The SMP playing style version
During the years (from the last REBEL version of 2003 on after my retirement and withdrawl from the competition while moving to the free ProDeo as a hobby) a lot has changed in the ProDeo search part. It were interesting times, the rise of a new generation in the 2005/6 period, Fruit, Zappa, Rybka, they took the old generation by surprise and quickly as well. Lots of new search ideas.
I still like(d) to follow the developments, understand the new ideas and sometimes try them to satisfy my curiosity. And so during the years I finally moved to full nullmove (giving up my own invented selective search which I used since 1984), rewrote futility pruning up to 6 plies, added LMR and it gave what it promised, elo.
However, I noticed a downside I disliked very much, the quality of the playing style went down. With all those reductions and pruning techniques (you need them to survive) you also cut in the chess knowledge as a result. I tried ways to fix this (which actually was surprisingly simple) but found out the elo loss that came with it was too big. I wanted a system that played more attractive without loss of elo.
I found the solution in using an extra core. Not the usual SMP approach to speed up the search, but the launch of a slightly different ProDeo engine running as slave in the background thinking about the same position but with a different (more spectulative) style. And when the slave reports another move that is clearly better (higher score) then the move of the slave is played.
Clearly better is defined and controlled by 2 parameters in the default ProDeo.eng