predictor-spark work with model built from scala libs

[shaowei-su]

hi Komiya,
This is a very interesting project you've built!
I have one question: is it possible to load model built from "ml.dmlc.xgboost4j.scala.{XGBoost, DMatrix}" libraries with the predictor-spark package?

I was able to do this without error but the model looks strange to me:
scala> model.numFeatures
res15: Int = -1

and the prediction results are completely wrong.

Thanks.

[shaowei-su]

basically it can not load spark model info correctly:

scala> pred.getSparkModelParam
res28: biz.k11i.xgboost.spark.SparkModelParam = null

then the model can not be reconstructed

      xgboostPredictor.getSparkModelParam match {
        case param: SparkModelParam =>
          val model = param.getModelType match {
            case "_cls_" => loadClassificationModel(xgboostPredictor, param)
            case "_reg_" => loadRegressionModel(xgboostPredictor, param)
          }