bugfix: overflow of graphx Edge compare function

Author: Zhen Peng <zhenpeng01@baidu.com>

Closes #769 from zhpengg/bugfix-graphx-edge-compare and squashes the following commits:

8a978ff [Zhen Peng] add ut for graphx Edge.lexicographicOrdering.compare
413c258 [Zhen Peng] there maybe a overflow for two Long's substraction

1 files changed, 39 insertions, 0 deletions

diff --git a/graphx/src/test/scala/org/apache/spark/graphx/EdgeSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/EdgeSuite.scala
new file mode 100644
index 0000000000..5a2c73b414
--- /dev/null
+++ b/graphx/src/test/scala/org/apache/spark/graphx/EdgeSuite.scala
@@ -0,0 +1,39 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.graphx
+
+import org.scalatest.FunSuite
+
+class EdgeSuite extends FunSuite {
+  test ("compare") {
+    // decending order
+    val testEdges: Array[Edge[Int]] = Array(
+      Edge(0x7FEDCBA987654321L, -0x7FEDCBA987654321L, 1), 
+      Edge(0x2345L, 0x1234L, 1), 
+      Edge(0x1234L, 0x5678L, 1), 
+      Edge(0x1234L, 0x2345L, 1), 
+      Edge(-0x7FEDCBA987654321L, 0x7FEDCBA987654321L, 1)
+    )
+    // to ascending order
+    val sortedEdges = testEdges.sorted(Edge.lexicographicOrdering[Int])
+    
+    for (i <- 0 until testEdges.length) {
+      assert(sortedEdges(i) == testEdges(testEdges.length - i - 1))
+    }
+  }
+}