Playing strength first, I collected a number of changes during the last 4 years resulting in a ~35 elo improvement. ~20 elo came from a new idea replacing IID with what I called IIR. A number of other engines (among them Stockfish) adopted the idea.
Polyglot opening books, improved the standard ProDeo opening book with +46 elo, see elsewhere. Created additional books with new options, an overview:
Stockfish 12 at depth 20
Made from 2700+ elo rated human games.
Stockfish 12 at depth 16
Searched when the ProDeo book fails to produce a move.
Average depth 24.35
Made from 48.713 Stockfish 12 games.
Fun book with all the great players of the 19th and early 20th century.
maintained in the book.ini file
[Book File = books\ProDeo.bin]
First book ProDeo will search.
[Book Two = books\usb.bin]
Second book ProDeo will search if first book fails.
[Book Depth = 80]
Maximum plies ProDeo will search books.
[Book Use = vary]
User priority preference, there are 3 options -
vary - Play varied based on the weight, see one of the 4 screenshots.
score - Play the move with the highest Stockfish 12 score.
learn - Play the move with the highest learn value.
[WDL Factor = 250]
Randomize the book, in a nutshell, a low value makes a book very random, a high value narrows the book. The following example makes the effect visible and note what happens to the weights of the big-four 1. e4 | 1. d4 | 1. Nf3 | 1. c4
Unzip the archive somewhere on your hard drive.
ProDeo 3.0 (Winboard and UCI compatible) which you can run in multiple Interrfaces, among them the freeware Arena.
To run ProDeo you will need to announce the engine first.
Used PGN - EPD collections