[jvm-packages]add feature size for LabelPoint and DataBatch (#5303)

* fix type error

* Validate number of features.

* resolve comments

* add feature size for LabelPoint and DataBatch

* pass the feature size to native

* move feature size validating tests into a separate suite

* resolve comments

Co-authored-by: fis <jm.yuan@outlook.com>

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/Booster.java

@@ -49,7 +49,6 @@ public class Booster implements Serializable, KryoSerializable {
    */
   Booster(Map<String, Object> params, DMatrix[] cacheMats) throws XGBoostError {
     init(cacheMats);
-    setParam("validate_features", "0");
     setParams(params);
   }
 

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/DataBatch.java

@@ -27,14 +27,17 @@ class DataBatch {
   final int[] featureIndex;
   /** value of each non-missing entry in the sparse matrix */
   final float[] featureValue ;
+  /** feature columns */
+  final int featureCols;
 
   DataBatch(long[] rowOffset, float[] weight, float[] label, int[] featureIndex,
-            float[] featureValue) {
+            float[] featureValue, int featureCols) {
     this.rowOffset = rowOffset;
     this.weight = weight;
     this.label = label;
     this.featureIndex = featureIndex;
     this.featureValue = featureValue;
+    this.featureCols = featureCols;
   }
 
   static class BatchIterator implements Iterator<DataBatch> {
@@ -56,9 +59,15 @@ class DataBatch {
       try {
         int numRows = 0;
         int numElem = 0;
+        int numCol  = -1;
         List<LabeledPoint> batch = new ArrayList<>(batchSize);
         while (base.hasNext() && batch.size() < batchSize) {
           LabeledPoint labeledPoint = base.next();
+          if (numCol == -1) {
+            numCol = labeledPoint.size();
+          } else if (numCol != labeledPoint.size()) {
+            throw new RuntimeException("Feature size is not the same");
+          }
           batch.add(labeledPoint);
           numElem += labeledPoint.values().length;
           numRows++;
@@ -91,7 +100,7 @@ class DataBatch {
         }
 
         rowOffset[batch.size()] = offset;
-        return new DataBatch(rowOffset, weight, label, featureIndex, featureValue);
+        return new DataBatch(rowOffset, weight, label, featureIndex, featureValue, numCol);
       } catch (RuntimeException runtimeError) {
         logger.error(runtimeError);
         return null;

jvm-packages/xgboost4j/src/main/scala/ml/dmlc/xgboost4j/LabeledPoint.scala

@@ -20,6 +20,7 @@ package ml.dmlc.xgboost4j
  * Labeled training data point.
  *
  * @param label Label of this point.
+ * @param size Feature dimensionality
  * @param indices Feature indices of this point or `null` if the data is dense.
  * @param values Feature values of this point.
  * @param weight Weight of this point.
@@ -28,6 +29,7 @@ package ml.dmlc.xgboost4j
  */
 case class LabeledPoint(
     label: Float,
+    size: Int,
     indices: Array[Int],
     values: Array[Float],
     weight: Float = 1f,
@@ -36,8 +38,11 @@ case class LabeledPoint(
   require(indices == null || indices.length == values.length,
     "indices and values must have the same number of elements")
 
-  def this(label: Float, indices: Array[Int], values: Array[Float]) = {
+  require(indices == null || size >= indices.length,
+    "feature dimensionality must be greater equal than size of indices")
+
+  def this(label: Float, size: Int, indices: Array[Int], values: Array[Float]) = {
     // [[weight]] default duplicated to disambiguate the constructor call.
-    this(label, indices, values, 1.0f)
+    this(label, size, indices, values, 1.0f)
   }
 }