Use swap to save on memory allocs

src/tree.rs

@@ -9,6 +9,8 @@
 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 // License for the specific language governing permissions and limitations
 // under the License.
+//
+use std::mem;
 
 use std::cmp::Ordering;
 use std::collections::VecDeque;
@@ -209,7 +211,8 @@ pub fn balanced_cut_edge(
  // this will be false if root
  let neighbor = unseen_neighbors[0];
  pops[neighbor.index()] += pop.clone();
- let mut current_partition_tracker = same_partition_tracker[node.index()].clone();
+ let mut current_partition_tracker = Vec::<usize>::new();
+ mem::swap(&mut current_partition_tracker, &mut same_partition_tracker[node.index()]);
  same_partition_tracker[neighbor.index()].append(&mut current_partition_tracker);
  // eprintln!("node pushed to queue (pop = {}, target = {}): {}", pops[neighbor.index()], pop_target, neighbor.index());
 
@@ -270,7 +273,7 @@ pub fn bipartition_tree(
  let mut balanced_nodes: Vec<(usize, Vec<usize>)> = vec![];
 
  while balanced_nodes.len() == 0 {
- // Wee: https://pyo3.rs/v0.15.1/memory.html#gil-bound-memory
+ // See: https://pyo3.rs/v0.15.1/memory.html#gil-bound-memory
  // (workaround to force objects to be gc'ed on each loop)
  let pool = unsafe { py.new_pool() };
  let py = pool.python();