Merge pull request #944 from CodingCat/scala_examples

Scala examples

jvm-packages/xgboost4j-example/README.md

@@ -11,6 +11,17 @@ XGBoost4J Code Examples
 * [Predicting leaf indices](src/main/java/ml/dmlc/xgboost4j/java/example/PredictLeafIndices.java)
 * [External Memory](src/main/java/ml/dmlc/xgboost4j/java/example/ExternalMemory.java)
 
+## Scala API
+
+* [Basic walkthrough of wrappers](src/main/java/ml/dmlc/xgboost4j/scala/example/BasicWalkThrough.scala)
+* [Cutomize loss function, and evaluation metric](src/main/java/ml/dmlc/xgboost4j/scala/example/CustomObjective.scala)
+* [Boosting from existing prediction](src/main/java/ml/dmlc/xgboost4j/scala/example/BoostFromPrediction.scala)
+* [Predicting using first n trees](src/main/java/ml/dmlc/xgboost4j/scala/example/PredictFirstNtree.scala)
+* [Generalized Linear Model](src/main/java/ml/dmlc/xgboost4j/scala/example/GeneralizedLinearModel.scala)
+* [Cross validation](src/main/java/ml/dmlc/xgboost4j/java/example/CrossValidation.scala)
+* [Predicting leaf indices](src/main/java/ml/dmlc/xgboost4j/scala/example/PredictLeafIndices.scala)
+* [External Memory](src/main/java/ml/dmlc/xgboost4j/scala/example/ExternalMemory.scala)
+
 ## Spark API
 * [Distributed Training with Spark](src/main/scala/ml/dmlc/xgboost4j/scala/spark/example/DistTrainWithSpark.scala)
 

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/BasicWalkThrough.scala

@@ -0,0 +1,98 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import java.io.File
+import java.util
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.java.{DMatrix => JDMatrix}
+import ml.dmlc.xgboost4j.java.example.util.DataLoader
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class BasicWalkThrough {
+  def main(args: Array[String]): Unit = {
+    import BasicWalkThrough._
+    val trainMax = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMax = new DMatrix("../../demo/data/agaricus.txt.test")
+
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMax
+    watches += "test" -> testMax
+
+    val round = 2
+    // train a model
+    val booster = XGBoost.train(params.toMap, trainMax, round, watches.toMap)
+    // predict
+    val predicts = booster.predict(testMax)
+    // save model to model path
+    val file = new File("./model")
+    if (!file.exists()) {
+      file.mkdirs()
+    }
+    booster.saveModel(file.getAbsolutePath + "/xgb.model")
+    // dump model
+    booster.getModelDump(file.getAbsolutePath + "/dump.raw.txt", false)
+    // dump model with feature map
+    booster.getModelDump(file.getAbsolutePath + "/featmap.txt", false)
+    // save dmatrix into binary buffer
+    testMax.saveBinary(file.getAbsolutePath + "/dtest.buffer")
+
+    // reload model and data
+    val booster2 = XGBoost.loadModel(file.getAbsolutePath + "/xgb.model")
+    val testMax2 = new DMatrix(file.getAbsolutePath + "/dtest.buffer")
+    val predicts2 = booster2.predict(testMax2)
+
+    // check predicts
+    println(checkPredicts(predicts, predicts2))
+
+    // build dmatrix from CSR Sparse Matrix
+    println("start build dmatrix from csr sparse data ...")
+    val spData = DataLoader.loadSVMFile("../../demo/data/agaricus.txt.train")
+    val trainMax2 = new DMatrix(spData.rowHeaders, spData.colIndex, spData.data,
+      JDMatrix.SparseType.CSR)
+    trainMax2.setLabel(spData.labels)
+
+    // specify watchList
+    val watches2 = new mutable.HashMap[String, DMatrix]
+    watches2 += "train" -> trainMax2
+    watches2 += "test" -> testMax2
+    val booster3 = XGBoost.train(params.toMap, trainMax2, round, watches2.toMap, null, null)
+    val predicts3 = booster3.predict(testMax2)
+    println(checkPredicts(predicts, predicts3))
+  }
+}
+
+object BasicWalkThrough {
+  def checkPredicts(fPredicts: Array[Array[Float]], sPredicts: Array[Array[Float]]): Boolean = {
+    require(fPredicts.length == sPredicts.length, "the comparing predicts must be with the same " +
+      "length")
+    for (i <- fPredicts.indices) {
+      if (!java.util.Arrays.equals(fPredicts(i), sPredicts(i))) {
+        return false
+      }
+    }
+    true
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/BoostFromPrediction.scala

@@ -0,0 +1,53 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class BoostFromPrediction {
+  def main(args: Array[String]): Unit = {
+    println("start running example to start from a initial prediction")
+
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test")
+
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 2
+    // train a model
+    val booster = XGBoost.train(params.toMap, trainMat, round, watches.toMap)
+
+    val trainPred = booster.predict(trainMat, true)
+    val testPred = booster.predict(testMat, true)
+
+    trainMat.setBaseMargin(trainPred)
+    testMat.setBaseMargin(testPred)
+
+    System.out.println("result of running from initial prediction")
+    val booster2 = XGBoost.train(params.toMap, trainMat, 1, watches.toMap, null, null)
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/CrossValidation.scala

@@ -0,0 +1,46 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class CrossValidation {
+  def main(args: Array[String]): Unit = {
+    val trainMat: DMatrix = new DMatrix("../../demo/data/agaricus.txt.train")
+
+    // set params
+    val params = new mutable.HashMap[String, Any]
+
+    params.put("eta", 1.0)
+    params.put("max_depth", 3)
+    params.put("silent", 1)
+    params.put("nthread", 6)
+    params.put("objective", "binary:logistic")
+    params.put("gamma", 1.0)
+    params.put("eval_metric", "error")
+
+    // do 5-fold cross validation
+    val round: Int = 2
+    val nfold: Int = 5
+    // set additional eval_metrics
+    val metrics: Array[String] = null
+
+    val evalHist: Array[String] =
+      XGBoost.crossValidation(params.toMap, trainMat, round, nfold, metrics, null, null)
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/CustomObjective.scala

@@ -0,0 +1,157 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+import scala.collection.mutable.ListBuffer
+
+import ml.dmlc.xgboost4j.java.XGBoostError
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix, EvalTrait, ObjectiveTrait}
+import org.apache.commons.logging.{LogFactory, Log}
+
+/**
+ * an example user define objective and eval
+ * NOTE: when you do customized loss function, the default prediction value is margin
+ * this may make buildin evalution metric not function properly
+ * for example, we are doing logistic loss, the prediction is score before logistic transformation
+ * he buildin evaluation error assumes input is after logistic transformation
+ * Take this in mind when you use the customization, and maybe you need write customized evaluation
+ * function
+ *
+ */
+class CustomObjective {
+
+  /**
+   * loglikelihoode loss obj function
+   */
+  class LogRegObj extends ObjectiveTrait {
+    private val logger: Log = LogFactory.getLog(classOf[LogRegObj])
+    /**
+     * user define objective function, return gradient and second order gradient
+     *
+     * @param predicts untransformed margin predicts
+     * @param dtrain   training data
+     * @return List with two float array, correspond to first order grad and second order grad
+     */
+    override def getGradient(predicts: Array[Array[Float]], dtrain: DMatrix)
+        : List[Array[Float]] = {
+      val nrow = predicts.length
+      val gradients = new ListBuffer[Array[Float]]
+      var labels: Array[Float] = null
+      try {
+        labels = dtrain.getLabel
+      } catch {
+        case e: XGBoostError =>
+          logger.error(e)
+          null
+        case _ =>
+          null
+      }
+      val grad = new Array[Float](nrow)
+      val hess = new Array[Float](nrow)
+      val transPredicts = transform(predicts)
+
+      for (i <- 0 until nrow) {
+        val predict = transPredicts(i)(0)
+        grad(i) = predict - labels(i)
+        hess(i) = predict * (1 - predict)
+      }
+      gradients += grad
+      gradients += hess
+      gradients.toList
+    }
+
+    /**
+     * simple sigmoid func
+     *
+     * @param input
+     * @return Note: this func is not concern about numerical stability, only used as example
+     */
+    def sigmoid(input: Float): Float = {
+      (1 / (1 + Math.exp(-input))).toFloat
+    }
+
+    def transform(predicts: Array[Array[Float]]): Array[Array[Float]] = {
+      val nrow = predicts.length
+      val transPredicts = Array.fill[Float](nrow, 1)(0)
+      for (i <- 0 until nrow) {
+        transPredicts(i)(0) = sigmoid(predicts(i)(0))
+      }
+      transPredicts
+    }
+
+  }
+
+  class EvalError extends EvalTrait {
+
+    val logger = LogFactory.getLog(classOf[EvalError])
+
+    private[xgboost4j] var evalMetric: String = "custom_error"
+
+    /**
+     * get evaluate metric
+     *
+     * @return evalMetric
+     */
+    override def getMetric: String = evalMetric
+
+    /**
+     * evaluate with predicts and data
+     *
+     * @param predicts predictions as array
+     * @param dmat     data matrix to evaluate
+     * @return result of the metric
+     */
+    override def eval(predicts: Array[Array[Float]], dmat: DMatrix): Float = {
+      var error: Float = 0f
+      var labels: Array[Float] = null
+      try {
+        labels = dmat.getLabel
+      } catch {
+        case ex: XGBoostError =>
+          logger.error(ex)
+          return -1f
+      }
+      val nrow: Int = predicts.length
+      for (i <- 0 until nrow) {
+        if (labels(i) == 0.0 && predicts(i)(0) > 0) {
+          error += 1
+        } else if (labels(i) == 1.0 && predicts(i)(0) <= 0) {
+          error += 1
+        }
+      }
+      error / labels.length
+    }
+  }
+
+  def main(args: Array[String]): Unit = {
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test")
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 2
+    // train a model
+    val booster = XGBoost.train(params.toMap, trainMat, round, watches.toMap)
+    XGBoost.train(params.toMap, trainMat, round, watches.toMap, new LogRegObj, new EvalError)
+  }
+
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/ExternalMemory.scala

@@ -0,0 +1,59 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class ExternalMemory {
+  def main(args: Array[String]): Unit = {
+    // this is the only difference, add a # followed by a cache prefix name
+    // several cache file with the prefix will be generated
+    // currently only support convert from libsvm file
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train#dtrain.cache")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test#dtest.cache")
+
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    // performance notice: set nthread to be the number of your real cpu
+    // some cpu offer two threads per core, for example, a 4 core cpu with 8 threads, in such case
+    // set nthread=4
+    // param.put("nthread", num_real_cpu);
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 2
+    // train a model
+    val booster = XGBoost.train(params.toMap, trainMat, round, watches.toMap)
+
+    val trainPred = booster.predict(trainMat, true)
+    val testPred = booster.predict(testMat, true)
+
+    trainMat.setBaseMargin(trainPred)
+    testMat.setBaseMargin(testPred)
+
+    System.out.println("result of running from initial prediction")
+    val booster2 = XGBoost.train(params.toMap, trainMat, 1, watches.toMap, null, null)
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/GeneralizedLinearModel.scala

@@ -0,0 +1,60 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+import ml.dmlc.xgboost4j.scala.example.util.CustomEval
+
+
+/**
+ * this is an example of fit generalized linear model in xgboost
+ * basically, we are using linear model, instead of tree for our boosters
+ */
+class GeneralizedLinearModel {
+  def main(args: Array[String]): Unit = {
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test")
+
+    // specify parameters
+    // change booster to gblinear, so that we are fitting a linear model
+    // alpha is the L1 regularizer
+    // lambda is the L2 regularizer
+    // you can also set lambda_bias which is L2 regularizer on the bias term
+    val params = new mutable.HashMap[String, Any]()
+    params += "alpha" -> 0.0001
+    params += "boosterh" -> "gblinear"
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    // normally, you do not need to set eta (step_size)
+    // XGBoost uses a parallel coordinate descent algorithm (shotgun),
+    // there could be affection on convergence with parallelization on certain cases
+    // setting eta to be smaller value, e.g 0.5 can make the optimization more stable
+    // param.put("eta", "0.5");
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 4
+    val booster = XGBoost.train(params.toMap, trainMat, 1, watches.toMap, null, null)
+    val predicts = booster.predict(testMat)
+    val eval = new CustomEval
+    println(s"error=${eval.eval(predicts, testMat)}")
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/PredictFirstNTree.scala

@@ -0,0 +1,53 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.example.util.CustomEval
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class PredictFirstNTree {
+
+  def main(args: Array[String]): Unit = {
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test")
+
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 3
+    // train a model
+    val booster = XGBoost.train(params.toMap, trainMat, round, watches.toMap)
+
+    // predict use 1 tree
+    val predicts1 = booster.predict(testMat, false, 1)
+    // by default all trees are used to do predict
+    val predicts2 = booster.predict(testMat)
+
+    val eval = new CustomEval
+    println("error of predicts1: " + eval.eval(predicts1, testMat))
+    println("error of predicts2: " + eval.eval(predicts2, testMat))
+  }
+
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/PredictLeafIndices.scala

@@ -0,0 +1,56 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example
+
+import java.util
+
+import scala.collection.mutable
+
+import ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}
+
+class PredictLeafIndices {
+
+  def main(args: Array[String]): Unit = {
+    val trainMat = new DMatrix("../../demo/data/agaricus.txt.train")
+    val testMat = new DMatrix("../../demo/data/agaricus.txt.test")
+
+    val params = new mutable.HashMap[String, Any]()
+    params += "eta" -> 1.0
+    params += "max_depth" -> 2
+    params += "silent" -> 1
+    params += "objective" -> "binary:logistic"
+
+    val watches = new mutable.HashMap[String, DMatrix]
+    watches += "train" -> trainMat
+    watches += "test" -> testMat
+
+    val round = 3
+    val booster = XGBoost.train(params.toMap, trainMat, round, watches.toMap)
+
+    // predict using first 2 tree
+    val leafIndex = booster.predictLeaf(testMat, 2)
+    for (leafs <- leafIndex) {
+      println(java.util.Arrays.toString(leafs))
+    }
+
+    // predict all trees
+    val leafIndex2 = booster.predictLeaf(testMat, 0)
+    for (leafs <- leafIndex) {
+      println(java.util.Arrays.toString(leafs))
+    }
+  }
+}

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/flink/DistTrainWithFlink.scala

@@ -13,11 +13,10 @@
  See the License for the specific language governing permissions and
  limitations under the License.
  */
-package ml.dmlc.xgboost4j.scala.flink.example
+package ml.dmlc.xgboost4j.scala.example.flink
 
 import ml.dmlc.xgboost4j.scala.flink.XGBoost
-import org.apache.flink.api.scala._
-import org.apache.flink.api.scala.ExecutionEnvironment
+import org.apache.flink.api.scala.{ExecutionEnvironment, _}
 import org.apache.flink.ml.MLUtils
 
 object DistTrainWithFlink {

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

@@ -14,11 +14,11 @@
  limitations under the License.
  */
 
-package ml.dmlc.xgboost4j.scala.spark.example
+package ml.dmlc.xgboost4j.scala.example.spark
 
+import ml.dmlc.xgboost4j.scala.spark.XGBoost
 import org.apache.spark.SparkContext
 import org.apache.spark.mllib.util.MLUtils
-import ml.dmlc.xgboost4j.scala.spark.XGBoost
 
 object DistTrainWithSpark {
   def main(args: Array[String]): Unit = {

jvm-packages/xgboost4j-example/src/main/scala/ml/dmlc/xgboost4j/scala/example/util/CustomEval.scala

@@ -0,0 +1,60 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.example.util
+
+import ml.dmlc.xgboost4j.java.XGBoostError
+import ml.dmlc.xgboost4j.scala.{DMatrix, EvalTrait}
+import org.apache.commons.logging.{Log, LogFactory}
+
+class CustomEval extends EvalTrait {
+  private val logger: Log = LogFactory.getLog(classOf[CustomEval])
+  /**
+   * get evaluate metric
+   *
+   * @return evalMetric
+   */
+  override def getMetric: String = {
+    "custom_error"
+  }
+
+  /**
+   * evaluate with predicts and data
+   *
+   * @param predicts predictions as array
+   * @param dmat     data matrix to evaluate
+   * @return result of the metric
+   */
+  override def eval(predicts: Array[Array[Float]], dmat: DMatrix): Float = {
+    var error: Float = 0f
+    var labels: Array[Float] = null
+    try {
+      labels = dmat.getLabel
+    } catch {
+      case ex: XGBoostError =>
+        logger.error(ex)
+        return -1f
+    }
+    val nrow: Int = predicts.length
+    for (i <- 0 until nrow) {
+      if (labels(i) == 0.0 && predicts(i)(0) > 0.5) {
+        error += 1
+      } else if (labels(i) == 1.0 && predicts(i)(0) <= 0.5) {
+        error += 1
+      }
+    }
+    error / labels.length
+  }
+}

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

@@ -107,7 +107,6 @@ object XGBoost extends Serializable {
   def loadModelFromHadoop(modelPath: String)(implicit sparkContext: SparkContext): XGBoostModel = {
     val dataInStream = FileSystem.get(sparkContext.hadoopConfiguration).open(new Path(modelPath))
     val xgBoostModel = new XGBoostModel(SXGBoost.loadModel(dataInStream))
-    dataInStream.close()
     xgBoostModel
   }
 }

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

@@ -26,12 +26,11 @@ import ml.dmlc.xgboost4j.scala.{DMatrix, Booster}
 class XGBoostModel(booster: Booster)(implicit val sc: SparkContext) extends Serializable {
 
   /**
-    * Predict result with the given testset (represented as RDD)
-    */
+   * Predict result with the given testset (represented as RDD)
+   */
   def predict(testSet: RDD[Vector]): RDD[Array[Array[Float]]] = {
     import DataUtils._
     val broadcastBooster = testSet.sparkContext.broadcast(booster)
-    val dataUtils = testSet.sparkContext.broadcast(DataUtils)
     testSet.mapPartitions { testSamples =>
       val dMatrix = new DMatrix(new JDMatrix(testSamples, null))
       Iterator(broadcastBooster.value.predict(dMatrix))
@@ -46,10 +45,10 @@ class XGBoostModel(booster: Booster)(implicit val sc: SparkContext) extends Seri
   }
 
   /**
-    * Save the model as to HDFS-compatible file system.
- *
-    * @param modelPath The model path as in Hadoop path.
-    */
+   * Save the model as to HDFS-compatible file system.
+   *
+   * @param modelPath The model path as in Hadoop path.
+   */
   def saveModelToHadoop(modelPath: String): Unit = {
     val outputStream = FileSystem.get(sc.hadoopConfiguration).create(new Path(modelPath))
     booster.saveModel(outputStream)