From 372faf63eb51f6bdddf2a99d7b07364e29231fa6 Mon Sep 17 00:00:00 2001
From: zhangyi51 <zhangyi51@baidu.com>
Date: Thu, 12 Aug 2021 11:49:46 +0800
Subject: [PATCH] improve shortest path by traversing from less direction

Change-Id: I630dfa362882e4721a33a0dc42c3e32ea7477022
---
 .../algorithm/ShortestPathTraverser.java         | 16 +++++++---------
 .../records/DoubleWayMultiPathsRecords.java      |  5 +++++
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/ShortestPathTraverser.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/ShortestPathTraverser.java
index 151928964b..a2a5b1319e 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/ShortestPathTraverser.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/ShortestPathTraverser.java
@@ -120,16 +120,10 @@ public PathSet allShortestPaths(Id sourceV, Id targetV, Directions dir,
         Traverser traverser = new Traverser(sourceV, targetV, dir, labelMap,
                                             degree, skipDegree, capacity);
         while (true) {
+            paths = traverser.forward() ?
+                    traverser.forward(true) : traverser.backward(true);
             // Found, reach max depth or reach capacity, stop searching
-            if (!(paths = traverser.forward(true)).isEmpty() ||
-                --depth <= 0) {
-                break;
-            }
-            checkCapacity(traverser.capacity, traverser.accessed(),
-                          "shortest path");
-
-            if (!(paths = traverser.backward(true)).isEmpty() ||
-                --depth <= 0) {
+            if (!paths.isEmpty() || --depth <= 0) {
                 break;
             }
             checkCapacity(traverser.capacity, traverser.accessed(),
@@ -238,6 +232,10 @@ public PathSet backward(boolean all) {
             return results;
         }
 
+        public boolean forward() {
+            return this.record.lessSources();
+        }
+
         private boolean superNode(Id vertex, Directions direction) {
             if (this.skipDegree <= 0L) {
                 return false;
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
index ad76673e33..4ba60eede5 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/traversal/algorithm/records/DoubleWayMultiPathsRecords.java
@@ -112,6 +112,11 @@ public PathSet findPath(Id target, Function<Id, Boolean> filter,
         return results;
     }
 
+    public boolean lessSources() {
+        return this.sourceRecords.peek().size() <=
+               this.targetRecords.peek().size();
+    }
+
     @Override
     public long accessed() {
         return this.accessed;