2 * linear least squares model
4 * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 * linear least squares model
31 #include "attributes.h"
37 static void update_lls(LLSModel *m, const double *var)
41 for (i = 0; i <= m->indep_count; i++) {
42 for (j = i; j <= m->indep_count; j++) {
43 m->covariance[i][j] += var[i] * var[j];
48 void avpriv_solve_lls(LLSModel *m, double threshold, unsigned short min_order)
51 double (*factor)[MAX_VARS_ALIGN] = (void *) &m->covariance[1][0];
52 double (*covar) [MAX_VARS_ALIGN] = (void *) &m->covariance[1][1];
53 double *covar_y = m->covariance[0];
54 int count = m->indep_count;
56 for (i = 0; i < count; i++) {
57 for (j = i; j < count; j++) {
58 double sum = covar[i][j];
60 for (k = 0; k <= i-1; k++)
61 sum -= factor[i][k] * factor[j][k];
66 factor[i][i] = sqrt(sum);
68 factor[j][i] = sum / factor[i][i];
73 for (i = 0; i < count; i++) {
74 double sum = covar_y[i + 1];
76 for (k = 0; k <= i-1; k++)
77 sum -= factor[i][k] * m->coeff[0][k];
79 m->coeff[0][i] = sum / factor[i][i];
82 for (j = count - 1; j >= min_order; j--) {
83 for (i = j; i >= 0; i--) {
84 double sum = m->coeff[0][i];
86 for (k = i + 1; k <= j; k++)
87 sum -= factor[k][i] * m->coeff[j][k];
89 m->coeff[j][i] = sum / factor[i][i];
92 m->variance[j] = covar_y[0];
94 for (i = 0; i <= j; i++) {
95 double sum = m->coeff[j][i] * covar[i][i] - 2 * covar_y[i + 1];
97 for (k = 0; k < i; k++)
98 sum += 2 * m->coeff[j][k] * covar[k][i];
100 m->variance[j] += m->coeff[j][i] * sum;
105 static double evaluate_lls(LLSModel *m, const double *param, int order)
110 for (i = 0; i <= order; i++)
111 out += param[i] * m->coeff[order][i];
116 av_cold void avpriv_init_lls(LLSModel *m, int indep_count)
118 memset(m, 0, sizeof(LLSModel));
119 m->indep_count = indep_count;
120 m->update_lls = update_lls;
121 m->evaluate_lls = evaluate_lls;
138 av_lfg_init(&lfg, 1);
139 avpriv_init_lls(&m, 3);
141 for (i = 0; i < 100; i++) {
142 LOCAL_ALIGNED(32, double, var, [4]);
145 var[0] = (av_lfg_get(&lfg) / (double) UINT_MAX - 0.5) * 2;
146 var[1] = var[0] + av_lfg_get(&lfg) / (double) UINT_MAX - 0.5;
147 var[2] = var[1] + av_lfg_get(&lfg) / (double) UINT_MAX - 0.5;
148 var[3] = var[2] + av_lfg_get(&lfg) / (double) UINT_MAX - 0.5;
149 m.update_lls(&m, var);
150 avpriv_solve_lls(&m, 0.001, 0);
151 for (order = 0; order < 3; order++) {
152 eval = m.evaluate_lls(&m, var + 1, order);
153 printf("real:%9f order:%d pred:%9f var:%f coeffs:%f %9f %9f\n",
154 var[0], order, eval, sqrt(m.variance[order] / (i + 1)),
155 m.coeff[order][0], m.coeff[order][1],