/**
* CPU build implementation
*
* @param level
*/
public void buildCPU(int level) {
int prev_level = level - 1;
long start_node = 0;
long end_node = 0;
if (level > 1) {
start_node = max_level_id(level - 2) + 1;
end_node = max_level_id(level - 1);
}
m_instance_data.begin(Buffer.READ_WRITE);
// find min_max
for (int i = 0; i < m_instance_data.rows(); ++i) {
int node_id = m_leaf_node_ids[i];
if (!(node_id >= start_node && node_id <= end_node))
throw new RuntimeException("All instances should be in the leaves");
for (int att = 0; att < m_num_attributes; ++att) {
int node_offset = node_id * m_num_attributes + att;
Buffer attributes = m_instance_data.attributes();
double value = attributes.read((att + i * m_num_attributes) * DirectMemory.DOUBLE_SIZE);
double min = m_min_temp[node_offset];
double max = m_max_temp[node_offset];
if (value > max) m_max_temp[node_offset] = value;
if (value < min) m_min_temp[node_offset] = value;
}
}
// split by mean of widest dim
int split_candidate = -1;
double max_range = -1;
for (int node = (int) start_node; node <= end_node; ++node) {
// 1 thread
for (int att = 0; att < m_num_attributes; ++att) {
double min_val = m_min_temp[(node * m_num_attributes + att)];
double max_val = m_max_temp[(node * m_num_attributes + att)];
double abs_min_val = m_min_temp[att];
double abs_max_val = m_max_temp[att];
double range = (abs_max_val - abs_min_val);
if (range > 0) {
double node_range = (max_val - min_val) / range;
if (node_range > max_range) {
split_candidate = att;
max_range = node_range;
}
}
}
m_node_split_dim[node] = split_candidate;
m_node_split_value[node] =
m_min_temp[(node * m_num_attributes + split_candidate)] + max_range / 2;
}
for (int i = 0; i < m_instance_data.rows(); ++i) {
int node_id = m_leaf_node_ids[i];
int split_dim = m_node_split_dim[node_id];
double split_value = m_node_split_value[node_id];
double att_value =
m_instance_data
.attributes()
.read((split_dim + i * m_num_attributes) * DirectMemory.DOUBLE_SIZE);
if (att_value > split_value) m_leaf_node_ids[i] = (int) child(node_id) + 1;
else m_leaf_node_ids[i] = (int) child(node_id);
}
m_instance_data.commit();
}
public void sort(Buffer input, Buffer indices) {
nativeSort(input, m_temp, indices, m_dst, (int) (indices.byteSize() / DirectMemory.INT_SIZE));
}