Add graph references
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Abdelrahman Said
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/* igraph library.
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Copyright (C) 2022 The igraph development team <igraph@igraph.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <igraph.h>
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#include "test_utilities.h"
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int check_flow(int errorinc,
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const igraph_t *graph, igraph_real_t flow_value,
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const igraph_vector_t *flow, const igraph_vector_int_t *cut,
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const igraph_vector_int_t *partition,
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const igraph_vector_int_t *partition2,
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igraph_int_t source, igraph_int_t target,
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const igraph_vector_t *capacity,
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igraph_bool_t print) {
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igraph_int_t i, n = igraph_vcount(graph), m = igraph_ecount(graph);
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igraph_int_t nc = igraph_vector_int_size(cut);
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igraph_vector_int_t inedges, outedges;
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igraph_bool_t directed = igraph_is_directed(graph);
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igraph_real_t cutsize;
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igraph_t graph_copy;
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igraph_matrix_t sp;
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igraph_vector_int_t cut_int;
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igraph_vector_int_init(&cut_int, 0);
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if (print) {
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printf("flow value: %g\n", (double) flow_value);
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printf("flow: ");
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igraph_vector_print(flow);
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printf("first partition: ");
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igraph_vector_int_print(partition);
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printf("second partition: ");
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igraph_vector_int_print(partition2);
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printf("edges in the cut: ");
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for (i = 0; i < nc; i++) {
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igraph_int_t edge = VECTOR(*cut)[i];
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igraph_int_t from = IGRAPH_FROM(graph, edge);
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igraph_int_t to = IGRAPH_TO (graph, edge);
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if (!directed && from > to) {
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igraph_int_t tmp = from;
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from = to;
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to = tmp;
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}
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printf("%" IGRAPH_PRId "-%" IGRAPH_PRId " (%g), ", from, to, VECTOR(*capacity)[edge]);
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}
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printf("\n");
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}
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fflush(stdout);
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/* Always less than the capacity */
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for (i = 0; i < m; i++) {
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if (VECTOR(*flow)[i] > VECTOR(*capacity)[i]) {
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return errorinc + 3;
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}
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}
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/* What comes in goes out, but only in directed graphs,
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there is no in and out in undirected ones...
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*/
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if (igraph_is_directed(graph)) {
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igraph_vector_int_init(&inedges, 0);
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igraph_vector_int_init(&outedges, 0);
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for (i = 0; i < n; i++) {
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igraph_int_t n1, n2, j;
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igraph_real_t in_flow = 0.0, out_flow = 0.0;
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igraph_incident(graph, &inedges, i, IGRAPH_IN, IGRAPH_LOOPS_ONCE);
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igraph_incident(graph, &outedges, i, IGRAPH_OUT, IGRAPH_LOOPS_ONCE);
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n1 = igraph_vector_int_size(&inedges);
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n2 = igraph_vector_int_size(&outedges);
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for (j = 0; j < n1; j++) {
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igraph_int_t e = VECTOR(inedges)[j];
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in_flow += VECTOR(*flow)[e];
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}
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for (j = 0; j < n2; j++) {
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igraph_int_t e = VECTOR(outedges)[j];
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out_flow += VECTOR(*flow)[e];
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}
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if (i == source) {
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if (in_flow > 0) {
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return errorinc + 4;
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}
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if (out_flow != flow_value) {
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return errorinc + 5;
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}
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} else if (i == target) {
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if (out_flow > 0) {
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return errorinc + 6;
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}
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if (in_flow != flow_value) {
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return errorinc + 7;
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}
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} else {
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if (in_flow != out_flow) {
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return errorinc + 8;
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}
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}
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}
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igraph_vector_int_destroy(&inedges);
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igraph_vector_int_destroy(&outedges);
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}
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/* Check the minimum cut size*/
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for (i = 0, cutsize = 0.0; i < nc; i++) {
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igraph_int_t edge = VECTOR(*cut)[i];
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cutsize += VECTOR(*capacity)[edge];
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}
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if (fabs(cutsize - flow_value) > 1e-14) {
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return errorinc + 9;
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}
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/* Check that the cut indeed cuts */
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igraph_copy(&graph_copy, graph);
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n = igraph_vector_int_size(cut);
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igraph_vector_int_resize(&cut_int, n);
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for (i = 0; i < n; i++) {
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VECTOR(cut_int)[i] = VECTOR(*cut)[i];
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}
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igraph_delete_edges(&graph_copy, igraph_ess_vector(&cut_int));
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igraph_matrix_init(&sp, 1, 1);
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igraph_distances(&graph_copy, NULL, &sp, /*from=*/ igraph_vss_1(source),
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/*to=*/ igraph_vss_1(target), IGRAPH_OUT);
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if (MATRIX(sp, 0, 0) != IGRAPH_INFINITY) {
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return errorinc + 10;
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}
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igraph_matrix_destroy(&sp);
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igraph_destroy(&graph_copy);
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igraph_vector_int_destroy(&cut_int);
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return 0;
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}
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int main(void) {
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igraph_t g;
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igraph_real_t flow_value;
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igraph_vector_int_t cut;
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igraph_vector_t capacity;
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igraph_vector_int_t partition, partition2;
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igraph_vector_t flow;
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igraph_int_t i, n;
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igraph_int_t source, target;
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FILE *infile;
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igraph_real_t flow_value2 = 0.0;
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int check;
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igraph_maxflow_stats_t stats;
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igraph_vector_init(&capacity, 0);
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/***************/
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infile = fopen("ak-4102.max", "r");
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igraph_read_graph_dimacs_flow(
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&g, infile, 0, 0, &source, &target, &capacity, IGRAPH_DIRECTED
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);
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fclose(infile);
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igraph_vector_int_init(&cut, 0);
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igraph_vector_int_init(&partition, 0);
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igraph_vector_int_init(&partition2, 0);
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igraph_vector_init(&flow, 0);
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igraph_maxflow(&g, &flow_value, &flow, &cut, &partition,
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&partition2, source, target, &capacity, &stats);
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if (flow_value != 8207) {
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return 1;
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}
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n = igraph_vector_int_size(&cut);
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for (i = 0; i < n; i++) {
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igraph_int_t e = VECTOR(cut)[i];
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flow_value2 += VECTOR(capacity)[e];
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}
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if (flow_value != flow_value2) {
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return 2;
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}
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/* Check the flow */
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if ( (check = check_flow(0, &g, flow_value, &flow, &cut, &partition,
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&partition2, source, target, &capacity,
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/*print=*/ 0))) {
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return check;
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}
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igraph_destroy(&g);
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igraph_vector_destroy(&capacity);
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igraph_vector_int_destroy(&cut);
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igraph_vector_int_destroy(&partition);
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igraph_vector_int_destroy(&partition2);
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igraph_vector_destroy(&flow);
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/* ------------------------------------- */
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igraph_small(&g, 4, IGRAPH_UNDIRECTED,
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0, 1, 0, 2, 1, 2, 1, 3, 2, 3, -1);
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igraph_vector_init_int_end(&capacity, -1, 4, 2, 10, 2, 2, -1);
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igraph_vector_int_init(&cut, 0);
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igraph_vector_int_init(&partition, 0);
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igraph_vector_int_init(&partition2, 0);
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igraph_vector_init(&flow, 0);
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igraph_maxflow(&g, &flow_value, &flow, &cut, &partition, &partition2,
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/*source=*/ 0, /*target=*/ 3, &capacity, &stats);
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if ( (check = check_flow(20, &g, flow_value, &flow, &cut, &partition,
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&partition2, 0, 3, &capacity,
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/*print=*/ 1))) {
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return check;
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}
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igraph_vector_int_destroy(&cut);
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igraph_vector_int_destroy(&partition2);
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igraph_vector_int_destroy(&partition);
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igraph_vector_destroy(&capacity);
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igraph_vector_destroy(&flow);
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igraph_destroy(&g);
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VERIFY_FINALLY_STACK();
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return 0;
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}
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