This is an interesting idea, but the authors lose credibility by using Crafty as an opponent. Crafty isn't even among the top 30 current programs. Depending on which rating list you reference Crafty is 300 to 400 points worse than Stockfish.

>Crafty has successfully participated in numerous WCCCs, and is a direct descendant of Cray Blitz, the WCCC winner of 1983 and 1986.

That is some pretty weak sauce. "successfully participated"? Is that really worth mentioning? Also Crafty isn't exactly the direct descendant of Cray Blitz even though they were both written by the same person. And while Cray Blitz did win a World Championship some 30 years ago, it did so on the power of its hardware, not the strength of its software. It was running on a Cray supercomputer at a time when other programs were running on vastly inferior hardware. Rebel, who finished one point behind Cray Blitz, was running on a 6502.

Section 5.1, where they show diagrams on moves made by DeepChess is only meaningful if other programs miss the moves.

>This property has been associated with human grandmasters, and has always been considered an area in which computer chess programs were lacking.

But...

In the Aronian game Stockfish running in the browser (PNACL) finds the move Re5 in less than a second.

In the Alekhine game Stockfish finds the move d5 in about 2.5 seconds.

In the Seirawan game Stockfish finds the move c5 in about 1 second.

So while I find the idea interesting I'd like to see more intellectual honesty in this type of paper.