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Mastering the Game of Go with Deep Neural Networks and Tree Search

Nature, 2016 · paper · AI and machine learning

Describes a Go-playing program that combines deep neural networks for evaluating positions and selecting moves with tree search. The networks are trained through supervised learning from expert games and reinforcement learning from self-play.

Checked: PDF from storage.googleapis.com, fetched 4 Oct 2026. Page numbers are those of that PDF.

10 findings

Substance Methods give p(a beats b) = 1/(1 + exp(celo(e(b) − e(a))) with "the standard constant celo = 1/400", which yields 64% for a 230-point gap, not the "79% probability of winning" stated in the Fig. 4 caption; 79% needs base 10 (or celo = ln(10)/400).
  • p. 8 Methods, Evaluation
    computed by the BayesElo program37 using the standard constant celo = 1/400
  • p. 4 Figure 4 caption
    a 230 point gap corresponds to a 79% probability of winning

Only the authors can say what is right here.

Judge's note: Page 8 crop shows the formula with exp and celo = 1/400; page 4 crop shows 'a 230 point gap corresponds to a 79% probability of winning'. exp(−230/400) = exp(−0.575) ≈ 0.5627, giving 1/(1+0.5627) = 0.640. 10^(−0.575) ≈ 0.2661, giving 1/(1+0.2661) = 0.790. So the caption follows the base-10 Elo formula and the printed Methods formula does not reproduce it. Nothing elsewhere in the paper redefines celo. The denominator also appears to be missing a closing parenthesis. Either the base or the constant is misprinted; authors to say which.

Second check: another model agreed · checked by hand

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Reference or label Methods: "Fig. 2b and Extended Data Table 3 additionally show the results of training with k = 128, 256 and 384 filters"; the filter-count comparison is Fig. 2a, not Fig. 2b.
  • p. 8 Methods, Neural network architecture
    Fig. 2b and Extended Data Table 3 additionally show the results of training with k = 128, 256 and 384 filters
  • p. 2 Figure 2 caption
    a, Plot showing the playing strength of policy networks as a function of their training accuracy. Policy networks with 128, 192, 256 and 384 convolutional filters per layer
  • p. 8
    Fig. 2b and Extended Data Table 3 additionally show the results
  • p. 8 Methods, Neural network architecture
    Fig. 2b and Extended Data Data Table 3 additionally show the results of training with k = 128, 256 and 384 filters

Judge's note: Page 8 crop confirms the sentence as quoted (the 'Data Data' variant is a reviewer transcription slip). Page 2 image: panel a's legend lists 128, 192, 256 and 384 filters and the caption says so; panel b plots mean squared error of the value network versus rollout policies by move number and has no filter-count data. The main text on page 2 correctly cites Fig. 2a. The missing 384 row in Extended Data Table 3 is handled in C021.

Second check: another model agreed

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Reference or label Reference "27. Sutton, R. & Barto, A. Reinforcement Learning: an Introduction (MIT Press, 1998)." is never cited; citations go from "(RL)25,26" to "players28–30".
  • p. 6 Reference list, entry 27
    27. Sutton, R. & Barto, A. Reinforcement Learning: an Introduction (MIT Press, 1998).
  • p. 3 Reinforcement learning of value networks
    tion s of games played by using policy p for both players28–30

Only the authors can say what is right here.

Judge's note: Reference 27 is in the list on p6. Searched the whole extracted text for a citation of 27, alone or inside a range: the citation groups are 13–15, 21–24, 25,26, 28–30, 28,29,47, 24,28,29 and so on, and none covers 27; every other "27" in the text is a move number in a figure or a table value. Checked p2 (25,26) and p3 (28–30) on the images. A citation was probably lost; the authors must say where it belongs.

Second check: another model agreed

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Reference or label Reference 16: "In 17th International Conference on Machine Learning, 273–280 (2007)." The list's other ICML entries (11th in 1994, 26th in 2009, 32nd in 2015) make the 2007 conference the 24th.
  • p. 6 Reference list, entry 16
    In 17th International Conference on Machine Learning, 273–280 (2007).
  • p. 6 Reference list, entry 24
    In 32nd International Conference on Machine Learning, 1766–1774
  • p. 9 Reference list, entry 51
    In 26th International
  • p. 9 Reference 39
    In 11th International Conference on Machine Learning, 157–163

Judge's note: Read refs 16 and 24 on p6 and refs 39 and 51 on p9. All three other entries fit ordinal = year - 1983, so 2007 gives 24th, not 17th. The inference is internal to the reference list (it assumes one conference a year, which the three entries are consistent with). The image shows "17th", so it is not an extraction artefact.

Second check: another model agreed

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Reference or label Methods, Expansion: "The new node is initialized to {N(s′, a) = Nr(s′, a) = 0, W(s′, a) = Wr(s′, a) = 0, P(s′,a) = pσ(a|s′)}, using a tree policy pτ(a|s′) ... to provide placeholder prior probabilities"; the initial prior should be pτ, since pσ only arrives later ("these replace the placeholder prior probabilities, P(s′, a) ← pσβ(a|s′)").
  • p. 7 Methods, Search algorithm, Expansion (Fig. 3b)
    P(s′,a) = pσ(a|s′)}, using a tree policy pτ(a|s′)
  • p. 7 Methods, Expansion, later sentence
    these replace the placeholder prior probabilities

Judge's note: Read the passage on the p7 image and the crop: the subscript in the initialisation is σ and the tree policy is pτ. The same paragraph says the tree policy supplies placeholder priors and that the SL policy network output replaces them after asynchronous GPU evaluation; the distributed-search paragraph and the Extended Data Table 7 legend ("placeholder probabilities from the tree policy pτ") say the same. So the initialisation as printed contradicts the surrounding description; the evident reading is P(s′,a) = pτ(a|s′). A symbol error; the described algorithm is clear from the text.

Second check: another model agreed

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Reference or label Extended Data Table 3 caption says "using only the first 4, 12 or 20 input feature planes listed in Extended Data Table 1". The input feature planes are listed in Extended Data Table 2; Extended Data Table 1 is "Details of match between AlphaGo and Fan Hui".
  • p. 12 Extended Data Table 3 caption
    20 input feature planes listed in Extended Data Table 1
  • p. 10 Extended Data Table 1 title
    Details of match between AlphaGo and Fan Hui
  • p. 11 Extended Data Table 2 title
    Input features for neural networks
  • p. 12
    input feature planes listed in Extended Data Table 1.

Judge's note: Read the ED Table 3 caption on p12 in the image. ED Table 1 (p10) lists the Fan Hui match games: date, colours, category, result. ED Table 2 (p11) is titled 'Input features for neural networks'. The main text (text-layer lines 77 and 2563) cites ED Table 2 for the input features. The first 4, 12 and 20 planes match ED Table 2's rows (3+1=4, +8=12, +8=20). The caption pointer is wrong.

Second check: another model agreed

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Reference or label Footnotes of Extended Data Tables 6 and 9 say "CN4, ZN4 and PC4 were given 4 handicap stones", but the handicap CrazyStone entry is labelled CS4 in both tables; "CN4" should be "CS4".
  • p. 15 Extended Data Table 6 caption
    CN4, ZN4 and PC4 were given 4 handicap stones
  • p. 15 Extended Data Table 6, Short name column
    CS4
  • p. 15
    CN4, ZN4 and PC4 were given 4 handicap stones;
  • p. 18 Extended Data Table 9 footnote
    CN4, ZN4 and PC4 were given 4 handicap stones

Judge's note: Page 15 image: rows are CS4, ZN4, PC4 and the footnote reads CN4. Page 18 crop: row label CS4, footnote CN4 again. No program is abbreviated CN anywhere.

Second check: another model agreed

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Reference or label The Extended Data Table 7 caption gives the same program list twice: "either using the policy network pσ(αrvp, αvp, αrp), or no policy network (αrvp, αvp, αrp)". According to the table body, the programs with no policy network ([pτ]) are αrv, αv and αr.
  • p. 16 Extended Data Table 7 caption
    either using the policy network pσ(αrvp, αvp, αrp), or no policy network (αrvp, αvp, αrp)
  • p. 16 Extended Data Table 7, Policy network column
    [pτ]
  • p. 16
    or no policy network (αrvp, αvp, αrp)
  • p. 16 Extended Data Table 7 footnote
    or no policy network (αrvp, αvp, αrp), that is, instead using the placeholder probabilities from the tree policy pτ throughout

Judge's note: Read the subscripts in the caption image on p16: both lists clearly read αrvp, αvp, αrp. In the table, the rows αrv, αv and αr have [pτ] in the Policy network column, and αrvp, αvp and αrp have pσ. So the second list should be (αrv, αv, αr). This is a labelling error in the caption; the data are fine.

Second check: another model agreed

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Reference or label Extended Data Table 9 footnote reads "CN4, ZN4 and PC4 were given 4 handicap stones", but the table row for CrazyStone with four handicap stones is labelled CS4 (and the no-handicap row is CS); "CN4" should be "CS4".
  • p. 18 Extended Data Table 9 caption
    CN4, ZN4 and PC4 were given 4 handicap stones
  • p. 18 Extended Data Table 9, row labels
    CS4
  • p. 18
    CN4, ZN4 and PC4 were given 4 handicap stones;

Judge's note: Viewed the crop and the full page 18 image. Row labels are CS, ZN, PC, FG, GG, CS4, ZN4, PC4; there is no CN row or program abbreviated CN anywhere in the table. The footnote clearly prints CN4 in italics with subscript 4. The text layer shows the same label mismatch in the Extended Data Table 6 caption (CS4 row, CN4 in caption), so this is a repeated caption typo, not an extraction artefact. Rated S2 as a wrong label in a caption; the data are unaffected and the intended meaning is evident.

Second check: another model agreed

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Wording Expansion step initialises "{N(s′, a) = Nr(s′, a) = 0, W(s′, a) = Wr(s′, a) = 0, P(s′,a) = pσ(a|s′)}", but the edge statistics defined just above are "{P(s, a), Nv(s, a), Nr(s, a), Wv(s, a), Wr(s, a), Q(s, a)}"; the un-subscripted N and W should read Nv and Wv.
  • p. 7 Methods, Expansion (Fig. 3b)
    {N(s′, a) = Nr(s′, a) = 0, W(s′, a) = Wr(s′, a) = 0
  • p. 7 Methods, Search algorithm, edge statistics
    {P(s, a), Nv(s, a), Nr(s, a), Wv(s, a), Wr(s, a), Q(s, a)}

Judge's note: Read page 7 image. The search-algorithm paragraph defines only Nv, Nr, Wv, Wr; the backup paragraph updates Nv/Wv and Nr/Wr. The expansion line pairs un-subscripted N, W with Nr, Wr and never initialises Nv, Wv, so the subscript v was dropped. Notation slip; meaning recoverable.

Second check: another model agreed

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8 minor (typos and the like; most checked by the judge only)
Wording Selection picks in-tree actions "At each of these time steps, t < L" and rollouts act "t ≥ L", but backup updates edges "At each in-tree step t ≤ L"; the index ranges overlap at t = L.
  • p. 7 Methods, Selection (Fig. 3a)
    At each of these time steps, t < L, an action is selected according to the statistics
  • p. 7 Methods, Backup (Fig. 3d)
    At each in-tree step t ≤ L of the simulation
  • p. 7 Methods, Evaluation (Fig. 3c)
    At each of these time-steps, t ≥ L, actions are selected by both players accord

Judge's note: Read page 7 image and crop. Selection uses t < L, evaluation t ≥ L, and backup three times says t ≤ L. The edge (sL, aL) is chosen by the rollout policy and is not a tree edge, so t ≤ L is loose. Could be a convention that counts the leaf step; minor inconsistency, not a wrong result.

Second check: another model agreed

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Wording Methods: "Fig. 2b and Extended Data Table 3 additionally show the results of training with k = 128, 256 and 384 filters", but Extended Data Table 3 has only 128, 192 and 256 filters ("128, 192 or 256 filters"); 384 appears only in Fig. 2a.
  • p. 8 Methods, Neural network architecture
    Extended Data Table 3 additionally show the results of training with k = 128, 256 and 384 filters
  • p. 12 Extended Data Table 3 caption and Filters column
    The policy network architecture consists of 128, 192 or 256 filters in convolutional layers

Judge's note: Page 12 image: the Filters column contains only 128, 192 and 256, and the caption says the same. The sentence can be read collectively (figure and table together cover 128, 256 and 384, with 384 in the figure only), so this is a loose statement and not a clear error. Distinct from the Fig. 2b/2a pointer in C020.

Second check: another model agreed

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Typo Methods: "asynchronous stochastic gradient descent update to maximize the log likelihood of the action", whereas the main text says "stochastic gradient ascent to maximize the likelihood"; the update shown (Δσ = (α/m) Σ ∂log pσ/∂σ) is an ascent step.
  • p. 8 Methods, Policy network: classification
    gradient descent update to maximize the log likelihood of the action
  • p. 2 Supervised learning of policy networks
    using stochastic gradient ascent to maximize the likelihood of the human move

Judge's note: Page 8 crop and page 2 image confirm both wordings. 'SGD' is commonly used generically for either direction, and the printed update is unambiguous, so this is a terminology inconsistency only.

Second check: none (judge only)

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Typo Reference 29 ends with a stray number: "In 10th Advances in Computer Games Conference, 97–108 (2003). 267."
  • p. 6 Reference list, entry 29
    In 10th Advances in Computer Games Conference, 97–108 (2003). 267.
  • p. 6 Reference 29
    97–108 (2003). 267.

Judge's note: Page image p6 shows "267." printed after the year of reference 29. The page range is already given as 97–108, and no other entry has such a trailing number.

Second check: none (judge only)

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Typo Reference 8: "In Advances in Neural Information Processing, 1068–1074 (1996)." lacks "Systems"; refs 17, 26, 43 and 61 give "Advances in Neural Information Processing Systems".
  • p. 6 Reference list, entry 8
    In Advances in Neural Information Processing, 1068–1074 (1996).
  • p. 6 Reference list, entry 26
    In Advances in Neural Information Processing Systems, 1057–1063 (2000).
  • p. 6 Reference 17
    In Advances in Neural Information Processing

Judge's note: Read ref 8, 17 and 26 on p6 and refs 43 and 61 on p9. In ref 8 the title is followed directly by the page range, so the word is missing in print, not lost at a line break.

Second check: none (judge only)

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Typo Reference 21: "In International Conference of Machine Learning, 873–880 (2006)." has "of" where refs 16, 24, 39 and 51 have "International Conference on Machine Learning".
  • p. 6 Reference 21
    In International Conference of Machine Learning,

Judge's note: Read ref 21 on the p6 image: it prints "Conference of Machine Learning". The other four entries for the same conference use "on" (p6 and p9). Cosmetic.

Second check: none (judge only)

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Typo Stray space: "At the end of the simulation, t he rollout statistics are updated" should read "the rollout statistics".
  • p. 7 Methods, Backup (Fig. 3d)
    At the end of the simulation, t he rollout statistics are

Judge's note: The gap inside 'the' is visible in the crop of page 7 (Backup paragraph), not just in the text layer.

Second check: none (judge only)

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Typo Extended Data Table 2 spells the first feature "Stone colour" and the last "Player color".
  • p. 11 Extended Data Table 2, last row
    Player color
  • p. 11 Extended Data Table 2, first row
    Stone colour

Judge's note: Both spellings are visible in the page 11 image, in the same table. Cosmetic.

Second check: none (judge only)

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