Neural Architecture Search with Reinforcement Learning
2017 · paper · AI and machine learning
Trains a recurrent network with reinforcement learning to generate neural network designs, rewarding those that score well on validation data. It reports a 3.65% CIFAR-10 test error and a recurrent cell reaching 62.4 perplexity on Penn Treebank.
Checked: PDF from arxiv.org, fetched 4 Oct 2026. Page numbers are those of that PDF.
3 findings
Reference or label The abstract ("achieves a state-of-the-art perplexity of 1.214") and p.9 ("our model achieves 1.214 perplexity") call 1.214 a perplexity, but Table 3 reports it under "Test Bits Per Character".
- p. 1 Abstract, last sentence
achieves a state-of-the-art perplexity of 1.214
- p. 9 Transfer Learning Results
model achieves 1.214 perplexity
- p. 10 Table 3 column header
Test Bits Per Character
- p. 1 Abstract
perplexity of 1.214
Judge's note: Page 10 shows Table 3: the column header is "Test Bits Per Character" and the 16.28M Two Layer with New Cell row reads 1.214. Pages 1 and 9 call the same number a perplexity. Bits per character and perplexity are different metrics, so the metric name is wrong. A per-character perplexity would be 2 raised to the BPC, about 2.32; that cannot be written with + - * / alone, so it is not in the arithmetic list.
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Reference or label In Table 1, the row "DenseNet-BC (L = 100, k = 40) Huang et al. (2016b)" lists Depth 190, which contradicts its own label L = 100.
- p. 7 Table 1, DenseNet-BC row
DenseNet-BC (L = 100, k = 40) Huang et al. (2016b) 190 25.6M 3.46
- p. 7 Table 1, DenseNet-BC row
DenseNet-BC (L = 100, k = 40) Huang et al. (2016b)
Judge's note: Page 7 Table 1 checked. In the three DenseNet rows above, L equals the Depth column (40/40, 100/100, 100/100). This row gives L = 100 but Depth 190, so the label and the column contradict each other within the table. The claim that the 25.6M, 3.46% model is L = 190 rests on outside knowledge of Huang et al.
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Wording Selection rule inverted: "the test perplexity is taken where the validation set perplexity is highest", whereas the preceding paragraph takes the step "where validation set perplexity is the best".
- p. 9 Transfer Learning Results, larger experiment
the test perplexity is taken where the validation set perplexity is highest
- p. 9 Transfer Learning Results, first paragraph
the step where validation set perplexity is the best
- p. 9 Transfer learning, larger experiment
validation set perplexity is highest
Judge's note: Page 9 image, Transfer Learning Results. In the first paragraph the test result is taken at the step with the best validation perplexity. The paragraph on the larger experiment says "highest". Lower perplexity is better, so "highest" would mean the worst checkpoint, and nothing in the paper says the larger experiment used a different protocol. It should probably read "lowest" (or "best").
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16 minor (typos and the like; most checked by the judge only)
Reference or label Two reference entries for the same work: "Gao Huang, Zhuang Liu, and Kilian Q. Weinberger. Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016a." and "Gao Huang, Zhuang Liu, Kilian Q. Weinberger, and Laurens van der Maaten. Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016b."
- p. 12 References
Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016a.
- p. 12 References
Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016b.
- p. 12 References
Gao Huang, Zhuang Liu, and Kilian Q. Weinberger. Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016a.
- p. 12 References
Gao Huang, Zhuang Liu, Kilian Q. Weinberger, and Laurens van der Maaten. Densely connected convolutional networks. arXiv preprint arXiv:1608.06993, 2016b.
Only the authors can say what is right here.
Judge's note: Page 12 image shows both entries with the same title and the same arXiv ID; only the author lists differ. The text and Table 1 cite 2016a for the DenseNet rows and 2016b for DenseNet-BC, so a reader cannot tell which source each points to. The entries are probably meant to be different arXiv versions of one paper, but no version is given. The authors should merge the entries or state the version for each.
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Wording The abstract says "a test error rate of 3.65, which is 0.09 percent better". The 0.09 is a difference in percentage points (3.74 − 3.65), not a relative percent, and 3.65 is printed without a unit.
- p. 1 Abstract
achieves a test error rate of 3.65, which is 0.09 percent better
Judge's note: Page 1 abstract checked. The arithmetic gives 0.09 percentage points. Writing "percent" for percentage points is common loose usage, so this is only a wording point.
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Wording The introduction says "achieves a 3.65 test error, while being 1.05x faster than the current best model". The comparison model is the 3.74% DenseNet, but Table 1 lists DenseNet-BC at 3.46%.
- p. 2 Introduction, paragraph 2
while being 1.05x faster than the current best model
- p. 7 Table 1, DenseNet-BC row
3.46
- p. 8 Section 4.1 Results
1.05x as fast as the DenseNet model that achieves 3.74%
Judge's note: Page 2 has no qualifier. The abstract limits the claim to "the previous state-of-the-art model that used a similar architectural scheme". Section 4.1 (p.8) names the comparison model as the 3.74% DenseNet and explains that the 3.46% DenseNet-BC uses 1x1 convolutions. Without the qualifier the introduction overstates the comparison; the fix is to restore it.
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Wording Section 3.3 says layer N has "N − 1 content-based sigmoids" for the "previous N − 1 anchor points", but then says "j ranges from 0 to N − 1", which gives N values.
- p. 4 Section 3.3
which has N −1 content-based sigmoids
- p. 4 Section 3.3, below the sigmoid equation
ranges from 0 to N −1
Only the authors can say what is right here.
Judge's note: Page 4 checked. If j runs from 0 to N−1 there are N indices, which does not match N−1 sigmoids. The paper says (p.4–5) that the image is used as input when a layer has no input connections, so index 0 is not clearly a separate sigmoid. This is an off-by-one ambiguity in the indexing that only the authors can resolve.
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Wording Page 8 calls the 3.74% model "the best human-invented architecture", but Table 1 and the same paragraph cite a DenseNet at 3.46%.
- p. 8 Section 4.1, third results paragraph
the best human-invented architecture that achieves 3.74%
- p. 8 Section 4.1, same paragraph
The DenseNet model that achieves 3.46% error rate (Huang et al., 2016b)
- p. 7 Table 1
3.46
Judge's note: Pages 7–8 checked. Later in the same paragraph the paper says the 3.46% DenseNet-BC uses 1x1 convolutions and is "not an exact comparison", which partly explains the choice. The phrase "the best human-invented architecture" still has no qualifier.
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Wording Page 8 says 15,000 is "the number of architectures that we allow our controller to evaluate", but the Figure 6 curves ("every 400 models run") run to about 20,800 on the Iteration axis.
- p. 8 Section 4.2, Search space
15,000, the number of architectures that we allow our controller to evaluate
- p. 10 Figure 6 x-axis and caption
every 400 models run
- p. 8 Section 4.2 Search space
much larger than 15,000, the number of architectures that we allow our controller to evaluate
- p. 10 Figure 6 x-axis and caption
random search every 400 models run
Only the authors can say what is right here.
Judge's note: Page 10 Figure 6: the last plotted points sit just above 20,000. The paper does not say how "Iteration" relates to models evaluated; it might count random-search and controller models together. Only the authors can reconcile the two numbers.
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Wording Page 8 says "As stated earlier, this is more challenging because the search space is larger", but nothing earlier says this.
- p. 8 Section 4.1, second results paragraph
As stated earlier, this is more challenging because the search space is larger.
Only the authors can say what is right here.
Judge's note: I searched the text for "stride", "larger" and "challenging". The only earlier mentions of stride are in the Figure 2 caption and the p.7 search-space sentence, and neither says that predicting strides is harder or makes the search space larger. The back-reference has nothing to point to.
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Wording Text says "The results on small settings with 5-6M parameters confirm that the new cell does indeed generalize", but in Table 3 the authors' small LSTM and new-cell models both have 6.57M parameters.
- p. 9 Transfer Learning Results
settings with 5-6M parameters confirm that the new cell does indeed generalize
- p. 10 Table 3, our rows
6.57M
- p. 9 Transfer Learning Results
The results on small settings with 5-6M parameters confirm that the new cell does indeed generalize
Only the authors can say what is right here.
Judge's note: Page 9 text and Table 3 on the page 10 image. In Table 3, Two layer LSTM and Two Layer with New Cell are both 6.57M, outside the stated 5-6M range. Only the Ha et al. rows (4.92M, 5.06M) are near that range. This is a loose approximation rather than a substantive error.
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Wording "the models found by Neural Architecture Search outperform other state-of-the-art models on this dataset", yet Table 2 gives the NAS base-8 model (32M) a test perplexity of 67.9, worse than Zilly et al. (2016) at 66.0.
- p. 9 Section 4.2 Results
the models found by Neural Architecture Search outperform other state-of-the-art models on this dataset
- p. 9 Table 2
67.9
Judge's note: Table 2 on the page 9 image: the NAS rows are 67.9, 64.0 and 62.4, and Zilly et al. is 66.0. Only the two NAS models with shared embeddings beat 66.0, so the general claim overstates for one of the three NAS models. The authors may have meant comparable configurations.
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Wording "SGD with a learning rate of 0.5 until 400K steps. After that the learning rate is annealed by dividing by 2 after every 100K steps until it reaches 0.1": repeated halving of 0.5 never equals 0.1.
- p. 10 GNMT training details
dividing by 2 after every 100K steps until it reaches 0.1
Judge's note: Page 10 image. Halving 0.5 gives 0.25, 0.125, 0.0625, so it never equals 0.1. The sentence most plausibly means 0.1 is a floor (0.25, 0.125, then clipped to 0.1), but the wording leaves the schedule ambiguous. This is a minor clarity point.
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Typo Page 2 reads "predicts hyperparameters one a time"; it should read "one at a time".
- p. 2 Section 2, Related Work, auto-regressive paragraph
predicts hyperpa- rameters one a time
Judge's note: Checked in the Related Work paragraph on the page 2 image: the word "at" is missing.
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Typo Three typos: "does not depend on the on the current action" (p.4), "Not only is our cell is better" (p.9) and "parameter sever" (p.10).
- p. 4 Section 3.2, paragraph after baseline equation
does not depend on the on the current action
- p. 9 Results
Not only is our cell is better
- p. 8 Search space
the search space is has ap-
- p. 2 Related work
one a time
Judge's note: All three are visible on the page images for pp.4, 9 and 10. The cluster also lists "one a time" and "search space is has"; those are judged under C004 and C010.
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Typo Page 8 reads "the search space is has approximately 6 × 10^16 architectures"; "is has" should read "has".
- p. 8 Section 4.2, Search space
the search space is has ap-
Judge's note: Checked in the Search space paragraph on the page 8 image.
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Typo Page 8 reads "proposed in Zaremba et al. (2014) and (Gal, 2015)", mixing two citation styles; the second should be "Gal (2015)".
- p. 8 PTB dataset paragraph
Zaremba et al. (2014) and (Gal, 2015)
Judge's note: Checked in the PTB Dataset paragraph on the page 8 image. Cosmetic only.
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Typo Duplicated verb: "Not only is our cell is better, the model that achieves 64 perplexity..."
- p. 9 Section 4.2, Results
Not only is our cell is better
- p. 9
Not only is our cell is better, the model
Judge's note: Page 9 image, Results paragraph, shows the second "is" printed as quoted. It should read "Not only is our cell better".
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Typo Misspelling: "a distributed setting with a parameter sever and 12 workers" should read "parameter server".
- p. 10 GNMT paragraph
with a parameter sever and 12 workers
- p. 10 GNMT paragraph
a parameter sever and 12 workers
Judge's note: Page 10 image, GNMT paragraph, shows "parameter sever".
Second check: none (judge only)