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comparison libcruft/arpack/src/dsconv.f @ 12274:9f5d2ef078e8 release-3-4-x

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import ARPACK sources to libcruft from Debian package libarpack2 2.1+parpack96.dfsg-3+b1
author John W. Eaton <jwe@octave.org>
date Fri, 28 Jan 2011 14:04:33 -0500
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12273:83133b5bf392 12274:9f5d2ef078e8
1 c-----------------------------------------------------------------------
2 c\BeginDoc
3 c
4 c\Name: dsconv
5 c
6 c\Description:
7 c Convergence testing for the symmetric Arnoldi eigenvalue routine.
8 c
9 c\Usage:
10 c call dsconv
11 c ( N, RITZ, BOUNDS, TOL, NCONV )
12 c
13 c\Arguments
14 c N Integer. (INPUT)
15 c Number of Ritz values to check for convergence.
16 c
17 c RITZ Double precision array of length N. (INPUT)
18 c The Ritz values to be checked for convergence.
19 c
20 c BOUNDS Double precision array of length N. (INPUT)
21 c Ritz estimates associated with the Ritz values in RITZ.
22 c
23 c TOL Double precision scalar. (INPUT)
24 c Desired relative accuracy for a Ritz value to be considered
25 c "converged".
26 c
27 c NCONV Integer scalar. (OUTPUT)
28 c Number of "converged" Ritz values.
29 c
30 c\EndDoc
31 c
32 c-----------------------------------------------------------------------
33 c
34 c\BeginLib
35 c
36 c\Routines called:
37 c arscnd ARPACK utility routine for timing.
38 c dlamch LAPACK routine that determines machine constants.
39 c
40 c\Author
41 c Danny Sorensen Phuong Vu
42 c Richard Lehoucq CRPC / Rice University
43 c Dept. of Computational & Houston, Texas
44 c Applied Mathematics
45 c Rice University
46 c Houston, Texas
47 c
48 c\SCCS Information: @(#)
49 c FILE: sconv.F SID: 2.4 DATE OF SID: 4/19/96 RELEASE: 2
50 c
51 c\Remarks
52 c 1. Starting with version 2.4, this routine no longer uses the
53 c Parlett strategy using the gap conditions.
54 c
55 c\EndLib
56 c
57 c-----------------------------------------------------------------------
58 c
59 subroutine dsconv (n, ritz, bounds, tol, nconv)
60 c
61 c %----------------------------------------------------%
62 c | Include files for debugging and timing information |
63 c %----------------------------------------------------%
64 c
65 include 'debug.h'
66 include 'stat.h'
67 c
68 c %------------------%
69 c | Scalar Arguments |
70 c %------------------%
71 c
72 integer n, nconv
73 Double precision
74 & tol
75 c
76 c %-----------------%
77 c | Array Arguments |
78 c %-----------------%
79 c
80 Double precision
81 & ritz(n), bounds(n)
82 c
83 c %---------------%
84 c | Local Scalars |
85 c %---------------%
86 c
87 integer i
88 Double precision
89 & temp, eps23
90 c
91 c %-------------------%
92 c | External routines |
93 c %-------------------%
94 c
95 Double precision
96 & dlamch
97 external dlamch
98
99 c %---------------------%
100 c | Intrinsic Functions |
101 c %---------------------%
102 c
103 intrinsic abs
104 c
105 c %-----------------------%
106 c | Executable Statements |
107 c %-----------------------%
108 c
109 call arscnd (t0)
110 c
111 eps23 = dlamch('Epsilon-Machine')
112 eps23 = eps23**(2.0D+0 / 3.0D+0)
113 c
114 nconv = 0
115 do 10 i = 1, n
116 c
117 c %-----------------------------------------------------%
118 c | The i-th Ritz value is considered "converged" |
119 c | when: bounds(i) .le. TOL*max(eps23, abs(ritz(i))) |
120 c %-----------------------------------------------------%
121 c
122 temp = max( eps23, abs(ritz(i)) )
123 if ( bounds(i) .le. tol*temp ) then
124 nconv = nconv + 1
125 end if
126 c
127 10 continue
128 c
129 call arscnd (t1)
130 tsconv = tsconv + (t1 - t0)
131 c
132 return
133 c
134 c %---------------%
135 c | End of dsconv |
136 c %---------------%
137 c
138 end