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SUBROUTINE <a name="ZLARGV.1"></a><a href="zlargv.f.html#ZLARGV.1">ZLARGV</a>( N, X, INCX, Y, INCY, C, INCC )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> -- LAPACK auxiliary routine (version 3.1) --
</span><span class="comment">*</span><span class="comment"> Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
</span><span class="comment">*</span><span class="comment"> November 2006
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Scalar Arguments ..
</span> INTEGER INCC, INCX, INCY, N
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Array Arguments ..
</span> DOUBLE PRECISION C( * )
COMPLEX*16 X( * ), Y( * )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Purpose
</span><span class="comment">*</span><span class="comment"> =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> <a name="ZLARGV.18"></a><a href="zlargv.f.html#ZLARGV.1">ZLARGV</a> generates a vector of complex plane rotations with real
</span><span class="comment">*</span><span class="comment"> cosines, determined by elements of the complex vectors x and y.
</span><span class="comment">*</span><span class="comment"> For i = 1,2,...,n
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> ( c(i) s(i) ) ( x(i) ) = ( r(i) )
</span><span class="comment">*</span><span class="comment"> ( -conjg(s(i)) c(i) ) ( y(i) ) = ( 0 )
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> where c(i)**2 + ABS(s(i))**2 = 1
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> The following conventions are used (these are the same as in <a name="ZLARTG.27"></a><a href="zlartg.f.html#ZLARTG.1">ZLARTG</a>,
</span><span class="comment">*</span><span class="comment"> but differ from the BLAS1 routine ZROTG):
</span><span class="comment">*</span><span class="comment"> If y(i)=0, then c(i)=1 and s(i)=0.
</span><span class="comment">*</span><span class="comment"> If x(i)=0, then c(i)=0 and s(i) is chosen so that r(i) is real.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Arguments
</span><span class="comment">*</span><span class="comment"> =========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> N (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The number of plane rotations to be generated.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> X (input/output) COMPLEX*16 array, dimension (1+(N-1)*INCX)
</span><span class="comment">*</span><span class="comment"> On entry, the vector x.
</span><span class="comment">*</span><span class="comment"> On exit, x(i) is overwritten by r(i), for i = 1,...,n.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCX (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The increment between elements of X. INCX > 0.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Y (input/output) COMPLEX*16 array, dimension (1+(N-1)*INCY)
</span><span class="comment">*</span><span class="comment"> On entry, the vector y.
</span><span class="comment">*</span><span class="comment"> On exit, the sines of the plane rotations.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCY (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The increment between elements of Y. INCY > 0.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> C (output) DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
</span><span class="comment">*</span><span class="comment"> The cosines of the plane rotations.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCC (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The increment between elements of C. INCC > 0.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Further Details
</span><span class="comment">*</span><span class="comment"> ======= =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> 6-6-96 - Modified with a new algorithm by W. Kahan and J. Demmel
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> This version has a few statements commented out for thread safety
</span><span class="comment">*</span><span class="comment"> (machine parameters are computed on each entry). 10 feb 03, SJH.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Parameters ..
</span> DOUBLE PRECISION TWO, ONE, ZERO
PARAMETER ( TWO = 2.0D+0, ONE = 1.0D+0, ZERO = 0.0D+0 )
COMPLEX*16 CZERO
PARAMETER ( CZERO = ( 0.0D+0, 0.0D+0 ) )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Local Scalars ..
</span><span class="comment">*</span><span class="comment"> LOGICAL FIRST
</span>
INTEGER COUNT, I, IC, IX, IY, J
DOUBLE PRECISION CS, D, DI, DR, EPS, F2, F2S, G2, G2S, SAFMIN,
$ SAFMN2, SAFMX2, SCALE
COMPLEX*16 F, FF, FS, G, GS, R, SN
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Functions ..
</span> DOUBLE PRECISION <a name="DLAMCH.83"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLAPY2.83"></a><a href="dlapy2.f.html#DLAPY2.1">DLAPY2</a>
EXTERNAL <a name="DLAMCH.84"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>, <a name="DLAPY2.84"></a><a href="dlapy2.f.html#DLAPY2.1">DLAPY2</a>
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Intrinsic Functions ..
</span> INTRINSIC ABS, DBLE, DCMPLX, DCONJG, DIMAG, INT, LOG,
$ MAX, SQRT
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Statement Functions ..
</span> DOUBLE PRECISION ABS1, ABSSQ
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Save statement ..
</span><span class="comment">*</span><span class="comment"> SAVE FIRST, SAFMX2, SAFMIN, SAFMN2
</span><span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Data statements ..
</span><span class="comment">*</span><span class="comment"> DATA FIRST / .TRUE. /
</span><span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Statement Function definitions ..
</span> ABS1( FF ) = MAX( ABS( DBLE( FF ) ), ABS( DIMAG( FF ) ) )
ABSSQ( FF ) = DBLE( FF )**2 + DIMAG( FF )**2
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> IF( FIRST ) THEN
</span><span class="comment">*</span><span class="comment"> FIRST = .FALSE.
</span> SAFMIN = <a name="DLAMCH.107"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'S'</span> )
EPS = <a name="DLAMCH.108"></a><a href="dlamch.f.html#DLAMCH.1">DLAMCH</a>( <span class="string">'E'</span> )
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