bisect.

.github/workflows/jvm_tests.yml

@@ -93,19 +93,10 @@ jobs:
 
     - name: Test XGBoost4J (Core, Spark, Examples)
       run: |
-        rm -rfv build/
         cd jvm-packages
         mvn -B test
-      if: matrix.os == 'ubuntu-latest'  # Distributed training doesn't work on Windows
-      env:
-        RABIT_MOCK: ON
-
 
     - name: Build and Test XGBoost4J with scala 2.13
       run: |
-        rm -rfv build/
         cd jvm-packages
         mvn -B clean install test -Pdefault,scala-2.13
-      if: matrix.os == 'ubuntu-latest'  # Distributed training doesn't work on Windows
-      env:
-        RABIT_MOCK: ON

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014-2023 by Contributors
+ Copyright (c) 2014-2024 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/CommunicatorRobustnessSuite.scala

@@ -89,22 +89,18 @@ class CommunicatorRobustnessSuite extends AnyFunSuite with PerTest {
 
     val workerCount: Int = numWorkers
 
-    val dummyTasks = rdd.mapPartitions { iter =>
+    rdd.mapPartitions { iter =>
       val index = iter.next()
       Communicator.init(trackerEnvs)
+      val a = Array(1.0f, 2.0f, 3.0f)
+      System.out.println(a.mkString(", "))
+      val b = Communicator.allReduce(a, Communicator.OpType.SUM)
+      for (i <- 0 to 2) {
+        assert(a(i) * workerCount == b(i))
+      }
       Communicator.shutdown()
       Iterator(index)
-    }.cache()
-
-    val sparkThread = new Thread() {
-      override def run(): Unit = {
-        // forces a Spark job.
-        dummyTasks.foreachPartition(() => _)
-      }
-    }
-
-    sparkThread.setUncaughtExceptionHandler(tracker)
-    sparkThread.start()
+    }.collect()
   }
 
   test("should allow the dataframe containing communicator calls to be partially evaluated for" +