media/ffvpx/libavutil/lls.c

   1 /*
   2  * linear least squares model
   3  *
   4  * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   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.
  12  *
  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.
  17  *
  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
  21  */
  22
  23 /**
  24  * @file
  25  * linear least squares model
  26  */
  27
  28 #include <math.h>
  29 #include <string.h>
  30
  31 #include "config.h"
  32 #include "attributes.h"
  33 #include "lls.h"
  34
  35 static void update_lls(LLSModel *m, const double *var)
  36 {
  37     int i, j;
  38
  39     for (i = 0; i <= m->indep_count; i++) {
  40         for (j = i; j <= m->indep_count; j++) {
  41             m->covariance[i][j] += var[i] * var[j];
  42         }
  43     }
  44 }
  45
  46 void avpriv_solve_lls(LLSModel *m, double threshold, unsigned short min_order)
  47 {
  48     int i, j, k;
  49     double (*factor)[MAX_VARS_ALIGN] = (void *) &m->covariance[1][0];
  50     double (*covar) [MAX_VARS_ALIGN] = (void *) &m->covariance[1][1];
  51     double *covar_y                = m->covariance[0];
  52     int count                      = m->indep_count;
  53
  54     for (i = 0; i < count; i++) {
  55         for (j = i; j < count; j++) {
  56             double sum = covar[i][j];
  57
  58             for (k = 0; k <= i-1; k++)
  59                 sum -= factor[i][k] * factor[j][k];
  60
  61             if (i == j) {
  62                 if (sum < threshold)
  63                     sum = 1.0;
  64                 factor[i][i] = sqrt(sum);
  65             } else {
  66                 factor[j][i] = sum / factor[i][i];
  67             }
  68         }
  69     }
  70
  71     for (i = 0; i < count; i++) {
  72         double sum = covar_y[i + 1];
  73
  74         for (k = 0; k <= i-1; k++)
  75             sum -= factor[i][k] * m->coeff[0][k];
  76
  77         m->coeff[0][i] = sum / factor[i][i];
  78     }
  79
  80     for (j = count - 1; j >= min_order; j--) {
  81         for (i = j; i >= 0; i--) {
  82             double sum = m->coeff[0][i];
  83
  84             for (k = i + 1; k <= j; k++)
  85                 sum -= factor[k][i] * m->coeff[j][k];
  86
  87             m->coeff[j][i] = sum / factor[i][i];
  88         }
  89
  90         m->variance[j] = covar_y[0];
  91
  92         for (i = 0; i <= j; i++) {
  93             double sum = m->coeff[j][i] * covar[i][i] - 2 * covar_y[i + 1];
  94
  95             for (k = 0; k < i; k++)
  96                 sum += 2 * m->coeff[j][k] * covar[k][i];
  97
  98             m->variance[j] += m->coeff[j][i] * sum;
  99         }
 100     }
 101 }
 102
 103 static double evaluate_lls(LLSModel *m, const double *param, int order)
 104 {
 105     int i;
 106     double out = 0;
 107
 108     for (i = 0; i <= order; i++)
 109         out += param[i] * m->coeff[order][i];
 110
 111     return out;
 112 }
 113
 114 av_cold void avpriv_init_lls(LLSModel *m, int indep_count)
 115 {
 116     memset(m, 0, sizeof(LLSModel));
 117     m->indep_count = indep_count;
 118     m->update_lls = update_lls;
 119     m->evaluate_lls = evaluate_lls;
 120 #if ARCH_X86
 121     ff_init_lls_x86(m);
 122 #endif
 123 }