Annotation of rpl/lapack/lapack/dlargv.f, revision 1.8
1.8 ! bertrand 1: *> \brief \b DLARGV
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: *> \htmlonly
! 9: *> Download DLARGV + dependencies
! 10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlargv.f">
! 11: *> [TGZ]</a>
! 12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlargv.f">
! 13: *> [ZIP]</a>
! 14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlargv.f">
! 15: *> [TXT]</a>
! 16: *> \endhtmlonly
! 17: *
! 18: * Definition:
! 19: * ===========
! 20: *
! 21: * SUBROUTINE DLARGV( N, X, INCX, Y, INCY, C, INCC )
! 22: *
! 23: * .. Scalar Arguments ..
! 24: * INTEGER INCC, INCX, INCY, N
! 25: * ..
! 26: * .. Array Arguments ..
! 27: * DOUBLE PRECISION C( * ), X( * ), Y( * )
! 28: * ..
! 29: *
! 30: *
! 31: *> \par Purpose:
! 32: * =============
! 33: *>
! 34: *> \verbatim
! 35: *>
! 36: *> DLARGV generates a vector of real plane rotations, determined by
! 37: *> elements of the real vectors x and y. For i = 1,2,...,n
! 38: *>
! 39: *> ( c(i) s(i) ) ( x(i) ) = ( a(i) )
! 40: *> ( -s(i) c(i) ) ( y(i) ) = ( 0 )
! 41: *> \endverbatim
! 42: *
! 43: * Arguments:
! 44: * ==========
! 45: *
! 46: *> \param[in] N
! 47: *> \verbatim
! 48: *> N is INTEGER
! 49: *> The number of plane rotations to be generated.
! 50: *> \endverbatim
! 51: *>
! 52: *> \param[in,out] X
! 53: *> \verbatim
! 54: *> X is DOUBLE PRECISION array,
! 55: *> dimension (1+(N-1)*INCX)
! 56: *> On entry, the vector x.
! 57: *> On exit, x(i) is overwritten by a(i), for i = 1,...,n.
! 58: *> \endverbatim
! 59: *>
! 60: *> \param[in] INCX
! 61: *> \verbatim
! 62: *> INCX is INTEGER
! 63: *> The increment between elements of X. INCX > 0.
! 64: *> \endverbatim
! 65: *>
! 66: *> \param[in,out] Y
! 67: *> \verbatim
! 68: *> Y is DOUBLE PRECISION array,
! 69: *> dimension (1+(N-1)*INCY)
! 70: *> On entry, the vector y.
! 71: *> On exit, the sines of the plane rotations.
! 72: *> \endverbatim
! 73: *>
! 74: *> \param[in] INCY
! 75: *> \verbatim
! 76: *> INCY is INTEGER
! 77: *> The increment between elements of Y. INCY > 0.
! 78: *> \endverbatim
! 79: *>
! 80: *> \param[out] C
! 81: *> \verbatim
! 82: *> C is DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
! 83: *> The cosines of the plane rotations.
! 84: *> \endverbatim
! 85: *>
! 86: *> \param[in] INCC
! 87: *> \verbatim
! 88: *> INCC is INTEGER
! 89: *> The increment between elements of C. INCC > 0.
! 90: *> \endverbatim
! 91: *
! 92: * Authors:
! 93: * ========
! 94: *
! 95: *> \author Univ. of Tennessee
! 96: *> \author Univ. of California Berkeley
! 97: *> \author Univ. of Colorado Denver
! 98: *> \author NAG Ltd.
! 99: *
! 100: *> \date November 2011
! 101: *
! 102: *> \ingroup doubleOTHERauxiliary
! 103: *
! 104: * =====================================================================
1.1 bertrand 105: SUBROUTINE DLARGV( N, X, INCX, Y, INCY, C, INCC )
106: *
1.8 ! bertrand 107: * -- LAPACK auxiliary routine (version 3.4.0) --
1.1 bertrand 108: * -- LAPACK is a software package provided by Univ. of Tennessee, --
109: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.8 ! bertrand 110: * November 2011
1.1 bertrand 111: *
112: * .. Scalar Arguments ..
113: INTEGER INCC, INCX, INCY, N
114: * ..
115: * .. Array Arguments ..
116: DOUBLE PRECISION C( * ), X( * ), Y( * )
117: * ..
118: *
119: * =====================================================================
120: *
121: * .. Parameters ..
122: DOUBLE PRECISION ZERO, ONE
123: PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
124: * ..
125: * .. Local Scalars ..
126: INTEGER I, IC, IX, IY
127: DOUBLE PRECISION F, G, T, TT
128: * ..
129: * .. Intrinsic Functions ..
130: INTRINSIC ABS, SQRT
131: * ..
132: * .. Executable Statements ..
133: *
134: IX = 1
135: IY = 1
136: IC = 1
137: DO 10 I = 1, N
138: F = X( IX )
139: G = Y( IY )
140: IF( G.EQ.ZERO ) THEN
141: C( IC ) = ONE
142: ELSE IF( F.EQ.ZERO ) THEN
143: C( IC ) = ZERO
144: Y( IY ) = ONE
145: X( IX ) = G
146: ELSE IF( ABS( F ).GT.ABS( G ) ) THEN
147: T = G / F
148: TT = SQRT( ONE+T*T )
149: C( IC ) = ONE / TT
150: Y( IY ) = T*C( IC )
151: X( IX ) = F*TT
152: ELSE
153: T = F / G
154: TT = SQRT( ONE+T*T )
155: Y( IY ) = ONE / TT
156: C( IC ) = T*Y( IY )
157: X( IX ) = G*TT
158: END IF
159: IC = IC + INCC
160: IY = IY + INCY
161: IX = IX + INCX
162: 10 CONTINUE
163: RETURN
164: *
165: * End of DLARGV
166: *
167: END
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