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Some comments for row partitioner. (#4832)

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This commit is contained in:
Jiaming Yuan
2019-09-06 03:01:42 -04:00
committed by GitHub
parent a5f232feb8
commit f90e7f9aa8
3 changed files with 45 additions and 13 deletions
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11
src/tree/updater_gpu_hist.cu
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@@ -152,8 +152,8 @@ struct ELLPackMatrix {
XGBOOST_DEVICE size_t BinCount() const { return gidx_fvalue_map.size(); }
// Get a matrix element, uses binary search for look up
// Return NaN if missing
// Get a matrix element, uses binary search for look up Return NaN if missing
// Given a row index and a feature index, returns the corresponding cut value
__device__ bst_float GetElement(size_t ridx, size_t fidx) const {
auto row_begin = row_stride * ridx;
auto row_end = row_begin + row_stride;
@@ -832,14 +832,15 @@ struct DeviceShard {
row_partitioner->UpdatePosition(
nidx, split_node.LeftChild(), split_node.RightChild(),
[=] __device__(bst_uint ridx) {
bst_float element =
// given a row index, returns the node id it belongs to
bst_float cut_value =
d_matrix.GetElement(ridx, split_node.SplitIndex());
// Missing value
int new_position = 0;
if (isnan(element)) {
if (isnan(cut_value)) {
new_position = split_node.DefaultChild();
} else {
if (element <= split_node.SplitCond()) {
if (cut_value <= split_node.SplitCond()) {
new_position = split_node.LeftChild();
} else {
new_position = split_node.RightChild();