LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
dlar2v.f
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00001 *> \brief \b DLAR2V
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
00008 *> \htmlonly
00009 *> Download DLAR2V + dependencies 
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00011 *> [TGZ]</a> 
00012 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlar2v.f"> 
00013 *> [ZIP]</a> 
00014 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlar2v.f"> 
00015 *> [TXT]</a>
00016 *> \endhtmlonly 
00017 *
00018 *  Definition:
00019 *  ===========
00020 *
00021 *       SUBROUTINE DLAR2V( N, X, Y, Z, INCX, C, S, INCC )
00022 * 
00023 *       .. Scalar Arguments ..
00024 *       INTEGER            INCC, INCX, N
00025 *       ..
00026 *       .. Array Arguments ..
00027 *       DOUBLE PRECISION   C( * ), S( * ), X( * ), Y( * ), Z( * )
00028 *       ..
00029 *  
00030 *
00031 *> \par Purpose:
00032 *  =============
00033 *>
00034 *> \verbatim
00035 *>
00036 *> DLAR2V applies a vector of real plane rotations from both sides to
00037 *> a sequence of 2-by-2 real symmetric matrices, defined by the elements
00038 *> of the vectors x, y and z. For i = 1,2,...,n
00039 *>
00040 *>    ( x(i)  z(i) ) := (  c(i)  s(i) ) ( x(i)  z(i) ) ( c(i) -s(i) )
00041 *>    ( z(i)  y(i) )    ( -s(i)  c(i) ) ( z(i)  y(i) ) ( s(i)  c(i) )
00042 *> \endverbatim
00043 *
00044 *  Arguments:
00045 *  ==========
00046 *
00047 *> \param[in] N
00048 *> \verbatim
00049 *>          N is INTEGER
00050 *>          The number of plane rotations to be applied.
00051 *> \endverbatim
00052 *>
00053 *> \param[in,out] X
00054 *> \verbatim
00055 *>          X is DOUBLE PRECISION array,
00056 *>                         dimension (1+(N-1)*INCX)
00057 *>          The vector x.
00058 *> \endverbatim
00059 *>
00060 *> \param[in,out] Y
00061 *> \verbatim
00062 *>          Y is DOUBLE PRECISION array,
00063 *>                         dimension (1+(N-1)*INCX)
00064 *>          The vector y.
00065 *> \endverbatim
00066 *>
00067 *> \param[in,out] Z
00068 *> \verbatim
00069 *>          Z is DOUBLE PRECISION array,
00070 *>                         dimension (1+(N-1)*INCX)
00071 *>          The vector z.
00072 *> \endverbatim
00073 *>
00074 *> \param[in] INCX
00075 *> \verbatim
00076 *>          INCX is INTEGER
00077 *>          The increment between elements of X, Y and Z. INCX > 0.
00078 *> \endverbatim
00079 *>
00080 *> \param[in] C
00081 *> \verbatim
00082 *>          C is DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
00083 *>          The cosines of the plane rotations.
00084 *> \endverbatim
00085 *>
00086 *> \param[in] S
00087 *> \verbatim
00088 *>          S is DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
00089 *>          The sines of the plane rotations.
00090 *> \endverbatim
00091 *>
00092 *> \param[in] INCC
00093 *> \verbatim
00094 *>          INCC is INTEGER
00095 *>          The increment between elements of C and S. INCC > 0.
00096 *> \endverbatim
00097 *
00098 *  Authors:
00099 *  ========
00100 *
00101 *> \author Univ. of Tennessee 
00102 *> \author Univ. of California Berkeley 
00103 *> \author Univ. of Colorado Denver 
00104 *> \author NAG Ltd. 
00105 *
00106 *> \date November 2011
00107 *
00108 *> \ingroup doubleOTHERauxiliary
00109 *
00110 *  =====================================================================
00111       SUBROUTINE DLAR2V( N, X, Y, Z, INCX, C, S, INCC )
00112 *
00113 *  -- LAPACK auxiliary routine (version 3.4.0) --
00114 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00115 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00116 *     November 2011
00117 *
00118 *     .. Scalar Arguments ..
00119       INTEGER            INCC, INCX, N
00120 *     ..
00121 *     .. Array Arguments ..
00122       DOUBLE PRECISION   C( * ), S( * ), X( * ), Y( * ), Z( * )
00123 *     ..
00124 *
00125 *  =====================================================================
00126 *
00127 *     .. Local Scalars ..
00128       INTEGER            I, IC, IX
00129       DOUBLE PRECISION   CI, SI, T1, T2, T3, T4, T5, T6, XI, YI, ZI
00130 *     ..
00131 *     .. Executable Statements ..
00132 *
00133       IX = 1
00134       IC = 1
00135       DO 10 I = 1, N
00136          XI = X( IX )
00137          YI = Y( IX )
00138          ZI = Z( IX )
00139          CI = C( IC )
00140          SI = S( IC )
00141          T1 = SI*ZI
00142          T2 = CI*ZI
00143          T3 = T2 - SI*XI
00144          T4 = T2 + SI*YI
00145          T5 = CI*XI + T1
00146          T6 = CI*YI - T1
00147          X( IX ) = CI*T5 + SI*T4
00148          Y( IX ) = CI*T6 - SI*T3
00149          Z( IX ) = CI*T4 - SI*T5
00150          IX = IX + INCX
00151          IC = IC + INCC
00152    10 CONTINUE
00153 *
00154 *     End of DLAR2V
00155 *
00156       RETURN
00157       END
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