Latest commit 5d74578
Jan 22, 2017
As discussed in issue #1978, tree_method=hist ignores the parameter param.num_roots; it simply assumes that the tree has only one root. In particular, when InitData() method initializes row_set_collection_, it simply assigns all rows to node 0, the value that's hard-coded. For now, the updater will simply fail when num_roots exceeds 1. I will revise the updater soon to support multiple roots.