LAPACK  3.8.0
LAPACK: Linear Algebra PACKage

◆ scnrm2()

real function scnrm2 ( integer  N,
complex, dimension(*)  X,
integer  INCX 
)

SCNRM2

Purpose:
 SCNRM2 returns the euclidean norm of a vector via the function
 name, so that

    SCNRM2 := sqrt( x**H*x )
Parameters
[in]N
          N is INTEGER
         number of elements in input vector(s)
[in]X
          X is COMPLEX array, dimension (N)
         complex vector with N elements
[in]INCX
          INCX is INTEGER
         storage spacing between elements of X
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
November 2017
Further Details:
  -- This version written on 25-October-1982.
     Modified on 14-October-1993 to inline the call to CLASSQ.
     Sven Hammarling, Nag Ltd.

Definition at line 77 of file scnrm2.f.

77 *
78 * -- Reference BLAS level1 routine (version 3.8.0) --
79 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
80 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
81 * November 2017
82 *
83 * .. Scalar Arguments ..
84  INTEGER incx,n
85 * ..
86 * .. Array Arguments ..
87  COMPLEX x(*)
88 * ..
89 *
90 * =====================================================================
91 *
92 * .. Parameters ..
93  REAL one,zero
94  parameter(one=1.0e+0,zero=0.0e+0)
95 * ..
96 * .. Local Scalars ..
97  REAL norm,scale,ssq,temp
98  INTEGER ix
99 * ..
100 * .. Intrinsic Functions ..
101  INTRINSIC abs,aimag,REAL,sqrt
102 * ..
103  IF (n.LT.1 .OR. incx.LT.1) THEN
104  norm = zero
105  ELSE
106  scale = zero
107  ssq = one
108 * The following loop is equivalent to this call to the LAPACK
109 * auxiliary routine:
110 * CALL CLASSQ( N, X, INCX, SCALE, SSQ )
111 *
112  DO 10 ix = 1,1 + (n-1)*incx,incx
113  IF (REAL(x(ix)).NE.zero) then
114  temp = abs(REAL(x(ix)))
115  IF (scale.LT.temp) THEN
116  ssq = one + ssq* (scale/temp)**2
117  scale = temp
118  ELSE
119  ssq = ssq + (temp/scale)**2
120  END IF
121  END IF
122  IF (aimag(x(ix)).NE.zero) THEN
123  temp = abs(aimag(x(ix)))
124  IF (scale.LT.temp) THEN
125  ssq = one + ssq* (scale/temp)**2
126  scale = temp
127  ELSE
128  ssq = ssq + (temp/scale)**2
129  END IF
130  END IF
131  10 CONTINUE
132  norm = scale*sqrt(ssq)
133  END IF
134 *
135  scnrm2 = norm
136  RETURN
137 *
138 * End of SCNRM2.
139 *
real function scnrm2(N, X, INCX)
SCNRM2
Definition: scnrm2.f:77
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