92 lines
2.4 KiB
FortranFixed
92 lines
2.4 KiB
FortranFixed
SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
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*
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* -- LAPACK auxiliary routine (version 3.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2006
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*
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* .. Scalar Arguments ..
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INTEGER INCX, INCY, N
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DOUBLE PRECISION C
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COMPLEX*16 S
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* ..
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* .. Array Arguments ..
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COMPLEX*16 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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* ZROT applies a plane rotation, where the cos (C) is real and the
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* sin (S) is complex, and the vectors CX and CY are complex.
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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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* The number of elements in the vectors CX and CY.
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*
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* CX (input/output) COMPLEX*16 array, dimension (N)
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* On input, the vector X.
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* On output, CX is overwritten with C*X + S*Y.
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*
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* INCX (input) INTEGER
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* The increment between successive values of CY. INCX <> 0.
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*
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* CY (input/output) COMPLEX*16 array, dimension (N)
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* On input, the vector Y.
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* On output, CY is overwritten with -CONJG(S)*X + C*Y.
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*
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* INCY (input) INTEGER
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* The increment between successive values of CY. INCX <> 0.
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*
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* C (input) DOUBLE PRECISION
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* S (input) COMPLEX*16
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* C and S define a rotation
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* [ C S ]
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* [ -conjg(S) C ]
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* where C*C + S*CONJG(S) = 1.0.
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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*16 STEMP
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DCONJG
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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 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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STEMP = C*CX( IX ) + S*CY( IY )
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CY( IY ) = C*CY( IY ) - DCONJG( S )*CX( IX )
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CX( IX ) = STEMP
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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 CONTINUE
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DO 30 I = 1, N
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STEMP = C*CX( I ) + S*CY( I )
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CY( I ) = C*CY( I ) - DCONJG( S )*CX( I )
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CX( I ) = STEMP
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30 CONTINUE
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RETURN
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END
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