From: Jonathan Zheng <jonathanzheng@hotmail.co.uk>
Date: Thu, 16 Jan 2020 00:19:18 +0000 (+0000)
Subject: made dijkstra clearer
X-Git-Tag: stable_release_2.44.0~12^2~15
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=269faa348076a1c85507f2b115ee3eda6be3ce67;p=graphviz

made dijkstra clearer
---

diff --git a/lib/neatogen/sgd.c b/lib/neatogen/sgd.c
index 9b794c255..ed63756bc 100644
--- a/lib/neatogen/sgd.c
+++ b/lib/neatogen/sgd.c
@@ -22,7 +22,8 @@ float calculate_stress(term *terms, int n_terms) {
 void fisheryates_shuffle(term *terms, int n_terms) {
     int i;
     for (i=n_terms-1; i>=1; i--) {
-        int j = (int)(drand48() * (i+1)); // TODO: better rng?
+        // srand48() is called in neatoinit.c, so no need to seed here
+        int j = (int)(drand48() * (i+1));
 
         term temp = terms[i];
         terms[i] = terms[j];
@@ -31,7 +32,8 @@ void fisheryates_shuffle(term *terms, int n_terms) {
 }
 // single source shortest paths that also builds terms as it goes
 // mostly copied from from stuff.c
-void dijkstra_single_source(graph_t *G, node_t *source, term *terms, int *offset) {
+// returns the number of terms built
+int dijkstra_single_source(graph_t *G, node_t *source, term *terms) {
     int t;
     node_t *v, *u;
     for (t = 0; (v = GD_neato_nlist(G)[t]); t++) {
@@ -40,19 +42,19 @@ void dijkstra_single_source(graph_t *G, node_t *source, term *terms, int *offset
     }
 
     ND_dist(source) = 0;
-    ND_hops(source) = 0;
     neato_enqueue(G, source);
 
     edge_t *e;
+    int offset = 0;
     while ((v = neato_dequeue(G))) {
         // if the target is fixed then always create a term as shortest paths are not calculated from there
         // if not fixed then only create a term if the target index is lower
         if (isFixed(v) || ND_id(v)<ND_id(source)) {
-            terms[*offset].i = source;
-            terms[*offset].j = v;
-            terms[*offset].d = ND_dist(v);
-            terms[*offset].w = 1 / (terms[*offset].d*terms[*offset].d);
-            (*offset)++;
+            terms[offset].i = source;
+            terms[offset].j = v;
+            terms[offset].d = ND_dist(v);
+            terms[offset].w = 1 / (terms[offset].d*terms[offset].d);
+            offset++;
         }
         for (e = agfstedge(G, v); e; e = agnxtedge(G, e, v)) {
             if ((u = agtail(e)) == v)
@@ -64,12 +66,12 @@ void dijkstra_single_source(graph_t *G, node_t *source, term *terms, int *offset
                 if (ND_heapindex(u) >= 0) {
                     heapup(G, u);
                 } else {
-                    ND_hops(u) = ND_hops(v) + 1;
                     neato_enqueue(G, u);
                 }
             }
         }
     }
+    return offset;
 }
 
 void sgd(graph_t *G, /* input graph */
@@ -96,7 +98,7 @@ void sgd(graph_t *G, /* input graph */
 
     // calculate term values through shortest paths
     int offset = 0;
-    GD_heap(G) = N_NEW(n + 1, node_t *);
+    GD_heap(G) = N_NEW(n, node_t *);
     GD_heapsize(G) = 0;
     if (Verbose) {
         fprintf(stderr, "calculating shortest paths:");
@@ -104,8 +106,9 @@ void sgd(graph_t *G, /* input graph */
     }
     for (i=0; i<n; i++) {
         node_t *source = GD_neato_nlist(G)[i];
-        if (!isFixed(source))
-            dijkstra_single_source(G, source, terms, &offset);
+        if (!isFixed(source)) {
+            offset += dijkstra_single_source(G, source, terms+offset);
+        }
     }
     free(GD_heap(G));
     assert(offset == n_terms);
@@ -132,11 +135,11 @@ void sgd(graph_t *G, /* input graph */
     initial_positions(G, n);
 
     // perform optimisation
-    int t;
     if (Verbose) {
         fprintf(stderr, "solving model:");
         start_timer();
     }
+    int t;
     for (t=0; t<MaxIter; t++) {
         fisheryates_shuffle(terms, n_terms);
         float eta = eta_max * exp(-lambda * t);
diff --git a/lib/neatogen/stuff.c b/lib/neatogen/stuff.c
index 87522bbd1..df38a13bd 100644
--- a/lib/neatogen/stuff.c
+++ b/lib/neatogen/stuff.c
@@ -264,7 +264,7 @@ int scan_graph_mode(graph_t * G, int mode)
     } else if (mode == MODE_SGD) {
 	Epsilon = .01;
 	getdouble(G, "epsilon", &Epsilon);
-	GD_neato_nlist(G) = N_NEW(nV + 1, node_t *);
+	GD_neato_nlist(G) = N_NEW(nV, node_t *);
 	for (i = 0, np = agfstnode(G); np; np = agnxtnode(G, np)) {
 	    GD_neato_nlist(G)[i] = np;
 	    ND_id(np) = i++;