Implement spliterator for both nodes and edges (#240)

* Implement spliterator for both nodes and edges, while keeping fallback on iterator()

* Locking on toArray, toCollection and toSet for wrappers and parallel

* Optimise imports

* Set version to 0.8.0-SNAPSHOT

* Fix sizing issue with node's spliterator and create custom one for graph view

* Also fix edge spliterator, introducing both SIZED and non SIZED options

* Set default node block to 8192

* Improve unit tests for ede spliterator

Author: mbastian

pom.xml

@@ -3,7 +3,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>org.gephi</groupId>
     <artifactId>graphstore</artifactId>
-    <version>0.7.4-SNAPSHOT</version>
+    <version>0.8.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>GraphStore</name>

src/main/java/org/gephi/graph/api/EdgeIterable.java

@@ -20,6 +20,8 @@
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 /**
  * An edge iterable.
@@ -63,10 +65,24 @@ public interface EdgeIterable extends ElementIterable<Edge> {
     @Override
     public Set<Edge> toSet();
 
+    /**
+     * Returns a Spliterator over the edges.
+     * <p>
+     * Implementations return a splittable, sized, fail-fast spliterator suitable
+     * for parallel streams. When not possible, a non-splittable spliterator is
+     * returned.
+     *
+     * @return edge spliterator
+     */
+    @Override
+    default Spliterator<Edge> spliterator() {
+        return ElementIterable.super.spliterator();
+    }
+
     /**
      * Empty edge iterable.
      */
-    static final class EdgeIterableEmpty implements Iterator<Edge>, EdgeIterable {
+    final class EdgeIterableEmpty implements Iterator<Edge>, EdgeIterable {
 
         @Override
         public boolean hasNext() {
@@ -88,6 +104,11 @@ public Iterator<Edge> iterator() {
             return this;
         }
 
+        @Override
+        public Spliterator<Edge> spliterator() {
+            return Spliterators.emptySpliterator();
+        }
+
         @Override
         public Edge[] toArray() {
             return new Edge[0];

src/main/java/org/gephi/graph/api/ElementIterable.java

@@ -20,6 +20,10 @@
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 /**
  * Element iterable.
@@ -41,6 +45,25 @@ public interface ElementIterable<T extends Element> extends Iterable<T> {
     @Override
     public Iterator<T> iterator();
 
+    /**
+     * Creates a new sequential stream, based on the spliterator returned.
+     *
+     * @return stream
+     */
+    default Stream<T> stream() {
+        return StreamSupport.stream(spliterator(), false);
+    }
+
+    /**
+     * Creates a new sequential and parallel stream, based on the spliterator
+     * returned.
+     *
+     * @return stream
+     */
+    default Stream<T> parallelStream() {
+        return StreamSupport.stream(spliterator(), true);
+    }
+
     /**
      * Returns the iterator content as an array.
      *
@@ -92,6 +115,11 @@ public Iterator<Element> iterator() {
             return this;
         }
 
+        @Override
+        public Spliterator<Element> spliterator() {
+            return Spliterators.emptySpliterator();
+        }
+
         @Override
         public Element[] toArray() {
             return new Node[0];

src/main/java/org/gephi/graph/api/NodeIterable.java

@@ -20,6 +20,8 @@
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
 
 /**
  * A node iterable.
@@ -63,6 +65,20 @@ public interface NodeIterable extends ElementIterable<Node> {
     @Override
     public Set<Node> toSet();
 
+    /**
+     * Returns a Spliterator over the nodes.
+     * <p>
+     * Implementations return a splittable, sized, fail-fast spliterator suitable
+     * for parallel streams. When not possible, a non-splittable spliterator is
+     * returned.
+     *
+     * @return node spliterator
+     */
+    @Override
+    default Spliterator<Node> spliterator() {
+        return ElementIterable.super.spliterator();
+    }
+
     /**
      * Empty node iterable.
      */
@@ -88,6 +104,11 @@ public Iterator<Node> iterator() {
             return this;
         }
 
+        @Override
+        public Spliterator<Node> spliterator() {
+            return Spliterators.emptySpliterator();
+        }
+
         @Override
         public Node[] toArray() {
             return new Node[0];

src/main/java/org/gephi/graph/impl/ColumnObserverImpl.java

@@ -19,6 +19,7 @@
 import cern.colt.bitvector.QuickBitVector;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 import it.unimi.dsi.fastutil.objects.ObjectList;
+import it.unimi.dsi.fastutil.objects.ObjectLists;
 import org.gephi.graph.api.AttributeUtils;
 import org.gephi.graph.api.Column;
 import org.gephi.graph.api.ColumnDiff;
@@ -155,7 +156,8 @@ protected final class NodeColumnDiffImpl extends ColumnDiffImpl<Node> {
         @Override
         public NodeIterable getTouchedElements() {
             if (!touchedElements.isEmpty()) {
-                return graphStore.getNodeIterableWrapper(touchedElements.iterator(), false);
+                return new NodeIterableWrapper(() -> ObjectLists.unmodifiable(touchedElements).iterator(),
+                        () -> ObjectLists.unmodifiable(touchedElements).spliterator(), null);
 
             }
             return NodeIterable.NodeIterableEmpty.EMPTY;
@@ -167,8 +169,8 @@ protected final class EdgeColumnDiffImpl extends ColumnDiffImpl<Edge> {
         @Override
         public EdgeIterable getTouchedElements() {
             if (!touchedElements.isEmpty()) {
-                return graphStore.getEdgeIterableWrapper(touchedElements.iterator(), false);
-
+                return new EdgeIterableWrapper(() -> ObjectLists.unmodifiable(touchedElements).iterator(),
+                        () -> ObjectLists.unmodifiable(touchedElements).spliterator(), null);
             }
             return EdgeIterable.EdgeIterableEmpty.EMPTY;
         }

src/main/java/org/gephi/graph/impl/EdgeIterableWrapper.java

@@ -16,21 +16,32 @@
 package org.gephi.graph.impl;
 
 import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.function.Supplier;
+import java.util.stream.StreamSupport;
 import org.gephi.graph.api.Edge;
 import org.gephi.graph.api.EdgeIterable;
 
 public class EdgeIterableWrapper extends ElementIterableWrapper<Edge> implements EdgeIterable {
 
-    public EdgeIterableWrapper(Iterator<Edge> iterator) {
-        super(iterator);
+    public EdgeIterableWrapper(Supplier<Iterator<Edge>> iteratorSupplier, GraphLockImpl lock) {
+        super(iteratorSupplier, lock);
     }
 
-    public EdgeIterableWrapper(Iterator<Edge> iterator, GraphLockImpl lock) {
-        super(iterator, lock);
+    public EdgeIterableWrapper(Supplier<Iterator<Edge>> iteratorSupplier, Supplier<Spliterator<Edge>> spliteratorSupplier, GraphLockImpl lock) {
+        super(iteratorSupplier, spliteratorSupplier, lock);
     }
 
     @Override
     public Edge[] toArray() {
-        return toArray(new Edge[0]);
+        if (parallelPossible && lock != null) {
+            lock.readLock();
+            try {
+                return StreamSupport.stream(spliterator(), true).toArray(Edge[]::new);
+            } finally {
+                lock.readUnlock();
+            }
+        }
+        return StreamSupport.stream(spliterator(), parallelPossible).toArray(Edge[]::new);
     }
 }