Because it doubles in every node and OP has 300k of them[1]. It's not a leak, since memory is...well...accounted for and easily freed by either dropping Vec or

Because it doubles in every node and OP has 300k of them[1]. It's not a leak, since memory is...well...accounted for and easily freed by either dropping Vec or calling shirk_to_fit. IMO it's expected behavior. Honestly, if I had 300k Vecs, I would call `shrink_to_fit` even without that optimization. 1: Since the edge list calculation logic is run for one node at a time in sequence, the fact that it temporarily uses 132kb of memory would normally not be a problem at all. However, the new collect() optimization meant that that internal storage was being preserved in the final vec which got inserted into the list of edge lists, thus keeping around that 132kb of obsolete memory forever. Multiply that by 300k nodes and suddenly you’ve leaked the computer’s entire RAM.