Just upgraded to Ubuntu 18.04 and can't use compiz grid window resize commands?
Solution 1:
Ubuntu 18.04 dropped support for the Unity desktop compositor in favour of GNOME Shell. GNOME Shell is incompatible with Compiz. You need to look for a method to replicate this behaviour using GNOME Shell and its extensions or install and use an unofficial, community-supported version of Unity.
P.S.: There's a follow-up question with a suggestion for a replacement GNOME Shell extension.
Solution 2:
Here you can find the appropriate GNOME extension: https://extensions.gnome.org/extension/39/put-windows/