aggregation readout layer

The aggregation readout layer is a readout layer given by

where $C\in {\mathbb{R}}^{d_L\times d}$ and $\text{aggr}:{\mathbb{R}}^{n\times d}\to {\mathbb{R}}^{1\times d}$ is node-level aggregation

Typical aggregation functions are the mean, sum, max, min, median, etc

• this is now independent of $n$ (my aggregation functions don't change based on the size of my graph)
• permutation invariant since the aggregation functions are also permutation invariant
• this remains transferrable across graphs, unlike the fully connected readout layer