Hi
Sorry for the late reply, I have been away for some time.
Yes, each thread requires some data per node. More specifically it requires around 48 bytes per node to store among other things: which node this is, the parent in the search graph, the cost to get to that node and some other stuff. Since multiple threads and thus path searches run in parallel this data cannot be shared. You have maybe 960*960*5 = 4608000 nodes (assuming the layered grid graph has at most 3 layers), so I would expect each thread to use something like 230 mb of ram.