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/*
* cluster.c
* cluster_melt
*
* Created by Mark Levy on 21/02/2006.
* Copyright 2006 Centre for Digital Music, Queen Mary, University of London.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*
*/
#include <stdlib.h>
#include "cluster_melt.h"
#define DEFAULT_LAMBDA 0.02;
#define DEFAULT_LIMIT 20;
double kldist(double* a, double* b, int n) {
/* NB assume that all a[i], b[i] are non-negative
because a, b represent probability distributions */
double q, d;
int i;
d = 0;
for (i = 0; i < n; i++)
{
q = (a[i] + b[i]) / 2.0;
if (q > 0)
{
if (a[i] > 0)
d += a[i] * log(a[i] / q);
if (b[i] > 0)
d += b[i] * log(b[i] / q);
}
}
return d;
}
void cluster_melt(double *h, int m, int n, double *Bsched, int t, int k, int l, int *c) {
double lambda, sum, beta, logsumexp, maxlp;
int i, j, a, b, b0, b1, limit, B, it, maxiter, maxiter0, maxiter1;
double** cl; /* reference histograms for each cluster */
int** nc; /* neighbour counts for each histogram */
double** lp; /* soft assignment probs for each histogram */
int* oldc; /* previous hard assignments (to check convergence) */
/* NB h is passed as a 1d row major array */
/* parameter values */
lambda = DEFAULT_LAMBDA;
if (l > 0)
limit = l;
else
limit = DEFAULT_LIMIT; /* use default if no valid neighbourhood limit supplied */
B = 2 * limit + 1;
maxiter0 = 20; /* number of iterations at initial temperature */
maxiter1 = 5; /* number of iterations at subsequent temperatures */
/* allocate memory */
cl = (double**) malloc(k*sizeof(double*));
for (i= 0; i < k; i++)
cl[i] = (double*) malloc(m*sizeof(double));
nc = (int**) malloc(n*sizeof(int*));
for (i= 0; i < n; i++)
nc[i] = (int*) malloc(k*sizeof(int));
lp = (double**) malloc(n*sizeof(double*));
for (i= 0; i < n; i++)
lp[i] = (double*) malloc(k*sizeof(double));
oldc = (int*) malloc(n * sizeof(int));
/* initialise */
for (i = 0; i < k; i++)
{
sum = 0;
for (j = 0; j < m; j++)
{
cl[i][j] = rand(); /* random initial reference histograms */
sum += cl[i][j] * cl[i][j];
}
sum = sqrt(sum);
for (j = 0; j < m; j++)
{
cl[i][j] /= sum; /* normalise */
}
}
//print_array(cl, k, m);
for (i = 0; i < n; i++)
c[i] = 1; /* initially assign all histograms to cluster 1 */
for (a = 0; a < t; a++)
{
beta = Bsched[a];
if (a == 0)
maxiter = maxiter0;
else
maxiter = maxiter1;
for (it = 0; it < maxiter; it++)
{
//if (it == maxiter - 1)
// mexPrintf("hasn't converged after %d iterations\n", maxiter);
for (i = 0; i < n; i++)
{
/* save current hard assignments */
oldc[i] = c[i];
/* calculate soft assignment logprobs for each cluster */
sum = 0;
for (j = 0; j < k; j++)
{
lp[i][ j] = -beta * kldist(cl[j], &h[i*m], m);
/* update matching neighbour counts for this histogram, based on current hard assignments */
/* old version:
nc[i][j] = 0;
if (i >= limit && i <= n - 1 - limit)
{
for (b = i - limit; b <= i + limit; b++)
{
if (c[b] == j+1)
nc[i][j]++;
}
nc[i][j] = B - nc[i][j];
}
*/
b0 = i - limit;
if (b0 < 0)
b0 = 0;
b1 = i + limit;
if (b1 >= n)
b1 = n - 1;
nc[i][j] = b1 - b0 + 1; /* = B except at edges */
for (b = b0; b <= b1; b++)
if (c[b] == j+1)
nc[i][j]--;
sum += exp(lp[i][j]);
}
/* normalise responsibilities and add duration logprior */
logsumexp = log(sum);
for (j = 0; j < k; j++)
lp[i][j] -= logsumexp + lambda * nc[i][j];
}
//print_array(lp, n, k);
/*
for (i = 0; i < n; i++)
{
for (j = 0; j < k; j++)
mexPrintf("%d ", nc[i][j]);
mexPrintf("\n");
}
*/
/* update the assignments now that we know the duration priors
based on the current assignments */
for (i = 0; i < n; i++)
{
maxlp = lp[i][0];
c[i] = 1;
for (j = 1; j < k; j++)
if (lp[i][j] > maxlp)
{
maxlp = lp[i][j];
c[i] = j+1;
}
}
/* break if assignments haven't changed */
i = 0;
while (i < n && oldc[i] == c[i])
i++;
if (i == n)
break;
/* update reference histograms now we know new responsibilities */
for (j = 0; j < k; j++)
{
for (b = 0; b < m; b++)
{
cl[j][b] = 0;
for (i = 0; i < n; i++)
{
cl[j][b] += exp(lp[i][j]) * h[i*m+b];
}
}
sum = 0;
for (i = 0; i < n; i++)
sum += exp(lp[i][j]);
for (b = 0; b < m; b++)
cl[j][b] /= sum; /* normalise */
}
//print_array(cl, k, m);
//mexPrintf("\n\n");
}
}
/* free memory */
for (i = 0; i < k; i++)
free(cl[i]);
free(cl);
for (i = 0; i < n; i++)
free(nc[i]);
free(nc);
for (i = 0; i < n; i++)
free(lp[i]);
free(lp);
free(oldc);
}
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