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Siddhartha Gadgil
Works at Indian Institute of Science
Attended California Institute of Technology
Lives in Bangalore
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Siddhartha Gadgil

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A computer cracks the Boolean Pythagorean triples problem — but is it really maths?
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No, it's not.
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From The Economist Espresso: Foolish Fathers: Trump spells it out

http://econ.st/1ZN1E5R
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Been waiting for quanta magazine to write about alphago
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Interesting! Thanks for the post.
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Revenge of the humans

After losing the first three, Lee Sedol won his 4th game against the program AlphaGo!

Lee was playing white, which for go means taking the second move. So, he was on the defensive at first, unlike the previous game, where he played black.

After the first two hours of play, commenter Michael Redmond called the contest "a very dangerous fight.” Lee Sedol likes aggressive play, and he seemed to be in a better position than last time.

But after another 20 minutes, Redmond felt that AlphaGo had the edge. Even worse, Lee Sedol had been taking a long time on his moves, so had only about 25 minutes left on his play clock, nearly an hour less than AlphaGo. Once your clock runs out, you need to make each move in less than a minute!

At this point, AlphaGo started to play less aggressively. Maybe it thought it was bound to win: it tries to maximize its probability of winning, so when it thinks it's winning it becomes more conservative. Commenter Chris Garlock said “This was AlphaGo saying: ‘I think I’m ahead. I’m going to wrap this stuff up. And Lee Sedol needs to do something special, even if it doesn’t work. Otherwise, it’s just not going to be enough.”

On his 78th move, Lee did something startling.

He put a white stone directly between two of his opponent's stones, with no other white stone next to it. You can see it marked in red here. This is usually a weak type of move, since a stone that's surrounded is "dead".

I'm not good enough to understand precisely how strange this move was, or why it was actually good. At first all the commenters were baffled. And it seems to have confused AlphaGo. In the 87th move, AlphaGo placed a stone in a strange position which commentators said was "difficult to understand."

"AlphaGo yielded its own territory more while allowing its opponent to expand his own," said commentator Song Tae-gon, a Korean nine-dan professional go player. "This could be the starting point of AlphaGo's self-destruction."

Later AlphaGo placed a stone in the bottom left corner without reinforcing its territory in the center. Afterwards it seemed to recover, which Song said would be difficult for human players under such pressure. But Lee remained calm and blocked AlphaGo's attacks. The machine resigned on the 180th move.

Lee was ecstatic. "This win cannot be more joyful, because it came after three consecutive defeats. It is the single priceless win that I will not exchange for anything."

"AlphaGo seemed to feel more difficulties playing with black than white," he said. "It also revealed some kind of bug when it faced unexpected positions."

Lee has already lost the match, since AlphaGo won 3 out of the 5 games. But Lee wants to play black next time, and see if he can win that way.

You can play through the whole game here:

http://eidogo.com/#xS6Qg2A9

Even if you don't understand go, it has a certain charm.

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The cost of a proof

A rough calculation to see how expensive it would be to do the computation for the world's largest proof:

* On the google compute engine, a preemptible processor costs $0.015 per hour
* So 800 processors (which is the number used for this computation) cost $12 per hour. (I assume that the processors in the two cases have roughly the same power).
* The computation ran for two days, say 50 hours.
* Total cost estimate : $600

Of course one has to add storage etc, but still the cost is quite reasonable - even in India about two months stipend of a research student.


A computer cracks the Boolean Pythagorean triples problem — but is it really maths?
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Jayant Vaidya's profile photo
 
How much would it have cost 25, 50 and 100 years ago? Or was it not possible it relevant then?
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Leicester City’s success should be celebrated, but not sentimentalised
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4-1 alphago.
 
The 5 game match between AlphaGo and Lee Sedol has come to an end, with AlphaGo winning the match 4 games to 1. Check out this article by +The Verge which summarizes how the series played out over the last week. For a more detailed rundown of each game, visit the Google Asia Pacific blog at http://goo.gl/cPlksO
Reporting from South Korea on AlphaGo’s matches against Go genius Lee Se-dol over the past week and a half has been intense and fascinating. I’ve written about the results of each game, how Google...
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Google’s AI has won a second contest against Go grandmaster Lee Sodel.
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Have him in circles
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IADERSH V K's profile photo
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Mathematics (Low-dimensional topology), but trying to make computers make my job obsolete.
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  • Indian Institute of Science
    Professor, present
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  • California Institute of Technology
    Ph.D.(Mathematics)
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