Traditional algorithms
The neural network, Google says, outperforms human and industry automated tool placement.
So when you see in the article "beats humans" read it as "beats humans using their brains and their automated tools". I'll try to make that clearer.
Google's argument is that the neural net places macro blocks better than humans and their tools, and does it in hours, and not in a process that can take months to juggle around blocks and cells. Also, the AI can place the blocks in an unconventional manner: it seems to scatters them as needed, which some humans might not be so brave to do. The design looks like a mess but it's optimal.
FWIW it's been 15+ years since I've done any kind of chip design. In researching this piece, I read a pre-publication analysis of the paper by Andrew B. Kahng, a VLSI professor at UCSD, and for instance he mentions:
"The authors report that the agent places macro blocks sequentially, in decreasing order of size — which means that a block can be placed next even if it has no connections (physical or functional) to previously placed blocks.
"When blocks have the same size, the agent’s choice of the next block echoes the choices made by ‘cluster-growth’ methods, which were previously developed in efforts to automate floorplan design, but were abandoned several decades ago.
"It will be fascinating to see whether the authors’ use of massive computation and deep learning reveal that chip designers took a wrong turn in giving up on sequential and cluster-growth methods."
In other words, the AI works differently to humans and their automated tools, and that difference can be seen.
C.