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
|
DOUBLE PRECISION FUNCTION DZNRM2( N, X, INCX )
* .. Scalar Arguments ..
INTEGER INCX, N
* .. Array Arguments ..
COMPLEX*16 X( * )
* ..
*
* DZNRM2 returns the euclidean norm of a vector via the function
* name, so that
*
* DZNRM2 := sqrt( conjg( x' )*x )
*
*
*
* -- This version written on 25-October-1982.
* Modified on 14-October-1993 to inline the call to ZLASSQ.
* Sven Hammarling, Nag Ltd.
*
*
* .. Parameters ..
DOUBLE PRECISION ONE , ZERO
PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
* .. Local Scalars ..
INTEGER IX
DOUBLE PRECISION NORM, SCALE, SSQ, TEMP
* .. Intrinsic Functions ..
INTRINSIC ABS, DIMAG, DBLE, SQRT
* ..
* .. Executable Statements ..
IF( N.LT.1 .OR. INCX.LT.1 )THEN
NORM = ZERO
ELSE
SCALE = ZERO
SSQ = ONE
* The following loop is equivalent to this call to the LAPACK
* auxiliary routine:
* CALL ZLASSQ( N, X, INCX, SCALE, SSQ )
*
DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX
IF( DBLE( X( IX ) ).NE.ZERO )THEN
TEMP = ABS( DBLE( X( IX ) ) )
IF( SCALE.LT.TEMP )THEN
SSQ = ONE + SSQ*( SCALE/TEMP )**2
SCALE = TEMP
ELSE
SSQ = SSQ + ( TEMP/SCALE )**2
END IF
END IF
IF( DIMAG( X( IX ) ).NE.ZERO )THEN
TEMP = ABS( DIMAG( X( IX ) ) )
IF( SCALE.LT.TEMP )THEN
SSQ = ONE + SSQ*( SCALE/TEMP )**2
SCALE = TEMP
ELSE
SSQ = SSQ + ( TEMP/SCALE )**2
END IF
END IF
10 CONTINUE
NORM = SCALE * SQRT( SSQ )
END IF
*
DZNRM2 = NORM
RETURN
*
* End of DZNRM2.
*
END
|
