Search found 3989 matches

by syzygy
Tue Jun 18, 2019 11:25 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: strange code for tt
Replies: 3
Views: 221

Re: strange code for tt

Any insights? What happens when you store MOVE_NONE? Does that delete the old tt move (if there was one for the current position)? It is correct not to store the new "best" move if you haven't actually found a move that is better than start_alpha, but you should not delete the old tt move if there ...
by syzygy
Tue Jun 18, 2019 9:13 pm
Forum: Computer Chess Club: General Topics
Topic: is this an issue with missing DTZ ?
Replies: 6
Views: 254

Re: is this an issue with missing DTZ ?

syzygy wrote:
Tue Jun 18, 2019 7:45 pm
But none of the June 9 patches seem to relate to the relevant code.
I overlooked that this patch makes changes to "tbRank" in search.cpp and search.h. So that must be the problem. Should be happening in 6-piece positions too, I guess.
by syzygy
Tue Jun 18, 2019 7:45 pm
Forum: Computer Chess Club: General Topics
Topic: is this an issue with missing DTZ ?
Replies: 6
Views: 254

Re: is this an issue with missing DTZ ?

So with multiPV=5 Stockfish is showing 5 moves that lose, lose, draw, lose, lose in that order? That's pretty weird... It is correct that Kc5 draws and all other moves lose: https://syzygy-tables.info/?fen=2b5/8/3k3p/P7/8/3K1BP1/8/8_b_-_-_0_1 Of course it should not play a move that is known to lose...
by syzygy
Sun Jun 16, 2019 7:01 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: strategies for finding slowdows in lazy smp
Replies: 26
Views: 1003

Re: strategies for finding slowdows in lazy smp

Now my question is: what are strategies for finding what causes this slow down? The threads share no common variables apart from the transposition table. That tt has no locks, it uses the xor-trick. Most likely the threads share common cache lines, which has the same effect as sharing common variab...
by syzygy
Thu Jun 13, 2019 10:57 pm
Forum: Computer Chess Club: General Topics
Topic: Widely unknown pioneering chess "paper machine" by Gunter Sсhliebs
Replies: 9
Views: 560

Re: Widely unknown pioneering chess "paper machine" by Gunter Sсhliebs

G. Schlieb referred Shannon's groundbreaking paper, which is surely the base his paper. It has the same board represention (same piece codes), evaluation function and similar search ideas concerning selectivity and quiescence. And these are by far not the only similarities between the two papers. O...
by syzygy
Thu Jun 13, 2019 9:57 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: strategies for finding slowdows in lazy smp
Replies: 26
Views: 1003

Re: strategies for finding slowdows in lazy smp

Now my question is: what are strategies for finding what causes this slow down? The threads share no common variables apart from the transposition table. That tt has no locks, it uses the xor-trick. Most likely the threads share common cache lines, which has the same effect as sharing common variab...
by syzygy
Sun Jun 09, 2019 11:11 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Hash collision?
Replies: 42
Views: 1458

Re: Hash collision?

Collisions in the sense of two positions mapping to the same entry are unavoidable. They cannot cause strang evals and moves as long as the engine detects them as different. So what is important is the ability of the engine to detect that two different positions mapping to the same entry/bucket are...
by syzygy
Sun Jun 09, 2019 11:08 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Hash collision?
Replies: 42
Views: 1458

Re: Hash collision?

In Stockfish, the ratio of false hits is one in every 2^16/3 = 21845 probes, so one in every 16384 is unlikely to do a lot of damage. Maybe Stockfish doesn't probe on every node (position) it generates, I don't know. But if it does, and you run on a fairly modern PC it can have like 1000 false hits...
by syzygy
Sat Jun 08, 2019 12:51 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Hash collision?
Replies: 42
Views: 1458

Re: Hash collision?

So.. going back to my original posting, here's my data. What do people think about the probability of hash collisions causing strange evals and moves? 1. Time control 40 moves in 25 minutes 2. Searching approx 2 million NPS 3. Size of hash table, 2097152, with 4 buckets 4. Using a 64 bit int for th...
by syzygy
Sat Jun 01, 2019 7:15 pm
Forum: Computer Chess Club: General Topics
Topic: for kai laskos (about doubling speed elo gain)
Replies: 14
Views: 882

Re: for kai laskos (about doubling speed elo gain)

Isn't it to be expected that the draw rate will be lower (and so the W/L will be higher) between the same two engines as TC increases? Both engines will make fewer mistakes and there will therefore be less noise. At STC, mistakes by both engines cancel each other out so far as they don't represent ...