Implement max flow algorithm

src/flow.c

@@ -0,0 +1,154 @@
+#include <malloc.h>
+#include <float.h>
+#include "gtsp.h"
+#include "flow.h"
+#include "util.h"
+
+int flow_find_max_flow(
+        const struct Graph *digraph,
+        const double *capacities,
+        struct Node *from,
+        struct Node *to,
+        double *flow,
+        double *value)
+{
+    int rval = 0;
+
+    int path_length;
+    struct Edge **path_edges = 0;
+    double path_capacity;
+
+    double *residual_caps = 0;
+
+    residual_caps = (double *) malloc(digraph->edge_count * sizeof(double));
+    abort_if(!residual_caps, "could not allocate residual_caps");
+
+    path_edges = (struct Edge **) malloc(
+            digraph->edge_count * sizeof(struct Edge *));
+    abort_if(!path_edges, "could not allocate path_edges");
+
+    for (int i = 0; i < digraph->edge_count; i++)
+    {
+        flow[i] = 0;
+        residual_caps[i] = capacities[i];
+        abort_if(!digraph->edges[i].reverse,
+                "digraph must have reverse edge information");
+    }
+
+    *value = 0;
+
+    while (1)
+    {
+        flow_find_augmenting_path(digraph, residual_caps, from, to,
+                &path_length, path_edges, &path_capacity);
+
+        if (path_length == 0) break;
+
+        (*value) += path_capacity;
+
+        for (int i = 0; i < path_length; i++)
+        {
+            struct Edge *e = &digraph->edges[path_edges[i]->index];
+
+            residual_caps[e->index] -= path_capacity;
+            residual_caps[e->reverse->index] += path_capacity;
+
+            flow[e->index] += path_capacity;
+            flow[e->reverse->index] -= path_capacity;
+        }
+    }
+
+    CLEANUP:
+    if (path_edges) free(path_edges);
+    if (residual_caps) free(residual_caps);
+    return rval;
+}
+
+int flow_find_augmenting_path(
+        const struct Graph *graph,
+        const double *residual_caps,
+        struct Node *from,
+        struct Node *to,
+        int *path_length,
+        struct Edge **path_edges,
+        double *path_capacity)
+{
+    int rval = 0;
+
+    struct Node **queue = 0;
+    int queue_start = 0;
+    int queue_end = 0;
+
+    struct Node **parents = 0;
+    struct Edge **parent_edges = 0;
+
+    int node_count = graph->node_count;
+
+    queue = (struct Node **) malloc(node_count * sizeof(struct Node *));
+    parents = (struct Node **) malloc(node_count * sizeof(struct Node *));
+    parent_edges = (struct Edge **) malloc(node_count * sizeof(struct Edge *));
+
+    abort_if(!queue, "could not allocate queue");
+    abort_if(!parents, "could not allocate parents");
+    abort_if(!parent_edges, "could not allocate parent_edges");
+
+    for (int i = 0; i < node_count; i++)
+        graph->nodes[i].mark = 0;
+
+    int found = 0;
+    queue[queue_end++] = from;
+
+    while (queue_end > queue_start)
+    {
+        struct Node *n = queue[queue_start++];
+
+        n->mark = 2;
+
+        for (int i = 0; i < n->degree; i++)
+        {
+            struct Node *neighbor = n->adj[i].neighbor;
+            struct Edge *edge = n->adj[i].edge;
+
+            if (neighbor->mark > 0) continue;
+            if (residual_caps[edge->index] < LP_EPSILON) continue;
+
+            parents[neighbor->index] = n;
+            parent_edges[neighbor->index] = edge;
+
+            queue[queue_end++] = neighbor;
+            neighbor->mark = 1;
+
+            if (neighbor == to)
+            {
+                found = 1;
+                break;
+            }
+        }
+
+        if (found) break;
+    }
+
+    *path_length = 0;
+    *path_capacity = DBL_MAX;
+
+    if (queue_end == queue_start) goto CLEANUP;
+
+    struct Node *n = to;
+    while (n != from)
+    {
+        struct Edge *edge = parent_edges[n->index];
+        path_edges[*path_length] = edge;
+
+        double c = residual_caps[edge->index];
+        if (c < *path_capacity) *path_capacity = c;
+
+        n = parents[n->index];
+        (*path_length)++;
+    }
+
+    CLEANUP:
+    if (parents) free(parents);
+    if (parent_edges) free(parent_edges);
+    if (queue) free(queue);
+    return rval;
+}

src/flow.h

@@ -0,0 +1,27 @@
+//
+// Created by isoron on 19/03/15.
+//
+
+#ifndef _PROJECT_FLOW_H_
+#define _PROJECT_FLOW_H_
+
+int flow_find_augmenting_path(
+        const struct Graph *graph,
+        const double *residual_caps,
+        struct Node *from,
+        struct Node *to,
+        int *path_length,
+        struct Edge **path_edges,
+        double *path_capacity);
+
+int flow_find_max_flow(
+        const struct Graph *digraph,
+        const double *capacities,
+        struct Node *from,
+        struct Node *to,
+        double *flow,
+        double *value);
+
+#include "graph.h"
+
+#endif //_PROJECT_FLOW_H_

src/graph.c

@@ -1,103 +1,159 @@
 #include <malloc.h>
-#include "main.h"
 #include "graph.h"
 #include "util.h"
 #include "lp.h"
 
-void graph_dfs(
+void graph_init(struct Graph *graph)
-        int n, struct Graph *G, double *x, int *island_size, int *island_nodes)
-{
-    *(island_nodes + (*island_size)) = n;
-    (*island_size)++;
-
-    struct Node *pn = &G->node_list[n];
-    pn->mark = 1;
-
-    for (int i = 0; i < pn->deg; i++)
-    {
-        if (x[pn->adj[i].e] > LP_EPSILON)
-        {
-            int neighbor = pn->adj[i].n;
-
-            if (G->node_list[neighbor].mark == 0)
-                graph_dfs(neighbor, G, x, island_size, island_nodes);
-        }
-    }
-}
-
-void graph_init(struct Graph *G)
 {
-    if (!G) return;
+    if (!graph) return;
 
-    G->node_list = 0;
+    graph->nodes = 0;
-    G->adj_space = 0;
+    graph->adj = 0;
-    G->node_count = 0;
+    graph->node_count = 0;
-    G->edge_count = 0;
+    graph->edge_count = 0;
 }
 
-void graph_free(struct Graph *G)
+void graph_free(struct Graph *graph)
 {
-    if (!G) return;
+    if (!graph) return;
 
-    if (G->node_list) free(G->node_list);
+    if (graph->nodes) free(graph->nodes);
-    if (G->adj_space) free(G->adj_space);
+    if (graph->adj) free(graph->adj);
 }
 
-int graph_build(int node_count, int edge_count, int *edge_list, struct Graph *G)
+int graph_build(
+        int node_count,
+        int edge_count,
+        int *edges,
+        int is_directed,
+        struct Graph *graph)
 {
     int rval = 0;
     struct Node *n;
-    struct AdjObj *p;
+    struct Adjacency *p;
 
-    G->node_list = (struct Node *) malloc(node_count * sizeof(struct Node));
+    graph->edges = (struct Edge *) malloc(edge_count * sizeof(struct Edge));
-    G->adj_space =
+    graph->nodes = (struct Node *) malloc(node_count * sizeof(struct Node));
-            (struct AdjObj *) malloc(2 * edge_count * sizeof(struct AdjObj));
+    graph->adj = (struct Adjacency *) malloc(
+            2 * edge_count * sizeof(struct Adjacency));
 
-    abort_if(!G->node_list, "could not allocate G->node_list");
+    abort_if(!graph->edges, "could not allocate G->edges\n");
-    abort_if(!G->adj_space, "could not allocate G->adj_space");
+    abort_if(!graph->nodes, "could not allocate G->nodes");
+    abort_if(!graph->adj, "could not allocate G->adj");
 
     for (int i = 0; i < node_count; i++)
-        G->node_list[i].deg = 0;
+    {
+        graph->nodes[i].index = i;
+        graph->nodes[i].degree = 0;
+    }
 
     for (int i = 0; i < edge_count; i++)
     {
-        int a = edge_list[2 * i];
+        int a = edges[2 * i];
-        int b = edge_list[2 * i + 1];
+        int b = edges[2 * i + 1];
-        G->node_list[a].deg++;
+        graph->nodes[a].degree++;
-        G->node_list[b].deg++;
+        if(!is_directed) graph->nodes[b].degree++;
+
+        graph->edges[i].reverse = 0;
+        graph->edges[i].index = i;
+        graph->edges[i].from = &graph->nodes[a];
+        graph->edges[i].to = &graph->nodes[b];
     }
 
-    p = G->adj_space;
+    p = graph->adj;
     for (int i = 0; i < node_count; i++)
     {
-        G->node_list[i].adj = p;
+        graph->nodes[i].adj = p;
-        p += G->node_list[i].deg;
+        p += graph->nodes[i].degree;
-        G->node_list[i].deg = 0;
+        graph->nodes[i].degree = 0;
     }
 
     for (int i = 0; i < edge_count; i++)
     {
-        int a = edge_list[2 * i];
+        int a = edges[2 * i];
-        int b = edge_list[2 * i + 1];
+        int b = edges[2 * i + 1];
-        n = &G->node_list[a];
+
-        n->adj[n->deg].n = b;
+        n = &graph->nodes[a];
-        n->adj[n->deg].e = i;
+        n->adj[n->degree].neighbor_index = b;
-        n->deg++;
+        n->adj[n->degree].edge_index = i;
-        n = &G->node_list[b];
+        n->adj[n->degree].neighbor = &graph->nodes[b];
-        n->adj[n->deg].n = a;
+        n->adj[n->degree].edge = &graph->edges[i];
-        n->adj[n->deg].e = i;
+        n->degree++;
-        n->deg++;
+
+        if(!is_directed)
+        {
+            n = &graph->nodes[b];
+            n->adj[n->degree].neighbor_index = a;
+            n->adj[n->degree].edge_index = i;
+            n->adj[n->degree].neighbor = &graph->nodes[b];
+            n->adj[n->degree].edge = &graph->edges[i];
+            n->degree++;
+        }
     }
 
-    G->node_count = node_count;
+    graph->node_count = node_count;
-    G->edge_count = edge_count;
+    graph->edge_count = edge_count;
 
     CLEANUP:
     if (rval)
     {
-        if (G->node_list) free(G->node_list);
+        if (graph->edges) free(graph->edges);
-        if (G->adj_space) free(G->adj_space);
+        if (graph->nodes) free(graph->nodes);
+        if (graph->adj) free(graph->adj);
+    }
+    return rval;
+}
+
+void graph_dfs(
+        int n, struct Graph *G, double *x, int *island_size, int *island_nodes)
+{
+    *(island_nodes + (*island_size)) = n;
+    (*island_size)++;
+
+    struct Node *pn = &G->nodes[n];
+    pn->mark = 1;
+
+    for (int i = 0; i < pn->degree; i++)
+    {
+        if (x[pn->adj[i].edge_index] > LP_EPSILON)
+        {
+            int neighbor = pn->adj[i].neighbor_index;
+
+            if (G->nodes[neighbor].mark == 0)
+                graph_dfs(neighbor, G, x, island_size, island_nodes);
+        }
+    }
+}
+
+int graph_build_directed_from_undirected(
+        const struct Graph *graph, struct Graph *digraph)
+{
+    int rval = 0;
+
+    int *edges = 0;
+
+    edges = (int *) malloc(4 * graph->edge_count * sizeof(int));
+    abort_if(!edges, "could not allocate edges");
+
+    for (int i = 0; i < graph->edge_count; i++)
+    {
+        struct Edge *e = &graph->edges[i];
+        edges[4 * i] = edges[4 * i + 3] = e->from->index;
+        edges[4 * i + 1] = edges[4 * i + 2] = e->to->index;
     }
+
+    rval = graph_build(graph->node_count, 2 * graph->edge_count, edges, 1,
+            digraph);
+    abort_if(rval, "graph_build failed");
+
+    for (int i = 0; i < graph->edge_count; i++)
+    {
+        digraph->edges[2 * i].reverse = &digraph->edges[i * 2 + 1];
+        digraph->edges[2 * i + 1].reverse = &digraph->edges[i * 2];
+    }
+
+    CLEANUP:
+    if (!edges) free(edges);
     return rval;
 }
 

src/graph.h

@@ -3,39 +3,60 @@
 
 #include "main.h"
 
-struct AdjObj
+struct Adjacency
 {
-    /* Index of neighbor node */
+    int edge_index;
-    int n;
+    int neighbor_index;
 
-    /* Index of adj joining neighbor */
+    struct Edge *edge;
-    int e;
+    struct Node *neighbor;
 };
 
 struct Node
 {
-    int deg;
-    struct AdjObj *adj;
     int mark;
+
+    int index;
+    int degree;
+
+    struct Adjacency *adj;
+};
+
+struct Edge
+{
+    int index;
+    int weight;
+
+    struct Node *from;
+    struct Node *to;
+
+    struct Edge *reverse;
 };
 
 struct Graph
 {
     int node_count;
     int edge_count;
-    struct Node *node_list;
+
-    struct AdjObj *adj_space;
+    struct Edge *edges;
+    struct Node *nodes;
+
+    struct Adjacency *adj;
 };
 
 void graph_dfs(
         int n, struct Graph *G, double *x, int *icount, int *island);
 
-void graph_init(struct Graph *G);
+void graph_init(struct Graph *graph);
 
-void graph_free(struct Graph *G);
+void graph_free(struct Graph *graph);
 
-int graph_build
+int graph_build(
-        (int node_count, int edge_count, int *edge_list, struct Graph *G);
+        int node_count,
+        int edge_count,
+        int *edges,
+        int is_directed,
+        struct Graph *graph);
 
 void get_delta(
         int nsize,
@@ -46,4 +67,7 @@ void get_delta(
         int *delta,
         int *marks);
 
+int graph_build_directed_from_undirected
+        (const struct Graph *graph, struct Graph *digraph);
+
 #endif

src/gtsp.c

@@ -6,20 +6,19 @@
 
 int GTSP_init_data(struct GTSP *data)
 {
-    data->node_count = 0;
-    data->edge_count = 0;
-    data->edges = 0;
     data->clusters = 0;
     data->cluster_count = 0;
     data->x_coordinates = 0;
     data->y_coordinates = 0;
+    graph_init(data->graph);
+
     return 0;
 }
 
 void GTSP_free(struct GTSP *data)
 {
     if (!data) return;
-    if (data->edges) free(data->edges);
+    if (data->graph) graph_free(data->graph);
     if (data->clusters) free(data->clusters);
     if (data->x_coordinates) free(data->x_coordinates);
     if (data->y_coordinates) free(data->y_coordinates);
@@ -30,21 +29,33 @@ int GTSP_create_random_problem(
 {
     int rval = 0;
 
-    struct Edge *edges = 0;
+    int *edges = 0;
+    int *weights = 0;
     int *clusters = 0;
 
     double *x_coords = 0;
     double *y_coords = 0;
 
+    struct Graph *graph = 0;
+
     int edge_count = (node_count * (node_count - 1)) / 2;
 
-    edges = (struct Edge *) malloc(edge_count * sizeof(struct Edge));
+    graph = (struct Graph*) malloc(sizeof(struct Graph));
+    abort_if(!graph, "could not allocate graph\n");
+
+    graph_init(graph);
+
+    edges = (int *) malloc(2 * edge_count * sizeof(int));
+    weights = (int *) malloc(edge_count * sizeof(int));
     clusters = (int *) malloc(node_count * sizeof(int));
+
     abort_if(!edges, "could not allocate data->edges\n");
+    abort_if(!weights, "could not allocate weights\n");
     abort_if(!clusters, "could not allocate clusters\n");
 
     x_coords = (double *) malloc(node_count * sizeof(double));
     y_coords = (double *) malloc(node_count * sizeof(double));
+
     abort_if(!x_coords, "could not allocate x_coords\n");
     abort_if(!y_coords, "could not allocate y_coords\n");
 
@@ -52,21 +63,22 @@ int GTSP_create_random_problem(
             x_coords, y_coords, clusters);
     abort_if(rval, "generate_random_clusters_2d failed");
 
-    int current_edge = 0;
+    int curr_edge = 0;
     for (int i = 0; i < edge_count; i++)
         for (int j = i + 1; j < node_count; j++)
         {
-            edges[current_edge].from = i;
+            edges[curr_edge * 2] = i;
-            edges[current_edge].to = j;
+            edges[curr_edge * 2 + 1] = j;
-            edges[current_edge].weight =
+            weights[curr_edge] =
                     get_euclidean_distance(x_coords, y_coords, i, j);
 
-            current_edge++;
+            curr_edge++;
         }
 
-    data->node_count = node_count;
+    rval = graph_build(node_count, edge_count, edges, 0, graph);
-    data->edge_count = edge_count;
+    abort_if(rval, "graph_build failed");
-    data->edges = edges;
+
+    data->graph = graph;
     data->clusters = clusters;
     data->cluster_count = cluster_count;
     data->x_coordinates = x_coords;
@@ -85,11 +97,11 @@ int GTSP_init_lp(struct LP *lp, struct GTSP *data)
 {
     int rval = 0;
 
-    int node_count = data->node_count;
+    int node_count = data->graph->node_count;
-    int edge_count = data->edge_count;
+    int edge_count = data->graph->edge_count;
     int cluster_count = data->cluster_count;
     int *clusters = data->clusters;
-    struct Edge *edges = data->edges;
+    struct Edge *edges = data->graph->edges;
 
     for (int i = 0; i < node_count; i++)
     {
@@ -122,7 +134,7 @@ int GTSP_init_lp(struct LP *lp, struct GTSP *data)
     {
         double obj = (double) edges[i].weight;
         double cmatval[] = {1.0, 1.0};
-        int cmatind[] = {edges[i].from, edges[i].to};
+        int cmatind[] = {edges[i].from->index, edges[i].to->index};
 
         rval = LP_add_cols(lp, 1, 2, &obj, &cmatbeg, cmatind, cmatval, &lb,
                 &ub);
@@ -142,9 +154,9 @@ int GTSP_write_data(struct GTSP *data, char *filename)
     file = fopen(filename, "w");
     abort_if(!file, "could not open file");
 
-    fprintf(file, "%d %d\n", data->node_count, data->cluster_count);
+    fprintf(file, "%d %d\n", data->graph->node_count, data->cluster_count);
 
-    for (int i = 0; i < data->node_count; i++)
+    for (int i = 0; i < data->graph->node_count; i++)
     {
         fprintf(file, "%.2lf %.2lf %d\n", data->x_coordinates[i],
                 data->y_coordinates[i], data->clusters[i]);
@@ -159,25 +171,27 @@ int GTSP_write_solution(struct GTSP *data, char *filename, double *x)
 {
     int rval = 0;
 
-    struct Edge *edges = data->edges;
+    struct Edge *edges = data->graph->edges;
-    int node_count = data->node_count;
+    int node_count = data->graph->node_count;
+    int edge_count = data->graph->edge_count;
 
     FILE *file;
     file = fopen(filename, "w");
     abort_if(!file, "could not open file");
 
     int positive_edge_count = 0;
-    for (int i = 0; i < data->edge_count; i++)
+    for (int i = 0; i < edge_count; i++)
         if (x[i + node_count] > 0.5)
             positive_edge_count++;
 
     fprintf(file, "%d\n", positive_edge_count);
 
-    for (int i = 0; i < data->edge_count; i++)
+    for (int i = 0; i < edge_count; i++)
         if (x[i + node_count] > 0.5)
-            fprintf(file, "%d %d\n", edges[i].from, edges[i].to);
+            fprintf(file, "%d %d\n", edges[i].from->index, edges[i].to->index);
 
     CLEANUP:
     if (file) fclose(file);
     return rval;
 }
+

src/gtsp.h

@@ -6,19 +6,11 @@
 #define _PROJECT_GTSP_H_
 
 #include "lp.h"
-
+#include "graph.h"
-struct Edge
-{
-    int from;
-    int to;
-    int weight;
-};
 
 struct GTSP
 {
-    int node_count;
+    struct Graph *graph;
-    int edge_count;
-    struct Edge *edges;
 
     int *clusters;
     int cluster_count;

src/main.c

@@ -8,6 +8,7 @@
 #include "tsp.h"
 #include "branch_and_cut.h"
 #include "gtsp.h"
+#include "flow.h"
 
 char *INPUT_FILENAME = 0;
 unsigned int SEED = 0;
@@ -19,6 +20,79 @@ static int parse_arguments_tsp(int ac, char **av);
 
 static void print_usage_tsp(char *f);
 
+int test_max_flow()
+{
+    int rval = 0;
+
+    int *edges = 0;
+    double *capacities = 0;
+    double *flow = 0;
+    double flow_value;
+
+    FILE *f = fopen("tmp/flow.in", "r");
+    abort_if(!f, "could not open input file");
+
+    struct Graph graph;
+    graph_init(&graph);
+
+    int node_count, edge_count;
+
+    rval = fscanf(f, "%d %d ", &node_count, &edge_count);
+    abort_if(rval != 2, "invalid input format");
+
+    edges = (int *) malloc(4 * edge_count * sizeof(int));
+    abort_if(!edges, "could not allocate edges\n");
+
+    capacities = (double *) malloc(2 * edge_count * sizeof(double));
+    abort_if(!capacities, "could not allocate capacities");
+
+    for (int i = 0; i < edge_count; i++)
+    {
+        int from, to, cap;
+
+        rval = fscanf(f, "%d %d %d ", &from, &to, &cap);
+        abort_if(rval != 3, "invalid input format");
+
+        edges[i*4] = edges[i*4+3] = from;
+        edges[i*4+1] = edges[i*4 + 2] = to;
+        capacities[2 * i] = cap;
+        capacities[2 * i + 1] = 0;
+    }
+
+    rval = graph_build(node_count, 2 * edge_count, edges, 1, &graph);
+    abort_if(rval, "graph_build failed");
+
+    for (int i = 0; i < edge_count; i++)
+    {
+        graph.edges[2*i].reverse = &graph.edges[2*i+1];
+        graph.edges[2*i+1].reverse = &graph.edges[2*i];
+    }
+
+    flow = (double *) malloc(graph.edge_count * sizeof(double));
+    abort_if(!flow, "could not allocate flow");
+
+    struct Node *from = &graph.nodes[0];
+    struct Node *to = &graph.nodes[graph.node_count - 1];
+
+    rval = flow_find_max_flow(&graph, capacities, from, to, flow, &flow_value);
+    abort_if(rval, "flow_find_max_flow failed");
+
+    log_info("Optimal flow has value %f\n", flow_value);
+    for (int i = 0; i < graph.edge_count; i++)
+    {
+        struct Edge *e = &graph.edges[i];
+        if(flow[e->index] <= 0) continue;
+
+        log_info("  %d %d %6.2f / %6.2f\n", e->from->index, e->to->index, flow[e->index], capacities[e->index]);
+    }
+
+    CLEANUP:
+    if (capacities) free(capacities);
+    if (edges) free(edges);
+    if (flow) free(flow);
+    return rval;
+}
+
 int main_tsp(int ac, char **av)
 {
     int rval = 0;
@@ -172,7 +246,8 @@ static int parse_arguments_tsp(int ac, char **av)
 
 int main(int ac, char **av)
 {
-    return main_gtsp(ac, av);
+    return test_max_flow();
+//    return main_gtsp(ac, av);
 //  return main_tsp(ac, av);
 }
 

src/tsp.c

@@ -38,7 +38,7 @@ int TSP_init_lp(struct LP *lp, struct TSPData *data)
         abort_if(rval, "LP_new_row failed");
     }
 
-    /* Build a column for each edge of the graph */
+    /* Build a column for each edge_index of the graph */
     double lb = 0.0;
     double ub = 1.0;
     int cmatbeg = 0;
@@ -83,7 +83,7 @@ int TSP_find_violated_subtour_elimination_cut(
     abort_if(rval, "LP_optimize failed");
     abort_if(is_infeasible, "LP is infeasible");
 
-    rval = graph_build(ncount, edge_count, edges, &G);
+    rval = graph_build(ncount, edge_count, edges, 0, &G);
     abort_if(rval, "graph_build failed");
 
     x = (double *) malloc(edge_count * sizeof(double));
@@ -185,7 +185,7 @@ int TSP_is_graph_connected(
 {
     for (int i = 0; i < G->node_count; i++)
     {
-        G->node_list[i].mark = 0;
+        G->nodes[i].mark = 0;
         island_nodes[i] = -1;
     }
 
@@ -193,7 +193,7 @@ int TSP_is_graph_connected(
 
     for (int i = 0; i < G->node_count; i++)
     {
-        if (G->node_list[i].mark != 0) continue;
+        if (G->nodes[i].mark != 0) continue;
 
         island_sizes[current_island] = 0;
 
@@ -224,29 +224,29 @@ int TSP_find_closest_neighbor_tour(
     struct Graph G;
     graph_init(&G);
 
-    rval = graph_build(node_count, edge_count, edges, &G);
+    rval = graph_build(node_count, edge_count, edges, 0, &G);
     abort_if(rval, "graph_build failed");
 
     for (int j = 0; j < node_count; j++)
-        G.node_list[j].mark = 0;
+        G.nodes[j].mark = 0;
 
     for (int j = 0; j < node_count; j++)
     {
         if (j == node_count - 1)
-            G.node_list[start].mark = 0;
+            G.nodes[start].mark = 0;
 
-        struct Node *pn = &G.node_list[current_node];
+        struct Node *pn = &G.nodes[current_node];
         pn->mark = 1;
 
         int closest_neighbor = -1;
         int closest_edge_length = 10000000;
 
-        for (int i = 0; i < pn->deg; i++)
+        for (int i = 0; i < pn->degree; i++)
         {
-            int edge = pn->adj[i].e;
+            int edge = pn->adj[i].edge_index;
-            int neighbor = pn->adj[i].n;
+            int neighbor = pn->adj[i].neighbor_index;
 
-            if (G.node_list[neighbor].mark == 1) continue;
+            if (G.nodes[neighbor].mark == 1) continue;
             if (elen[edge] > closest_edge_length) continue;
 
             closest_neighbor = neighbor;
@@ -439,7 +439,7 @@ double TSP_find_initial_solution(struct TSPData *data)
 {
     double best_val = 1e99;
 
-    log_verbose("Finding closest neighbor tour\n");
+    log_verbose("Finding closest neighbor_index tour\n");
     for (int i = 0; i < data->node_count; i++)
     {
         int path_length = 0;