Add graph references

2026-06-28 13:49:01 +01:00
parent 0a9807e448
commit a11edf0c53
2578 changed files with 868045 additions and 0 deletions
@@ -0,0 +1,187 @@
+/*
+   igraph library.
+   Copyright (C) 2006-2025  The igraph development team <igraph@igraph.org>
+
+   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.
+
+   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 <https://www.gnu.org/licenses/>.
+*/
+
+#include <igraph.h>
+
+#include "test_utilities.h"
+
+
+int main(void) {
+  igraph_t graph;
+
+  igraph_matrix_int_t merges;
+  igraph_vector_t modularity;
+  igraph_vector_int_t membership;
+  igraph_vector_t weights;
+
+  /* Set default seed to get reproducible results */
+  igraph_rng_seed(igraph_rng_default(), 42);
+
+  printf("Basic test\n\n");
+
+  /* Simple unweighted graph */
+  igraph_small(&graph, 3, IGRAPH_UNDIRECTED,
+      0,1, 1,2, 2,0, -1);
+
+  igraph_matrix_int_init(&merges, 0, 0);
+  igraph_vector_init(&modularity, 0);
+  igraph_vector_int_init(&membership, 0);
+
+  igraph_community_walktrap(&graph, NULL, 4, &merges, &modularity, &membership);
+  printf("Merges:\n");
+  print_matrix_int(&merges);
+
+  /* We replace modularity values which are very close to zero
+   * by exact zeros, so that we can have consistent test outputs
+   * across platforms. */
+  printf("Modularity: ");
+  igraph_vector_zapsmall(&modularity, 1e-15);
+  print_vector(&modularity);
+
+  printf("Membership: ");
+  print_vector_int(&membership);
+
+  igraph_vector_int_destroy(&membership);
+  igraph_vector_destroy(&modularity);
+  igraph_matrix_int_destroy(&merges);
+
+  /* Test the case when modularity=NULL and membership=NULL as this caused a crash in
+   * the R interface, see https://github.com/igraph/rigraph/issues/289 */
+
+  printf("\nWithout modularity and membership calculation\n\n");
+
+  igraph_matrix_int_init(&merges, 0, 0);
+
+  igraph_community_walktrap(&graph, NULL, 4, &merges, NULL, NULL);
+  printf("Merges:\n");
+  print_matrix_int(&merges);
+  igraph_matrix_int_destroy(&merges);
+
+  /* Test the case when merges=NULL but modularity is requested,
+   * as the result was previously invalid due to not incrementing
+   * the "merge index" during computation. */
+
+  printf("\nWithout merges matrix calculation\n\n");
+
+  igraph_vector_init(&modularity, 0);
+  igraph_community_walktrap(&graph, NULL, 4, NULL, &modularity, NULL);
+  printf("Modularity:\n");
+  igraph_vector_zapsmall(&modularity, 1e-15);
+  print_vector(&modularity);
+  igraph_vector_destroy(&modularity);
+
+  igraph_destroy(&graph);
+
+  /* Test for bug https://github.com/igraph/igraph/issues/2042 */
+
+  printf("\nBug 2042\n\n");
+
+  igraph_small(&graph, 3, IGRAPH_UNDIRECTED,
+               0,1, -1);
+
+  igraph_matrix_int_init(&merges, 0, 0);
+  igraph_vector_init(&modularity, 0);
+  igraph_vector_int_init(&membership, 0);
+  igraph_vector_init_real(&weights, 1, 0.2);
+
+  igraph_community_walktrap(&graph, &weights, 4, &merges, &modularity, &membership);
+  printf("Merges:\n");
+  print_matrix_int(&merges);
+
+  printf("Modularity: ");
+  igraph_vector_zapsmall(&modularity, 1e-15);
+  print_vector(&modularity);
+
+  printf("Membership: ");
+  print_vector_int(&membership);
+
+  igraph_vector_destroy(&weights);
+  igraph_vector_int_destroy(&membership);
+  igraph_vector_destroy(&modularity);
+  igraph_matrix_int_destroy(&merges);
+
+  igraph_destroy(&graph);
+
+  printf("\nSmall weighted graph\n\n");
+
+  igraph_ring(&graph, 6, IGRAPH_UNDIRECTED, 0, 1);
+
+  igraph_matrix_int_init(&merges, 0, 0);
+  igraph_vector_init(&modularity, 0);
+  igraph_vector_int_init(&membership, 0);
+  igraph_vector_init_real(&weights, 6,
+                          1.0, 0.5, 0.25, 0.75, 1.25, 1.5);
+
+  igraph_community_walktrap(&graph, &weights, 4, &merges, &modularity, &membership);
+  printf("Merges:\n");
+  print_matrix_int(&merges);
+
+  printf("Modularity: ");
+  igraph_vector_zapsmall(&modularity, 1e-15);
+  print_vector(&modularity);
+
+  printf("Membership: ");
+  print_vector_int(&membership);
+
+  /* Negative weights are not allowed */
+  VECTOR(weights)[0] = -0.1;
+  CHECK_ERROR(igraph_community_walktrap(&graph, &weights, 4, &merges, &modularity, &membership), IGRAPH_EINVAL);
+
+  /* Invalid weight vector size */
+  VECTOR(weights)[0] = 0.1;
+  igraph_vector_pop_back(&weights);
+  CHECK_ERROR(igraph_community_walktrap(&graph, &weights, 4, &merges, &modularity, &membership), IGRAPH_EINVAL);
+
+  igraph_vector_destroy(&weights);
+  igraph_vector_int_destroy(&membership);
+  igraph_vector_destroy(&modularity);
+  igraph_matrix_int_destroy(&merges);
+
+  igraph_destroy(&graph);
+
+  printf("\nIsolated vertices\n\n");
+
+  igraph_empty(&graph, 5, IGRAPH_UNDIRECTED);
+
+  igraph_matrix_int_init(&merges, 0, 0);
+  igraph_vector_init(&modularity, 0);
+  igraph_vector_int_init(&membership, 0);
+
+  igraph_community_walktrap(&graph, NULL, 4, &merges, &modularity, &membership);
+  printf("Merges:\n");
+  print_matrix_int(&merges);
+
+  printf("Modularity: ");
+  igraph_vector_zapsmall(&modularity, 1e-15);
+  print_vector(&modularity);
+
+  printf("Membership: ");
+  print_vector_int(&membership);
+
+  igraph_vector_destroy(&weights);
+  igraph_vector_int_destroy(&membership);
+  igraph_vector_destroy(&modularity);
+  igraph_matrix_int_destroy(&merges);
+
+  igraph_destroy(&graph);
+
+
+  VERIFY_FINALLY_STACK();
+
+  return 0;
+}