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+/**
+ * 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 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * (c) Vincenzo Nicosia 2009-2017 -- <v.nicosia@qmul.ac.uk>
+ *
+ * This file is part of NetBunch, a package for complex network
+ * analysis and modelling. For more information please visit:
+ *
+ * http://www.complex-networks.net/
+ *
+ * If you use this software, please add a reference to
+ *
+ * V. Latora, V. Nicosia, G. Russo
+ * "Complex Networks: Principles, Methods and Applications"
+ * Cambridge University Press (2017)
+ * ISBN: 9781107103184
+ *
+ ***********************************************************************
+ *
+ * This program finds the communities in a graph using the
+ * label-propagation algorithm proposed by Raghavan, Albert, and
+ * Kumara.
+ *
+ * References:
+ *
+ * [1] U. N. Raghavan, R. Albert, and S. Kumara. "Near linear time
+ * algorithm to detect community structures in large-scale
+ * networks". Phys. Rev. E 76 (2007), 036106.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <math.h>
+
+
+#include "iltree.h"
+#include "utils.h"
+
+
+typedef struct{
+ int label;
+ int freq;
+} label_freq_t;
+
+#define MODE_SYNC 0x0
+#define MODE_ASYNC 0x1
+
+
+
+/* Usage */
+void usage(char *argv[]){
+ printf("********************************************************************\n"
+ "** **\n"
+ "** -*- label_prop -*- **\n"
+ "** **\n"
+ "** Find the communities in 'graph_in' using the label **\n"
+ "** propagation algorithm. **\n"
+ "** **\n"
+ "** The first parameter is used to choose between synchronous **\n"
+ "** (SYNC) and asynchronous (ASYNC) update. **\n"
+ "** **\n"
+ "** The input file 'graph_in' is an edge-list. **\n"
+ "** If 'graph_in' is equal to '-' (dash), read the file from **\n"
+ "** the standard input (STDIN). **\n"
+ "** **\n"
+ "** If 'max_epochs' is specified, the program stops after **\n"
+ "** 'max_epochs' epochs (useful in conjunction with SYNC, to **\n"
+ "** exit from loops). **\n"
+ "** **\n"
+ "** The program prints on STDOUT the partition obtained when **\n"
+ "** no more label flips are possible, in the format: **\n"
+ "** **\n"
+ "** node_1 comm_1 **\n"
+ "** node_2 comm_2 **\n"
+ "** node_3 comm_3 **\n"
+ "** ..... **\n"
+ "** **\n"
+ "** where 'comm_1' is the community to which 'node_1' belongs. **\n"
+ "** **\n"
+ "** The program prints on STDERR one line for each epoch, **\n"
+ "** in the format: **\n"
+ "** **\n"
+ "** epoch_1 Q_1 flips_1 **\n"
+ "** epoch_2 Q_2 flips_2 **\n"
+ "** ..... **\n"
+ "** **\n"
+ "** where 'epoch_i' is the epoch number, 'Q_i' is the modularity **\n"
+ "** of the partition found at that epoch, and 'flips_i' is the **\n"
+ "** number of label flips occurred in 'epoch_i'. **\n"
+ "** **\n"
+ "********************************************************************\n"
+ " This is Free Software - You can use and distribute it under \n"
+ " the terms of the GNU General Public License, version 3 or later\n\n"
+ " Please visit http://www.complex-networks.net for more information\n\n"
+ " (c) Vincenzo Nicosia 2009-2017 (v.nicosia@qmul.ac.uk)\n"
+ "********************************************************************\n\n"
+ );
+ printf("Usage: %s [SYNC|ASYNC] <graph_in> [<max_epochs>]\n\n" , argv[0]);
+}
+
+
+
+
+/* Compare the frequency of two labels and return a value which allows
+ to sort them in reverse order (i.e., -v, if v=f1-f2) */
+
+int compare_label_freq_reverse(const void *e1, const void *e2){
+
+ label_freq_t v1, v2;
+
+ v1 = *((label_freq_t*)e1);
+ v2 = *((label_freq_t*)e2);
+
+ return - (v1.freq - v2.freq);
+
+}
+
+/* get the most common label in neighs (that is the list of the k
+ neighbours of a node) */
+unsigned int get_most_common_label(unsigned int *neighs, unsigned int k,
+ unsigned int *labels, unsigned int ref_label,
+ int *is_max){
+
+ static label_freq_t *neigh_labels = NULL;
+ static int size = 0;
+ int num, i, j, max_freq;
+
+ if (size < k){
+ size = k;
+ neigh_labels = realloc(neigh_labels, size * sizeof(label_freq_t));
+ }
+
+ neigh_labels[0].label = labels[neighs[0]];
+ neigh_labels[0].freq = 1;
+ num = 1;
+
+ for (i=1; i<k; i ++){
+ for(j=0; j<num; j++){
+ if (labels[neighs[i]] == neigh_labels[j].label)
+ break;
+ }
+ if (j == num){ /* new label */
+ neigh_labels[j].label = labels[neighs[i]];
+ neigh_labels[j].freq = 1;
+ num += 1;
+ }
+ else{/* the label already exists -> increase the counter */
+ neigh_labels[j].freq += 1;
+ }
+ }
+
+ /* Now we sort the array neigh_labels */
+ qsort(neigh_labels, num, sizeof(label_freq_t), compare_label_freq_reverse);
+
+ /* we determine how many neighbours have the maximum freq*/
+ max_freq = neigh_labels[0].freq;
+ i = 1;
+ while(i < num && neigh_labels[i].freq == max_freq){
+ i ++;
+ }
+
+ /* check whether ref_label is one of the most common labels */
+ *is_max = 0;
+ for (j=0; j<i; j++){
+ if (neigh_labels[j].label == ref_label)
+ *is_max = 1;
+ }
+ /* now that we know that there are "i" max_freqs, let's select one
+ of them at random */
+ j = rand() % i;
+
+ return neigh_labels[j].label;
+}
+
+/* reassign the labels so that communities are numbered from 1 to NC */
+int normalise_labels(unsigned int *labels, unsigned int N,
+ unsigned int *label_count){
+
+ unsigned int *label_map;
+ int i, j, num = 0;
+
+
+ label_map = malloc(N * sizeof(unsigned int));
+
+ label_map[0] = labels[0];
+ labels[0] = 0;
+ label_count[0] = 1;
+ num = 1;
+
+ for(i=1; i<N; i ++){
+ for(j=0; j<num; j++){
+ if (labels[i] == label_map[j])
+ break;
+ }
+ if (j == num){
+ label_map[j] = labels[i];
+ label_count[j] = 0;
+ num +=1;
+ }
+ labels[i] = j;
+ label_count[j] += 1;
+ }
+
+ free(label_map);
+ return num;
+}
+
+
+void dump_partition(unsigned int *labels, unsigned int *label_count, unsigned int N){
+
+ int i;
+
+ for(i=0; i<N; i ++){
+ fprintf(stdout, "%d %d\n", i, labels[i]);//, label_count[labels[i]]);
+ }
+}
+
+
+/* compute the modularity of the current partition */
+
+double modularity(unsigned int *J_slap, unsigned int *r_slap, unsigned int N,
+ unsigned int K, unsigned int *comm, unsigned int NC){
+
+ double Q=0;
+ int i, j;
+ unsigned int c_i, c_j;
+ double *pmm, *am;
+
+ pmm = malloc(NC * sizeof(double));
+ am = malloc(NC * sizeof(double));
+
+ for (i=0; i<NC; i++){
+ pmm[i] = am[i] = 0;
+ }
+
+ for(i=0; i<N; i ++){
+ c_i = comm[i];
+ am[c_i] += degree(r_slap, i);
+ for(j=r_slap[i]; j<r_slap[i+1]; j++){
+ c_j = comm[J_slap[j]];
+ if ( c_j == c_i ){
+ pmm[c_i] += 0.5;
+ }
+ }
+ }
+ Q = 0.0;
+ for(i=0; i < NC; i++){
+ Q += (pmm[i]* 2.0 / K - pow((am[i] * 1.0 / K), 2));
+ }
+ free(am);
+ free(pmm);
+ return Q;
+}
+
+
+
+unsigned int* label_propagation(unsigned int *J_slap, unsigned int *r_slap, unsigned int N,
+ unsigned int K, unsigned int *num_epochs,
+ int max_epochs, char mode){
+
+ unsigned int *labels, *next_labels, *tmp_labels, *ids, tmp, new_label;
+ int i, epochs, j, k, cont, is_max;
+ long long int num_flips;
+ double Q;
+
+
+
+ labels = malloc(N * sizeof(unsigned int));
+ ids = malloc(N * sizeof(unsigned int));
+
+ if(mode == MODE_ASYNC){
+ next_labels = labels;
+ }
+ else if (mode == MODE_SYNC){
+ next_labels = malloc(N * sizeof(unsigned int));
+ }
+
+ /* We initialize the list of ids and labels */
+ for (i=0; i<N; i ++){
+ ids[i] = labels[i] = i;
+ }
+
+ cont = 1;
+ epochs = 0;
+ while(cont){
+ if (max_epochs > 0 && epochs > max_epochs)
+ break;
+ cont = 0;
+ if (epochs > 0){
+ Q= modularity(J_slap, r_slap, N, K, labels, N);
+ fprintf(stderr, "%d %g %g\n", epochs, Q, (double)num_flips);
+ }
+ num_flips = 0;
+
+ epochs += 1;
+ for (i=N-1; i>=0; i--){
+ j = rand() % (i+1);
+ tmp = ids[j]; /* This is the id to be considered */
+
+ ids[j] = ids[i];
+ ids[i] = tmp;
+ k = r_slap[tmp + 1] - r_slap[tmp];
+ new_label = get_most_common_label(J_slap+r_slap[tmp], k,labels, labels[tmp], &is_max);
+
+ /* Stop criterion: if the new label is not equal to the
+ old one, continue to another epoch */
+
+ if (mode == MODE_ASYNC && labels[tmp] != new_label){
+ labels[tmp] = new_label;
+ cont = 1;
+ num_flips += 1 ;
+ }
+ if (mode == MODE_SYNC){
+ next_labels[tmp] = new_label;
+ if (labels[tmp] != next_labels[tmp]){
+ cont = 1;
+ num_flips += 1;
+ }
+ }
+ }
+ if (mode == MODE_SYNC){
+ /* Now we can swap labels and next_labels */
+ tmp_labels = labels;
+ labels = next_labels;
+ next_labels = tmp_labels;
+ }
+ }
+ free(ids);
+ *num_epochs = epochs - 1;
+
+ if (mode == MODE_SYNC){
+ free(next_labels);
+ }
+
+ return labels;
+}
+
+
+
+
+
+
+int main(int argc, char *argv[]){
+
+ unsigned int N, K, nc;
+ unsigned int *J_slap, *r_slap, *labels, *label_count, num_epochs, max_epochs;
+ FILE *filein;
+ double Q;
+ char mode;
+
+
+ if (argc < 3){
+ usage(argv);
+ exit(1);
+ }
+
+ srand(time(NULL));
+
+ if (!strcmp(argv[1], "-")){
+ /* take the input from STDIN */
+ filein = stdin;
+ }
+ else {
+ filein = openfile_or_exit(argv[2], "r", 2);
+ }
+
+
+ read_slap(filein, &K, &N, &J_slap, &r_slap);
+
+ fclose(filein);
+
+ if (!my_strcasecmp(argv[1], "sync")){
+ mode = MODE_SYNC;
+ }
+ else{
+ mode = MODE_ASYNC;
+ }
+
+ if (argc > 3)
+ max_epochs = atoi(argv[3]);
+ else
+ max_epochs = 0;
+
+ labels = label_propagation(J_slap, r_slap, N, K, &num_epochs, max_epochs, mode);
+ label_count = malloc(N * sizeof(unsigned int));
+
+ nc = normalise_labels(labels, N, label_count);
+
+ Q= modularity(J_slap, r_slap, N, K, labels, nc);
+
+ printf("### nc: %d Q_max: %f Epochs: %d\n", nc, Q, num_epochs);
+ dump_partition(labels, label_count, N);
+ free(J_slap);
+ free(r_slap);
+ free(label_count);
+ free(labels);
+}
+
+
+
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