Hi Gang,
This is the error message I see on the standard output:
Error: Exceeded density grid with x_grid = 490 and y_grid=2147483638.
Program stopped.
This is coming from the original DrL implementation that is embedded
inside igraph. This should not stop the program, though, so there is
definitely a bug on our side (the DrL implementation should have been
modified so it uses igraph's error reporting mechanism).
Anyway, your code seems to work if I replace IGRAPH_LAYOUT_DRL_COARSEN
with IGRAPH_LAYOUT_DRL_DEFAULT.