LAPACK 3.12.0 LAPACK: Linear Algebra PACKage
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 subroutine dladiv ( double precision a, double precision b, double precision c, double precision d, double precision p, double precision q )

DLADIV performs complex division in real arithmetic, avoiding unnecessary overflow.

Purpose:
``` DLADIV performs complex division in  real arithmetic

a + i*b
p + i*q = ---------
c + i*d

The algorithm is due to Michael Baudin and Robert L. Smith
and can be found in the paper
"A Robust Complex Division in Scilab"```
Parameters
 [in] A ` A is DOUBLE PRECISION` [in] B ` B is DOUBLE PRECISION` [in] C ` C is DOUBLE PRECISION` [in] D ``` D is DOUBLE PRECISION The scalars a, b, c, and d in the above expression.``` [out] P ` P is DOUBLE PRECISION` [out] Q ``` Q is DOUBLE PRECISION The scalars p and q in the above expression.```

Definition at line 90 of file dladiv.f.

91*
92* -- LAPACK auxiliary routine --
93* -- LAPACK is a software package provided by Univ. of Tennessee, --
94* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
95*
96* .. Scalar Arguments ..
97 DOUBLE PRECISION A, B, C, D, P, Q
98* ..
99*
100* =====================================================================
101*
102* .. Parameters ..
103 DOUBLE PRECISION BS
104 parameter( bs = 2.0d0 )
105 DOUBLE PRECISION HALF
106 parameter( half = 0.5d0 )
107 DOUBLE PRECISION TWO
108 parameter( two = 2.0d0 )
109*
110* .. Local Scalars ..
111 DOUBLE PRECISION AA, BB, CC, DD, AB, CD, S, OV, UN, BE, EPS
112* ..
113* .. External Functions ..
114 DOUBLE PRECISION DLAMCH
115 EXTERNAL dlamch
116* ..
117* .. External Subroutines ..
119* ..
120* .. Intrinsic Functions ..
121 INTRINSIC abs, max
122* ..
123* .. Executable Statements ..
124*
125 aa = a
126 bb = b
127 cc = c
128 dd = d
129 ab = max( abs(a), abs(b) )
130 cd = max( abs(c), abs(d) )
131 s = 1.0d0
132
133 ov = dlamch( 'Overflow threshold' )
134 un = dlamch( 'Safe minimum' )
135 eps = dlamch( 'Epsilon' )
136 be = bs / (eps*eps)
137
138 IF( ab >= half*ov ) THEN
139 aa = half * aa
140 bb = half * bb
141 s = two * s
142 END IF
143 IF( cd >= half*ov ) THEN
144 cc = half * cc
145 dd = half * dd
146 s = half * s
147 END IF
148 IF( ab <= un*bs/eps ) THEN
149 aa = aa * be
150 bb = bb * be
151 s = s / be
152 END IF
153 IF( cd <= un*bs/eps ) THEN
154 cc = cc * be
155 dd = dd * be
156 s = s * be
157 END IF
158 IF( abs( d ).LE.abs( c ) ) THEN
159 CALL dladiv1(aa, bb, cc, dd, p, q)
160 ELSE
161 CALL dladiv1(bb, aa, dd, cc, p, q)
162 q = -q
163 END IF
164 p = p * s
165 q = q * s
166*
167 RETURN
168*