1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
SUBROUTINE ZLASSQ( N, X, INCX, SCALE, SUMSQ )
*
* -- LAPACK auxiliary routine (version 3.1) --
* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
* November 2006
*
* .. Scalar Arguments ..
INTEGER INCX, N
DOUBLE PRECISION SCALE, SUMSQ
* ..
* .. Array Arguments ..
COMPLEX*16 X( * )
* ..
*
* Purpose
* =======
*
* ZLASSQ returns the values scl and ssq such that
*
* ( scl**2 )*ssq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,
*
* where x( i ) = abs( X( 1 + ( i - 1 )*INCX ) ). The value of sumsq is
* assumed to be at least unity and the value of ssq will then satisfy
*
* 1.0 .le. ssq .le. ( sumsq + 2*n ).
*
* scale is assumed to be non-negative and scl returns the value
*
* scl = max( scale, abs( real( x( i ) ) ), abs( aimag( x( i ) ) ) ),
* i
*
* scale and sumsq must be supplied in SCALE and SUMSQ respectively.
* SCALE and SUMSQ are overwritten by scl and ssq respectively.
*
* The routine makes only one pass through the vector X.
*
* Arguments
* =========
*
* N (input) INTEGER
* The number of elements to be used from the vector X.
*
* X (input) COMPLEX*16 array, dimension (N)
* The vector x as described above.
* x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
*
* INCX (input) INTEGER
* The increment between successive values of the vector X.
* INCX > 0.
*
* SCALE (input/output) DOUBLE PRECISION
* On entry, the value scale in the equation above.
* On exit, SCALE is overwritten with the value scl .
*
* SUMSQ (input/output) DOUBLE PRECISION
* On entry, the value sumsq in the equation above.
* On exit, SUMSQ is overwritten with the value ssq .
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D+0 )
* ..
* .. Local Scalars ..
INTEGER IX
DOUBLE PRECISION TEMP1
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, DBLE, DIMAG
* ..
* .. Executable Statements ..
*
IF( N.GT.0 ) THEN
DO 10 IX = 1, 1 + ( N-1 )*INCX, INCX
IF( DBLE( X( IX ) ).NE.ZERO ) THEN
TEMP1 = ABS( DBLE( X( IX ) ) )
IF( SCALE.LT.TEMP1 ) THEN
SUMSQ = 1 + SUMSQ*( SCALE / TEMP1 )**2
SCALE = TEMP1
ELSE
SUMSQ = SUMSQ + ( TEMP1 / SCALE )**2
END IF
END IF
IF( DIMAG( X( IX ) ).NE.ZERO ) THEN
TEMP1 = ABS( DIMAG( X( IX ) ) )
IF( SCALE.LT.TEMP1 ) THEN
SUMSQ = 1 + SUMSQ*( SCALE / TEMP1 )**2
SCALE = TEMP1
ELSE
SUMSQ = SUMSQ + ( TEMP1 / SCALE )**2
END IF
END IF
10 CONTINUE
END IF
*
RETURN
*
* End of ZLASSQ
*
END
|
