Annotation of rpl/lapack/lapack/dlarnv.f, revision 1.18
1.11 bertrand 1: *> \brief \b DLARNV returns a vector of random numbers from a uniform or normal distribution.
1.8 bertrand 2: *
3: * =========== DOCUMENTATION ===========
4: *
1.15 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.8 bertrand 7: *
8: *> \htmlonly
1.15 bertrand 9: *> Download DLARNV + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlarnv.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlarnv.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlarnv.f">
1.8 bertrand 15: *> [TXT]</a>
1.15 bertrand 16: *> \endhtmlonly
1.8 bertrand 17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE DLARNV( IDIST, ISEED, N, X )
1.15 bertrand 22: *
1.8 bertrand 23: * .. Scalar Arguments ..
24: * INTEGER IDIST, N
25: * ..
26: * .. Array Arguments ..
27: * INTEGER ISEED( 4 )
28: * DOUBLE PRECISION X( * )
29: * ..
1.15 bertrand 30: *
1.8 bertrand 31: *
32: *> \par Purpose:
33: * =============
34: *>
35: *> \verbatim
36: *>
37: *> DLARNV returns a vector of n random real numbers from a uniform or
38: *> normal distribution.
39: *> \endverbatim
40: *
41: * Arguments:
42: * ==========
43: *
44: *> \param[in] IDIST
45: *> \verbatim
46: *> IDIST is INTEGER
47: *> Specifies the distribution of the random numbers:
48: *> = 1: uniform (0,1)
49: *> = 2: uniform (-1,1)
50: *> = 3: normal (0,1)
51: *> \endverbatim
52: *>
53: *> \param[in,out] ISEED
54: *> \verbatim
55: *> ISEED is INTEGER array, dimension (4)
56: *> On entry, the seed of the random number generator; the array
57: *> elements must be between 0 and 4095, and ISEED(4) must be
58: *> odd.
59: *> On exit, the seed is updated.
60: *> \endverbatim
61: *>
62: *> \param[in] N
63: *> \verbatim
64: *> N is INTEGER
65: *> The number of random numbers to be generated.
66: *> \endverbatim
67: *>
68: *> \param[out] X
69: *> \verbatim
70: *> X is DOUBLE PRECISION array, dimension (N)
71: *> The generated random numbers.
72: *> \endverbatim
73: *
74: * Authors:
75: * ========
76: *
1.15 bertrand 77: *> \author Univ. of Tennessee
78: *> \author Univ. of California Berkeley
79: *> \author Univ. of Colorado Denver
80: *> \author NAG Ltd.
1.8 bertrand 81: *
1.15 bertrand 82: *> \ingroup OTHERauxiliary
1.8 bertrand 83: *
84: *> \par Further Details:
85: * =====================
86: *>
87: *> \verbatim
88: *>
89: *> This routine calls the auxiliary routine DLARUV to generate random
90: *> real numbers from a uniform (0,1) distribution, in batches of up to
91: *> 128 using vectorisable code. The Box-Muller method is used to
92: *> transform numbers from a uniform to a normal distribution.
93: *> \endverbatim
94: *>
95: * =====================================================================
1.1 bertrand 96: SUBROUTINE DLARNV( IDIST, ISEED, N, X )
97: *
1.18 ! bertrand 98: * -- LAPACK auxiliary routine --
1.1 bertrand 99: * -- LAPACK is a software package provided by Univ. of Tennessee, --
100: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
101: *
102: * .. Scalar Arguments ..
103: INTEGER IDIST, N
104: * ..
105: * .. Array Arguments ..
106: INTEGER ISEED( 4 )
107: DOUBLE PRECISION X( * )
108: * ..
109: *
110: * =====================================================================
111: *
112: * .. Parameters ..
113: DOUBLE PRECISION ONE, TWO
114: PARAMETER ( ONE = 1.0D+0, TWO = 2.0D+0 )
115: INTEGER LV
116: PARAMETER ( LV = 128 )
117: DOUBLE PRECISION TWOPI
1.18 ! bertrand 118: PARAMETER ( TWOPI = 6.28318530717958647692528676655900576839D+0 )
1.1 bertrand 119: * ..
120: * .. Local Scalars ..
121: INTEGER I, IL, IL2, IV
122: * ..
123: * .. Local Arrays ..
124: DOUBLE PRECISION U( LV )
125: * ..
126: * .. Intrinsic Functions ..
127: INTRINSIC COS, LOG, MIN, SQRT
128: * ..
129: * .. External Subroutines ..
130: EXTERNAL DLARUV
131: * ..
132: * .. Executable Statements ..
133: *
134: DO 40 IV = 1, N, LV / 2
135: IL = MIN( LV / 2, N-IV+1 )
136: IF( IDIST.EQ.3 ) THEN
137: IL2 = 2*IL
138: ELSE
139: IL2 = IL
140: END IF
141: *
142: * Call DLARUV to generate IL2 numbers from a uniform (0,1)
143: * distribution (IL2 <= LV)
144: *
145: CALL DLARUV( ISEED, IL2, U )
146: *
147: IF( IDIST.EQ.1 ) THEN
148: *
149: * Copy generated numbers
150: *
151: DO 10 I = 1, IL
152: X( IV+I-1 ) = U( I )
153: 10 CONTINUE
154: ELSE IF( IDIST.EQ.2 ) THEN
155: *
156: * Convert generated numbers to uniform (-1,1) distribution
157: *
158: DO 20 I = 1, IL
159: X( IV+I-1 ) = TWO*U( I ) - ONE
160: 20 CONTINUE
161: ELSE IF( IDIST.EQ.3 ) THEN
162: *
163: * Convert generated numbers to normal (0,1) distribution
164: *
165: DO 30 I = 1, IL
166: X( IV+I-1 ) = SQRT( -TWO*LOG( U( 2*I-1 ) ) )*
167: $ COS( TWOPI*U( 2*I ) )
168: 30 CONTINUE
169: END IF
170: 40 CONTINUE
171: RETURN
172: *
173: * End of DLARNV
174: *
175: END
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