- that's what the experts say. And what is left for the naughty ones who want to efficiently search through a huge number of templates? "Don't use regular expressions, otherwise you'll have 2 problems instead of 1" Sure, there are cool solutions like or for this specific problem. However, for my project it seemed impractical to master these fine technologies for the time being. Ragel re2c In this article, we will look at alternatives to the standard regexp library in Go and benchmark them for speed and memory consumption. We will also consider the differences between them from a practical point of view. Analogues At the moment, I've found the following working alternatives to the default that can be used to find patterns in Go (the versions used in the benchmarks are given in brackets): regexp (1.3.0) - as simple as possible replaces the default regexp. Uses to improve performance when dealing with large inputs or complex expressions; go-re2 C++ re2 (1.10.0) - a feature-rich regexp engine for . It does not have runtime guarantees like the built-in regexp package, but is compatible with Perl5 and .NET; regexp2 Go (1.0.0) - provides support for compatible regular expressions using or . JIT compilation is available, making this fork much faster than its counterparts. On the downside, you'll need the dependency; go-pcre Perl libpcre libpcre++ libpcre3-dev (regex 1.9.3) - uses the regex engine with bindings. The downside is a library dependency that needs to be compiled; rure-go Rust CGo Rust (1.2.2 + hs5.4.1) - regex engine designed for high performance. It is implemented as a library that provides a simple . It also requires compilation and linking of third-party dependencies; gohs C-API - A tool for identifying and classifying malware samples. Although has functionality for templating and regular expressions, it is very limited, so I will not include this library in the upcoming tests. go-yara YARA Existing benchmarks Before we start comparing the aforementioned solutions, it is worth to show how bad things are with the standard regex library in . I found the where the author compares the performance of standard regex engines of various languages. The point of this benchmark is to repeatedly run 3 regular expressions over a predefined text. came in in this benchmark! Go project Go 3rd place From the end... Language Email(ms) URI(ms) IP(ms) Total(ms) Nim Regex 1.32 26.92 7.84 36.09 Nim 22.70 21.49 6.75 50.94 Rust 26.66 25.70 5.28 57.63 ... ... ... ... ... Python PyPy3 258.78 221.89 257.35 738.03 Python 3 273.86 190.79 319.13 783.78 Go 248.14 241.28 360.90 850.32 C++ STL 433.09 344.74 245.66 1023.49 C# Mono 2859.05 2431.87 145.82 5436.75 . From other benchmarks I can highlight the following: As far as I can tell, benchmarking regex engines is not the easiest topic, because you need to know implementation and algorithm details for a correct comparison - comparison of engines with optimized versions for each language. For example, is no longer at the bottom, but it is still far from ideal there... And of course it does not use a native library, but a wrapper over PCRE - , which was specified in analogues. Benchmarks Game Go go-pcre - Comparison of different regex engines (PCRE, PCRE-DFA, TRE, Oniguruma, RE2, PCRE-JIT). Performance comparison of regular expression engines - here the author tries to compare engines using different regular expressions, which can complicate things depending on the engine implementation. In this benchmark, the author's top three engines are: Hyperscan, PCRE (with JIT compilation) and Rust regex ( uses it): A comparison of regex engines rure Benchmark #1 Now let's try to compare the analogues with default regex engine libraries of other languages. And also see how much faster they are compared to the default . To do this, I updated the above project by adding new libraries code. Here is what I got after running it on my machine: Go regex Language Email(ms) URI(ms) IP(ms) Total(ms) Go Rure 2.61 2.11 3.33 8.05 C++ SRELL 1.74 3.03 10.67 15.45 Rust 11.66 1.70 5.13 18.48 Nim 13.98 14.35 3.13 31.46 PHP 14.43 14.63 4.87 33.93 Go PCRE 14.18 14.98 6.21 35.37 C# .Net Core 10.83 5.10 26.71 42.64 Javascript 42.78 30.17 0.92 73.87 Go Re2 35.81 37.86 33.79 107.46 Go Hyperscan 90.17 31.64 8.68 130.49 Perl 92.51 66.42 22.51 181.44 Dart 73.48 63.60 80.52 217.59 C PCRE2 110.87 100.57 10.50 221.94 Kotlin 120.31 163.53 293.69 577.53 Java 205.14 201.55 295.68 702.36 Python 3 246.26 176.01 303.08 725.34 C++ STL 328.87 273.43 230.35 832.64 Go 270.19 275.73 504.79 1050.71 Go Regexp2 1703.51 1482.60 64.46 3250.57 C# Mono 2543.82 2139.44 110.37 4793.64 . Ps. Shortened the table a bit, so please check the to see all the results. project fork Pss. In this case, virtualization might have affected the results (the tests were performed in a Docker environment on Windows 11). Still, you can see how much faster regexps can be with some libraries! We even outperformed Rust with a Go library that uses the Rust library 🥴🙆🏼‍♂️. Perhaps this is what the author of this solution is trying to explain to us in his . repository As a result, almost all alternative solutions give us a speedup of times! Except for , which turns out to be slower than the standard library. 8-130 Regexp2 Benchmark #2 Questions While studying the existing benchmarks and the results of , I was lacking the answers to the following questions: Benchmark#1 How fast do the above libraries process large files? How much faster is the processing when grouping regular expressions? How fast will regular expressions with no matches in the text be processed? How much memory do the different libraries use? How many regexps will I be able to compile using grouping? Benchmarker differences To answer these questions, I wrote a small benchmarking program that can be used to compare different regex engines in terms of speed and memory usage. If you want to test it yourself or evaluate the correctness of the used methods, here is the . code The following features of this benchmark are worth mentioning: In the tests below, I used different regular expressions: 5 allRegexps["email"] = `(?P<name>[-\w\d\.]+?)(?:\s+at\s+|\s*@\s*|\s*(?:[\[\]@]){3}\s*)(?P<host>[-\w\d\.]*?)\s*(?:dot|\.|(?:[\[\]dot\.]){3,5})\s*(?P<domain>\w+)`
allRegexps["bitcoin"] = `\b([13][a-km-zA-HJ-NP-Z1-9]{25,34}|bc1[ac-hj-np-zAC-HJ-NP-Z02-9]{11,71})`
allRegexps["ssn"] = `\d{3}-\d{2}-\d{4}`
allRegexps["uri"] = `[\w]+://[^/\s?#]+[^\s?#]+(?:\?[^\s#]*)?(?:#[^\s]*)?`
allRegexps["tel"] = `\+\d{1,4}?[-.\s]?\(?\d{1,3}?\)?[-.\s]?\d{1,4}[-.\s]?\d{1,4}[-.\s]?\d{1,9}` In a good way, I should have used tricky regular expressions, like other benchmark authors do - to check the "weaknesses" of the algorithms. But I don't have much insight into the under-the-hood details of engines, so I used general-purpose regexps. That's why I think it should be possible to evaluate different parameters of libraries from a practical point of view. Instead of a static file, we will use a string containing our matches, repeated many times in memory to simulate files of different sizes: var data = bytes.Repeat([]byte("123@mail.co nümbr=+71112223334 SSN:123-45-6789 http://1.1.1.1 3FZbgi29cpjq2GjdwV8eyHuJJnkLtktZc5 Й"), config.repeatScanTimes) In addition to running the regexps sequentially over the data, there will be a separate run with named grouping of regular expressions, where they will take the following form: `(?P<name_1>regexp_1)|(?P<name_2>regexp_2)|...|(?P<name_N>regexp_N)` By the way, Hyperscan has a special functionality where we can build a database of regexps and use it against data. In the benchmarks I will use this method. Unlike in , for each regexp I will measure the time to find the result, without taking into account the compilation time; Benchmark#1 In the end, we will get the results for each library and each regexp in the following form: Generate data...
Test data size: 100.00MB

Run RURE:
  [bitcoin] count=1000000, mem=16007.26KB, time=2.11075s 
  [ssn] count=1000000, mem=16007.26KB, time=62.074ms 
  [uri] count=1000000, mem=16007.26KB, time=69.186ms 
  [tel] count=1000000, mem=16007.26KB, time=83.101ms 
  [email] count=1000000, mem=16007.26KB, time=172.915ms 
Total. Counted: 5000000, Memory: 80.04MB, Duration: 2.498027s
... 1-2. Processing large files and grouping regular expressions By "large file" I mean the amount of data generated from our predefined string in memory equal to . Of course it's hardly a big file, but I didn't want to wait hours for results in some cases 😅. 100MB Also, it makes sense to try grouping all regular expressions into one and see how much it affects performance. The hypothesis is that a sequential run of regexps over the data should take longer than a single run with a grouped regexp. Well, let's run the benchmark and see how fast each library processes the data. You can do this with my tool as follows: # Bench all libs, repeat the line 1000000 times (100MB)
regexcmp 1000000 
# Bench individual lib
regexcmp 1000000 rure
# See all options
regexcmp -h As a result, we have the following data: Lib Email Tel URI SSN Bitcoin Total Total-group Rure 0.173s 0.083s 0.069s 0.062s 2.11s 2.49s 10.13s PCRE 49.5s 0.367s 2.92s 2.07s 2.19s 57.07s 9.94s Re2 0.954s 0.63s 0.956s 0.945s 1.05s 4.54s 3.24s Hyperscan 0.469s 1.09s 0.669s 0.174s 1.97s 4.38s 4.97s Regexp2 126.4s 1.02s 21.51s 2.63s 3.38s 154.9s 20.65s Go regexp 11.22s 1.52s 3.62s 2.66s 3.32s 22.36s 26.49s The plot below shows the processing time of 100MB of data by all regexps in sequential mode and using grouping: : Conclusions Grouping can indeed significantly improve execution speed, but in some cases it can make it worse :); The fastest in sequential processing turned out to be - , with grouping - ; Rure Re2 Certain regexps may cause problems with some libraries (time to find in and ); email Regexp2 PCRE Now it is hard to say that some solutions are 180 times faster than the standard library, the maximum gain is . x8-9 3. Non-matching regexps In the previous case, we simulated the ideal situation where there are always matches in the data. But what if there are no hits for regexp in the text, how much will that affect performance? In this test, I additionally added modified regexps for SSN that do not match the data. In this case, means regexp, and - . Not a big difference? But let's see how it affects the time it takes to find all the matches: 5 SSN \d{3}-\d{2}-\d{4} Non-matching \d{3}-\d{2}-\d{4}1 Lib SSN Non-matching Total Total-group Rure 0.06s 0.083s 2.93s 15.68s PCRE 2.06s 4.21s 81.02s 13.52s Re2 0.960s 0.449s 6.75s 3.26s Hyperscan 0.175s 0.043s 4.61s 4.94s Regexp2 2.73s 3.09s 171.1s 15.72s Go regexp 2.66s 2.57s 35.13s 37.66s The plot below shows the time taken to process all regexps, sorted by processing time: 10 Non-matching : Conclusions This time is the same: the fastest in sequential processing was - , with grouped expressions - ; Rure Re2 is once again different, with time to process regexps in sequential mode; PCRE 2x non-matching Some algorithms are much faster when there are no matches ( , ); Re2 Hyperscan 4. Memory consumption Now let's see how much memory the different solutions consume when processing a 100MB file. Below, I have provided the results for each individual regexp and the total amount of memory consumed: Lib Email, MB Tel, MB URI, MB SSN, MB Bitcoin, MB Non-matching, KB Total, GB Total-group, GB Rure 16 16 16 16 16 0.0001 0.08 0.08 PCRE 186 186 186 186 186 0.38 0.93 0.9 Re2 254 254 254 255 254 100473 1.77 0.97 Hyperscan 314 314 314 314 314 0.68 1.57 1.7 Regexp2 997 854 854 854 902 396006 6.44 5.23 Go regex 191 144 144 160 208 3.62 0.78 1.8 The graph below shows the memory used by the libraries to process regexps (as in the last test), sorted by the time of `non-mathcing': 10 Conclusions: surprises with its practically zero memory consumption; Rure is resource hungry, consuming significantly more memory than its competitors; Regexp2 , despite its speed, is not the most memory-efficient solution; Re2 is on the good side, with relatively low costs in sequential mode. Go regex 5. Maximum number of regexps The main questions seem to be answered. Now let's see the maximum number of regexps we can compile with different solutions. In this case we will take a single regexp and repeat it many times in groups. For this purpose I will use the regexp: URI `[\w]+://[^/\s?#]+[^\s?#]+(?:\?[^\s#]*)?(?:#[^\s]*)?` Next, I've listed the results of compiling the regexps, along with the memory they use. The numbers in the first line are the number of expressions in the group: URI Lib 100 250 500 1000 5000 10000 Rure 0.38MB ❌ ❌ ❌ ❌ ❌ PCRE 0.40MB 2.37MB ❌ ❌ ❌ ❌ Re2 7.10MB 15.51MB 38.35MB 92.79MB 1181MB ❌ Hyperscan 0.03MB 0.06MB 0.12MB 0.25MB 1.21MB 2.52MB Regexp2 1.06MB 3.96MB 12.56MB 43.93MB 926MB 3604MB Go regex 1.29MB 4.52MB 14.02MB 47.18MB 942MB 3636MB : Conclusions As we can see, some solutions have limitations on the size of compiled regexps; not only allows to use a large number of regexps, but also uses minimal memory for compiled regexps; Hyperscan and have comparable memory consumption and also allow to compile a large number of regexps; Regexp2 Go Regex consumes the most memory at compile time. Re2 Conclusion I hope it was useful for you to learn about alternative solutions for regexps in , and based on the data I presented, everyone will be able to draw some conclusions for themselves, which will allow you to choose the most suitable regex solution for your situation. Go We can compare these libraries, the algorithms they use, their best/worst sides in details and for a long time. I just wanted to show the difference between them in the most general cases. Thus, I would advise you to look at for maximum speedup of regexps, but if you need the easiest library installation without dependencies, that is . And in the case of handling a large number of regexps would be a good choice. Also, don't forget the cost of using in some libraries. rure-go go-re2 hyperscan CGo As for me, I will definitely use these "findings" in my future :). project

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Best Regexp Alternative for Go; Benchmarks and Plots

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