I'm reading 'An Algorithm for Subgraph Isomorphism(Ullmann, 1974)'
which was referenced by 'Network Motif Discovery Using Subgraph
Enumeration and Symmetry-Breaking(Grochow and Kellis)'.
It's a bit interesting to read this line:
'A parallel asynchronous logic-in-memory implementation of a
vital part of this algorithm is also described, although this hardware has not
actually been built. The hardware implementation would allow
very rapid determination of isomorphism'
Now 30 years have passed,
and Dual-Core and even Quad-Core CPUs are largely in use.
Multi-thread programming is universal nowadays.
I don't know J. R. Ullmann personally,
how old he is... what he is doing now...
but I wonder he is living a better life now.