Tentative balanced implementation

jgrapht · Feb 20, 2021 · eddd21d · eddd21d
1 parent de93f41
commit eddd21d
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Showing 2 changed files with 24 additions and 7 deletions.
diff --git a/jgrapht-unimi-dsi/src/main/java/org/jgrapht/sux4j/AbstractSuccinctUndirectedGraph.java b/jgrapht-unimi-dsi/src/main/java/org/jgrapht/sux4j/AbstractSuccinctUndirectedGraph.java
@@ -44,6 +44,8 @@ public abstract class AbstractSuccinctUndirectedGraph<E>
     extends
     AbstractSuccinctGraph<E>
 {
+    /** 2<sup>32</sup> &middot; &phi;, &phi; = (&#x221A;5 &minus; 1)/2. */
+    protected static final int INT_PHI = 0x9E3779B9;
 
     public AbstractSuccinctUndirectedGraph(final int n, final int m)
     {
@@ -100,13 +102,14 @@ public boolean hasNext()
                 int d = 0;
                 for (final E e : succ.apply(x)) {
                     final int y = Graphs.getOppositeVertex(graph, e, x);
+
                     if (sorted) {
-                        if (x <= y) {
+                        if (x * INT_PHI <= y * INT_PHI) {
                             s = IntArrays.grow(s, d + 1);
                             s[d++] = y;
                         }
                     } else {
-                        if (x >= y) {
+                        if (x * INT_PHI >= y * INT_PHI) {
                             s = IntArrays.grow(s, d + 1);
                             s[d++] = y;
                         }
@@ -178,11 +181,11 @@ public long nextLong()
             int d = 0;
             if (sorted) {
                 for (final E e : succ.apply(x))
-                    if (x <= Graphs.getOppositeVertex(graph, e, x))
+                    if (x * INT_PHI <= Graphs.getOppositeVertex(graph, e, x) * INT_PHI)
                         d++;
             } else {
                 for (final E e : succ.apply(x))
-                    if (x >= Graphs.getOppositeVertex(graph, e, x))
+                    if (x * INT_PHI >= Graphs.getOppositeVertex(graph, e, x) * INT_PHI)
                         d++;
             }
             x++;
@@ -205,7 +208,7 @@ public int outDegreeOf(final Integer vertex)
     protected boolean containsEdge(
         final EliasFanoIndexedMonotoneLongBigList successors, int x, int y)
     {
-        if (x > y) {
+        if (x * INT_PHI > y * INT_PHI) {
             final int t = x;
             x = y;
             y = t;

diff --git a/jgrapht-unimi-dsi/src/main/java/org/jgrapht/sux4j/SuccinctUndirectedGraph.java b/jgrapht-unimi-dsi/src/main/java/org/jgrapht/sux4j/SuccinctUndirectedGraph.java
@@ -144,6 +144,13 @@ public SuccinctUndirectedGraph(
     @Override
     public boolean containsEdge(final IntIntSortedPair e)
     {
+        int x = e.firstInt();
+        int y = e.secondInt();
+        if (x * INT_PHI > y * INT_PHI) {
+            final int t = x;
+            x = y;
+            y = t;
+        }
         return successors.indexOfUnsafe(((long) e.firstInt() << sourceShift) + e.secondInt()) != -1;
     }
 
@@ -216,7 +223,14 @@ public int getIndexFromEdge(final IntIntSortedPair e)
         final int target = e.secondInt();
         if (source < 0 || source >= n || target < 0 || target >= n)
             throw new IllegalArgumentException();
-        return (int) successors.indexOfUnsafe(((long) source << sourceShift) + target);
+        int x = source;
+        int y = target;
+        if (x * INT_PHI > y * INT_PHI) {
+            final int t = x;
+            x = y;
+            y = t;
+        }
+        return (int) successors.indexOfUnsafe(((long) x << sourceShift) + y);
     }
 
     /**
@@ -239,7 +253,7 @@ public IntIntSortedPair getEdge(final Integer sourceVertex, final Integer target
     {
         int x = sourceVertex;
         int y = targetVertex;
-        if (x > y) {
+        if (x * INT_PHI > y * INT_PHI) {
             final int t = x;
             x = y;
             y = t;