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https://github.com/simdjson/simdjson
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John Keiser
50 lines
2.1 KiB
Markdown
50 lines
2.1 KiB
Markdown
# Top Tweet Benchmark
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The top_tweet benchmark finds the most-retweeted tweet in a twitter API response.
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## Purpose
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This scenario tends to measure an implementation's laziness: its ability to avoid parsing unneeded
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values, without knowing beforehand which values are needed.
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To find the top tweet, an implementation needs to iterate through all tweets, remembering which one
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had the highest retweet count. While it scans, it will find many "candidate" tweets with the highest
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retweet count *up to that point.* However, While the implementation iterates through tweets, it will
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have many "candidate" tweets. Essentially, it has to keep track of the "top tweet so far" while it
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searches. However, only the text and screen_name of the *final* top tweet need to be parsed.
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Therefore, JSON parsers that can only parse values on the first pass (such as DOM or streaming
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parsers) will be forced to parse text and screen_name of every candidate (if not every single
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tweet). Parsers which can delay parsing of values until later will therefore shine in scenarios like
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this.
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## Rules
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The benchmark will be called with `run(padded_string &json, int64_t max_retweet_count, top_tweet_result &result)`.
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The benchmark must:
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- Find the tweet with the highest retweet_count at the top level of the "statuses" array.
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- Find the *last* such tweet: if multiple tweets have the same top retweet_count, the last one
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should be returned.
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- Exclude tweets with retweet_count above max_retweet_count. This restriction is solely here because
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the default twitter.json has a rather high retweet count in the third tweet, and to test laziness
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the matching tweet needs to be further down in the file.
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- Fill in top_tweet_result with the corresponding fields from the matching tweet.
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### Abridged Schema
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The abridged schema (objects contain more fields than listed here):
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```json
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{
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"statuses": [
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{
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"text": "i like to tweet", // text containing UTF-8 and escape characters
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"user": {
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"screen_name": "AlexanderHamilton" // string containing UTF-8 (and escape characters?)
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},
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"retweet_count": 2, // uint32
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},
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...
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]
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}
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```
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