- Duh, we had some style discussion again...
[ginac.git] / check / time_vandermonde.cpp
1 /** @file time_vandermonde.cpp
2  *
3  *  Calculates determinants of dense symbolic Vandermonde materices with
4  *  monomials in one single variable as entries.
5  *  For 4x4 our matrix would look like this:
6  *  [[1,a,a^2,a^3], [1,-a,a^2,-a^3], [1,a^2,a^4,a^6], [1,-a^2,a^4,-a^6]]
7  */
8
9 /*
10  *  GiNaC Copyright (C) 1999-2000 Johannes Gutenberg University Mainz, Germany
11  *
12  *  This program is free software; you can redistribute it and/or modify
13  *  it under the terms of the GNU General Public License as published by
14  *  the Free Software Foundation; either version 2 of the License, or
15  *  (at your option) any later version.
16  *
17  *  This program is distributed in the hope that it will be useful,
18  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
19  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20  *  GNU General Public License for more details.
21  *
22  *  You should have received a copy of the GNU General Public License
23  *  along with this program; if not, write to the Free Software
24  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
25  */
26
27 #include "times.h"
28
29 static unsigned vandermonde_det(unsigned size)
30 {
31         unsigned result = 0;
32         symbol a("a");
33         
34         // construct Vandermonde matrix:
35         matrix M(size,size);
36         for (unsigned ro=0; ro<size; ++ro) {
37                 for (unsigned co=0; co<size; ++co) {
38                         if (ro%2)
39                                 M.set(ro,co,pow(-pow(a,1+ro/2),co));
40                         else
41                                 M.set(ro,co,pow(pow(a,1+ro/2),co));
42                 }
43         }
44         
45         // compute determinant:
46         ex vdet = M.determinant();
47         
48         // dirty consistency check of result:
49         if (!vdet.subs(a==1).is_zero()) {
50                 clog << "Determaint of Vandermonde matrix " << endl
51                      << "M==" << M << endl
52                      << "was miscalculated: det(M)==" << vdet << endl;
53                 ++result;
54         }
55         
56         return result;
57 }
58
59 unsigned time_vandermonde(void)
60 {
61         unsigned result = 0;
62         
63         cout << "timing determinant of univariate symbolic Vandermonde matrices" << flush;
64         clog << "-------determinant of univariate symbolic Vandermonde matrices:" << endl;
65         
66         vector<unsigned> sizes;
67         vector<double> times;
68         timer swatch;
69         
70         sizes.push_back(4);
71         sizes.push_back(6);
72         sizes.push_back(8);
73         sizes.push_back(10);
74         
75         for (vector<unsigned>::iterator i=sizes.begin(); i!=sizes.end(); ++i) {
76                 int count = 1;
77                 swatch.start();
78                 result += vandermonde_det(*i);
79                 // correct for very small times:
80                 while (swatch.read()<0.02) {
81                         vandermonde_det(*i);
82                         ++count;
83                 }
84                 times.push_back(swatch.read()/count);
85                 cout << '.' << flush;
86         }
87         
88         if (!result) {
89                 cout << " passed ";
90                 clog << "(no output)" << endl;
91         } else {
92                 cout << " failed ";
93         }
94         // print the report:
95         cout << endl << "       dim:   ";
96         for (vector<unsigned>::iterator i=sizes.begin(); i!=sizes.end(); ++i)
97                 cout << '\t' << *i << 'x' << *i;
98         cout << endl << "       time/s:";
99         for (vector<double>::iterator i=times.begin(); i!=times.end(); ++i)
100                 cout << '\t' << int(1000*(*i))*0.001;
101         cout << endl;
102         
103         return result;
104 }