I found 2 000 000 valid puzzles for game 215 but I can't rate them all with SudokuExplainer.
What is the good stategy?
Before final rating with SudokuExplainer, I must choose the good candidates rating them with gsf's sudoku or with skfr?
skfr has been designed to be close enough to serate to help in the pattern game, it is about 100 times faster than serate, but the deviations are sufficient to say that the final validation by serate is compulsory.
The deviation in the rating is most often +-0.1, but can be wider;
I have no personal experience of gsf's sudoku.
In the last games that I searched, I used my last program, skmpp, faster than skfr and performing better in the way I played , but I generate many more puzzle in a game (say 50 to 100 million puzzles for a pattern as in the game 215)
One difficulty is in the fact that at the beginning players are looking for a fast show of diamonds. Later on, you have to play in the holes. Then, you need more or less a pre rating of all puzzles.
My suggestion would be (as did dobrichev) to pre-rate all puzzles unless you really want to win the game, and then to filter the puzzles to rate in serate.
Increasing the chance to win the game push to use a more complex strategy.