When does a chess engine blow up?

[benstoker]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?

[Dann Corbit]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?;
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I've seen it happen.
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b) does it reach a maximum ply and stop?;
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Sometimes within one second (e.g. a tablebase hit).
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c) does the search become pointless after a certain amount of time?;
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If it already found the right answer, from that point forward additional search has little value.
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d) would a 7 day search be better than a 1 hour search?;
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Yes, unless it is worse.
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e) does anybody do this?
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I have run many thousands of searches, anywhere from one second to one week in duration.
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Could you even let an engine search a single position for a month, a year?

Sure, why not.

[Michael Sherwin]

A well designed engine that has arrays long enough can search for 10's of billions of years (given immortal hardware and a young star to power it) with out crashing. I would imagine that if TSCP were able to search 100 ply deep with out crashing that it would take at least that long to finish.

[bob]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

[benstoker]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

Begs the question: so how long do you estimate it would take crafty to crunch 60 ply from the start position on your super duper computer?

[mcostalba]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

Begs the question: so how long do you estimate it would take crafty to crunch 60 ply from the start position on your super duper computer?

From start position it will take forever, not only Crafty but any engine...

You can reach big depths only in very simple positions with few pieces, typically endgame positions.

[Roman Hartmann]

It also depends on some rather trivial stuff like how you implement the 'search forever'-part.
Some engines will just add a huge number to the current time and stop the search if that time is reached. depending on how big that number is, the search might terminate after a few hours/days already.

Some of my old versions behave like that, they just stop after a few hours of search ...

best regards
Roman

[jwes]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

Begs the question: so how long do you estimate it would take crafty to crunch 60 ply from the start position on your super duper computer?

A fast machine might get to ply 16 in 1 second. Assuming that each ply takes twice as long as the previous ply, 60 ply would take 2^44 seconds or about 524,000 years. It would likely take much longer because when the hash table is way overfilled move ordering suffers badly.

[benstoker]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

Begs the question: so how long do you estimate it would take crafty to crunch 60 ply from the start position on your super duper computer?

A fast machine might get to ply 16 in 1 second. Assuming that each ply takes twice as long as the previous ply, 60 ply would take 2^44 seconds or about 524,000 years. It would likely take much longer because when the hash table is way overfilled move ordering suffers badly.

It appears that one would then get the "best" pv out of any given engine on good hardware after about a day of crunching. After that, it's a waste of time. Is that about right?

[bob]

If you left a chess engine - stockfish for example - running for an entire week analyzing a single position, let's say the start position, a) does is blow up?; b) does it reach a maximum ply and stop?; c) does the search become pointless after a certain amount of time?; d) would a 7 day search be better than a 1 hour search?; e) does anybody do this?

Could you even let an engine search a single position for a month, a year?[/quote

Crafty has always had a max depth. Once it completes 60 plies, it will stop the search no matter what time control is being used, because going deeper would begin to run into array bound conditions. Inside the search, no single branch can go beyond 64 plies since that is an absolute limit, again imposed by array bounds, and this is checked at the top of any search call.

Good code _never_ crashes or hangs.

Begs the question: so how long do you estimate it would take crafty to crunch 60 ply from the start position on your super duper computer?

If you assume depth=20 is one second, to get to 60 with an effective branching factor of 2 would take 2^40 seconds. Which is 1 trillion seconds or about 35,000 years. Probably won't happen.