About St John Grimbly

Hi everyone! I'm St John, a MSc Applied Mathematics student at UCT (collaboration with InstaDeep). I'm currently working on improving the reasoning of multi-agent reinforcement learning agents with a special focus on causality. You can find some of my posts on mathemafrica.org or stjohngrimbly.com. Pop a message if you're interested in chatting!

Preliminaries for CRL

In the previous blog post we discussed and motivated the need for a causal approach to reinforcement learning. We argued that reinforcement learning naturally falls on the interventional rung of the ladder of causation. In this blog post we’ll develop some ideas necessary for understanding the material covered in this series. This might get quite technical, but don’t worry. There is still always something to take away. Let’s begin.

This Series

  1. Causal Reinforcement Learning
  2. Preliminaries for CRL
  3. Coming soon


As you probably recall from high school, probability and statistics are almost entirely formulated on the idea of drawing random samples from an experiment. One imagines observing realisations of outcomes from some set of possibilities when drawing from an assortment of independent and identically distributed (i.i.d.) events. In reality, this assumption of i.i.d. events fails in many situations. Consider shifting some distribution of events or intervening in the system. This failure of an often fundamental assumption in statistics is one reason for the causal approach we shall develop.…

By | April 6th, 2021|Background, English, Level: Simple|1 Comment

Causal Reinforcement Learning: A Primer

As part of any honours degree at the University of Cape Town, one is obliged to write a thesis ‘droning’ on about some topic. Luckily for me, applied mathematics can pertain to pretty much anything of interest. Lo and behold, my thesis on merging causality and reinforcement learning. This was entitled Climbing the Ladder: A Survey of Counterfactual Methods in Decision Making Processes and was supervised by Dr Jonathan Shock.

In this series of posts I will break down my thesis into digestible blog chucks and go into quite some detail of the emerging field of Causal Reinforcement Learning (CRL) – which is being spearheaded by Elias Bareinboim and Judea Pearl, among others. I will try to present this in such a way as to satisfy those craving some mathematical detail whilst also trying to paint a broader picture as to why this is generally useful and important. Each of these blog posts will be self contained in some way.…

By | February 3rd, 2021|Background, English, Level: intermediate, Level: Simple|1 Comment