Predict using dump model for ranking task


I run xgboost model with the objective of rank:ndcg on python.
I want to test manually the prediction by running on trees from dump model function.

my questions are:

  1. is the result of the model for ranking task is the sum of all each tree leaf?
  2. is dump model order the trees like the predict does? which mean if I set the ntree_limit to be 1 I can check only the first tree in the dump?
  3. is there a problem with the numeric representation using python and dumping it to json?


  1. Yes
  2. The order between items in each query group is determined by the relative size of the prediction for the items.