When I try to use the example json file in the javadoc of MultipleAdditiveTreesModel.java I receive the following error:
org.apache.solr.ltr.model.ModelException: Model type does not exist org.apache.solr.ltr.model.MultipleAdditiveTreesModel
The sample model from the documentation is working. The difference seems to be the quoted numbers. I can confirm that once quoted I no longer have the problem and the setter methods all expect Strings.
It's a little bit confusing as this error message does not really pin down the root of the problem.