1 /** @file time_toeplitz.cpp
3 * Calculates determinants of dense symbolic Toeplitz materices.
4 * For 4x4 our matrix would look like this:
5 * [[a,b,a+b,a^2+a*b+b^2], [b,a,b,a+b], [a+b,b,a,b], [a^2+a*b+b^2,a+b,b,a]]
9 * GiNaC Copyright (C) 1999-2004 Johannes Gutenberg University Mainz, Germany
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
28 static unsigned toeplitz_det(unsigned size)
31 const symbol a("a"), b("b");
32 ex p[9] = {ex("a",lst(a,b)),
35 ex("a^2+a*b+b^2",lst(a,b)),
36 ex("a^3+a^2*b-a*b^2+b^3",lst(a,b)),
37 ex("a^4+a^3*b+a^2*b^2+a*b^3+b^4",lst(a,b)),
38 ex("a^5+a^4*b+a^3*b^2-a^2*b^3+a*b^4+b^5",lst(a,b)),
39 ex("a^6+a^5*b+a^4*b^2+a^3*b^3+a^2*b^4+a*b^5+b^6",lst(a,b)),
40 ex("a^7+a^6*b+a^5*b^2+a^4*b^3-a^3*b^4+a^2*b^5+a*b^6+b^7",lst(a,b))
43 // construct Toeplitz matrix (diagonal structure: [[x,y,z],[y,x,y],[z,y,x]]):
45 for (unsigned ro=0; ro<size; ++ro) {
46 for (unsigned nd=ro; nd<size; ++nd) {
47 M.set(nd-ro,nd,p[ro]);
48 M.set(nd,nd-ro,p[ro]);
52 // compute determinant:
53 ex tdet = M.determinant();
55 // dirty consistency check of result:
56 if (!tdet.subs(a==0).subs(b==0).is_zero()) {
57 clog << "Determaint of Toeplitz matrix " << endl
59 << "was miscalculated: det(M)==" << tdet << endl;
66 unsigned time_toeplitz()
70 cout << "timing determinant of polyvariate symbolic Toeplitz matrices" << flush;
71 clog << "-------determinant of polyvariate symbolic Toeplitz matrices:" << endl;
73 vector<unsigned> sizes;
82 for (vector<unsigned>::iterator i=sizes.begin(); i!=sizes.end(); ++i) {
85 result += toeplitz_det(*i);
86 // correct for very small times:
87 while (longines.read()<0.1) {
91 times.push_back(longines.read()/count);
97 clog << "(no output)" << endl;
102 cout << endl << " dim: ";
103 for (vector<unsigned>::iterator i=sizes.begin(); i!=sizes.end(); ++i)
104 cout << '\t' << *i << 'x' << *i;
105 cout << endl << " time/s:";
106 for (vector<double>::iterator i=times.begin(); i!=times.end(); ++i)
107 cout << '\t' << int(1000*(*i))*0.001;