[igraph] speed slowdown with version change

[Robin Cowan]

I have a small simulation that creates a network of agents who then play a game 
on the network.
I noticed that when I run the simulation under R 3.1.3 igraph 0.7.1 it takes 
about 4 seconds.
When I run it using R 3.5.1 with igraph 1.2.2 it takes about 4 minutes.

I use igraph to create a network and then extract neighbourhoods. The 
neighbourhoods are what is actually used  to get the nodes to play the game. 
I re-wrote it to remove igraph from the code — to test whether igraph is the 
issue, I created a list directly which represented the neighbourhoods.
With that elimination of igraph (and no other changes) it takes about 4 seconds 
under R 3.5.1
Some of the maintainers on the R list looked and came tot he same conclusion. 
The problem is with igraph changes between 0,7 and 1.2.
Has this come to light before?

Thanks,
Robin Cowan