I’m running xgboost with objective `rank:ndcg`

and I have 3 questions:

- is the model knows how to use the position of the data? i need to send to the model the data sorted by qid and by position (ascending)?
- I know that the model is using num_pairsample - what is the value of this variable and can we change it? also it this variable mean the number of pairs the model is checking for the loss?