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mstemberaandJoost VandeVondele
de24fcebc8
This fixes an old issue where we want to make a position unique but only change a small number of bits in the key instead of all 64 of them randomly. This is fragile and can lead to non uniqueness issues in the TT. Key make_key(uint64_t seed) takes any integer and produces a unique random 64 bit key. It is computationally efficient and is based on a congruential pseudo random number generator using well tested constants by Donald Knuth (see https://en.wikipedia.org/wiki/Linear_congruential_generator) STC https://tests.stockfishchess.org/tests/view/5ef6c78f761b685b4c724bb6 LLR: 2.95 (-2.94,2.94) {-1.50,0.50} Total: 154320 W: 29343 L: 29376 D: 95601 Ptnml(0-2): 2543, 18170, 35891, 17889, 2667 LTC https://tests.stockfishchess.org/tests/view/5ef7d1a9020eec13834a940e LLR: 2.95 (-2.94,2.94) {-1.50,0.50} Total: 53488 W: 6629 L: 6584 D: 40275 Ptnml(0-2): 372, 4878, 16183, 4955, 356 closes https://github.com/official-stockfish/Stockfish/pull/2773 bench: 4626776