overwritten by the updated
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* vector cy.
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*
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* INCY (input) INTEGER
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* On entry, INCY specifies the increment for the elements of
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* CY. INCY must not be zero.
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* Unchanged on exit.
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*
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* C (input) REAL
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* On entry, C specifies the cosine, cos.
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* Unchanged on exit.
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*
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* S (input) REAL
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* On entry, S specifies the sine, sin.
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* Unchanged on exit.
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, IX, IY
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COMPLEX CTEMP
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* ..
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* .. Executable Statements ..
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*
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IF( N.LE.0 )
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$ RETURN
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IF( INCX.EQ.1 .AND. INCY.EQ.1 )
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$ 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 )
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$ IX = ( -N+1 )*INCX + 1
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IF( INCY.LT.0 )
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$ IY = ( -N+1 )*INCY + 1
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DO 10 I = 1, N
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CTEMP = C*CX( IX ) + S*CY( IY )
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CY( IY ) = C*CY( IY ) - S*CX( IX )
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CX( IX ) = CTEMP
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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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CTEMP = C*CX( I ) + S*CY( I )
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CY( I ) = C*CY( I ) - S*CX( I )
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CX( I ) = CTEMP
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30 CONTINUE
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RETURN
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END
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