Annotation of rpl/lapack/lapack/zlacrt.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
! 2: *
! 3: * -- LAPACK auxiliary routine (version 3.2) --
! 4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 6: * November 2006
! 7: *
! 8: * .. Scalar Arguments ..
! 9: INTEGER INCX, INCY, N
! 10: COMPLEX*16 C, S
! 11: * ..
! 12: * .. Array Arguments ..
! 13: COMPLEX*16 CX( * ), CY( * )
! 14: * ..
! 15: *
! 16: * Purpose
! 17: * =======
! 18: *
! 19: * ZLACRT performs the operation
! 20: *
! 21: * ( c s )( x ) ==> ( x )
! 22: * ( -s c )( y ) ( y )
! 23: *
! 24: * where c and s are complex and the vectors x and y are complex.
! 25: *
! 26: * Arguments
! 27: * =========
! 28: *
! 29: * N (input) INTEGER
! 30: * The number of elements in the vectors CX and CY.
! 31: *
! 32: * CX (input/output) COMPLEX*16 array, dimension (N)
! 33: * On input, the vector x.
! 34: * On output, CX is overwritten with c*x + s*y.
! 35: *
! 36: * INCX (input) INTEGER
! 37: * The increment between successive values of CX. INCX <> 0.
! 38: *
! 39: * CY (input/output) COMPLEX*16 array, dimension (N)
! 40: * On input, the vector y.
! 41: * On output, CY is overwritten with -s*x + c*y.
! 42: *
! 43: * INCY (input) INTEGER
! 44: * The increment between successive values of CY. INCY <> 0.
! 45: *
! 46: * C (input) COMPLEX*16
! 47: * S (input) COMPLEX*16
! 48: * C and S define the matrix
! 49: * [ C S ].
! 50: * [ -S C ]
! 51: *
! 52: * =====================================================================
! 53: *
! 54: * .. Local Scalars ..
! 55: INTEGER I, IX, IY
! 56: COMPLEX*16 CTEMP
! 57: * ..
! 58: * .. Executable Statements ..
! 59: *
! 60: IF( N.LE.0 )
! 61: $ RETURN
! 62: IF( INCX.EQ.1 .AND. INCY.EQ.1 )
! 63: $ GO TO 20
! 64: *
! 65: * Code for unequal increments or equal increments not equal to 1
! 66: *
! 67: IX = 1
! 68: IY = 1
! 69: IF( INCX.LT.0 )
! 70: $ IX = ( -N+1 )*INCX + 1
! 71: IF( INCY.LT.0 )
! 72: $ IY = ( -N+1 )*INCY + 1
! 73: DO 10 I = 1, N
! 74: CTEMP = C*CX( IX ) + S*CY( IY )
! 75: CY( IY ) = C*CY( IY ) - S*CX( IX )
! 76: CX( IX ) = CTEMP
! 77: IX = IX + INCX
! 78: IY = IY + INCY
! 79: 10 CONTINUE
! 80: RETURN
! 81: *
! 82: * Code for both increments equal to 1
! 83: *
! 84: 20 CONTINUE
! 85: DO 30 I = 1, N
! 86: CTEMP = C*CX( I ) + S*CY( I )
! 87: CY( I ) = C*CY( I ) - S*CX( I )
! 88: CX( I ) = CTEMP
! 89: 30 CONTINUE
! 90: RETURN
! 91: END
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