[graph-tool] Memory usage

I was trying to do a nested degree-corrected SBM on my laptop, but I was running out of RAM, 14-15GB before stopping with "Killed". The graph is directed with 20k nodes 2.8m edges. Is that a typical amount of memory usage or did I do something wrong? If it's normal, is there any way for me to work around this such that I can run it on my computer