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Lucian Ghinda
Lucian Ghinda

Posted on • Originally published at allaboutcoding.ghinda.com

Micro benchmarking value objects in Ruby: Data.define vs Struct vs OpenStruct

#ruby #performance #benchmark

As I was working on another email part of my Modern Ruby course via email I wanted to make some micro benchmarks on Data.define vs Struct vs OpenStruct

They are not a production-level benchmark, so take them with a grain of salt.

I added all code and results in a repo at https://github.com/lucianghinda/value-object-in-ruby-benchmarks

Creating new objects

When creating a new object, Struct (with keyword_init: true)and Data.define behave almost the same (the differences are with error margin or so small that they are probably due to my setup), while OpenStruct seems to be the slowest.

Having defines the following keys and values:

keys = 1000.times.map { |i| "key#{i}".to_sym }
values = 1000.times.map { |i| "value#{i}" }
keys_and_values = Hash[keys.zip(values)]
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The creation benchmarks are testing the following code:

DataStruct = Struct.new(*keys, keyword_init: true)
DataStruct.new(**keys_and_values)

# vs

DataDefine = Data.define(*keys)
DataDefine.new(**keys_and_values)

# vs

OpenStruct.new(**keys_and_values)
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Here is a `bmbm` benchmark result:

Creating a new object - Benchmark with bmbm
Rehearsal --------------------------------------------------
Struct.new       0.000023   0.000003   0.000026 (  0.000024)
Data.define      0.000020   0.000001   0.000021 (  0.000022)
OpenStruct.new   0.001705   0.000075   0.001780 (  0.001780)
----------------------------------------- total: 0.001827sec

                     user     system      total        real
Struct.new       0.000020   0.000000   0.000020 (  0.000020)
Data.define      0.000022   0.000000   0.000022 (  0.000022)
OpenStruct.new   0.001069   0.000044   0.001113 (  0.001132)
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Here is the ibs benchmark result:

Creating a new object - Benchmark with ips
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
Warming up --------------------------------------
          Struct.new     5.169k i/100ms
         Data.define     5.361k i/100ms
      OpenStruct.new    62.000 i/100ms
Calculating -------------------------------------
          Struct.new     50.086k (± 1.7%) i/s -    253.281k in   5.058450s
         Data.define     51.646k (± 1.1%) i/s -    262.689k in   5.086990s
      OpenStruct.new    607.447 (± 0.8%) i/s -      3.038k in   5.001584s

Comparison:
         Data.define:    51646.3 i/s
          Struct.new:    50085.7 i/s - 1.03x  slower
      OpenStruct.new:      607.4 i/s - 85.02x  slower
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Here is the memory benchmark result.

Creating a new object - Benchmark with ips
Calculating -------------------------------------
          Struct.new    36.792k memsize (     0.000  retained)
                         2.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
         Data.define    36.792k memsize (     0.000  retained)
                         2.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
      OpenStruct.new   848.728k memsize (     0.000  retained)
                         8.005k objects (     0.000  retained)
                        50.000  strings (     0.000  retained)

Comparison:
          Struct.new:      36792 allocated
         Data.define:      36792 allocated - same
      OpenStruct.new:     848728 allocated - 23.07x more
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Accessing attributes

Again Data.define and Struct with keyword arguments are the same. On the other side OpenStruct is almost twice as slow.

Having the following data defined:

keys = 1000.times.map { |i| "key#{i}".to_sym }
values = 1000.times.map { |i| "value#{i}" }
keys_and_values = Hash[keys.zip(values)]
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And then defining the following structures:

BigDataS = Struct.new(*keys, keyword_init: true)
BigDataD = Data.define(*keys)
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The benchmarks are comparing:

keys.each { struct_object.send(_1) }

keys.each { data_object.send(_1) }

keys.each { opens_struct_object.send(_1) }
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Here is the bmbm benchmark result:

Accessing attributes - bmbm test
Rehearsal -----------------------------------------------
Struct        0.000069   0.000002   0.000071 (  0.000071)
Data.define   0.000069   0.000003   0.000072 (  0.000071)
OpenStruct    0.000110   0.000003   0.000113 (  0.000116)
-------------------------------------- total: 0.000256sec

                  user     system      total        real
Struct        0.000049   0.000001   0.000050 (  0.000046)
Data.define   0.000046   0.000001   0.000047 (  0.000046)
OpenStruct    0.000091   0.000001   0.000092 (  0.000094)
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Here is the ibs benchmark result:

Accessing attributes - ips test
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
Warming up --------------------------------------
              Struct     2.857k i/100ms
         Data.define     2.828k i/100ms
          OpenStruct     1.384k i/100ms
Calculating -------------------------------------
              Struct     28.420k (± 0.9%) i/s -    142.850k in   5.026906s
         Data.define     28.691k (± 0.5%) i/s -    144.228k in   5.027131s
          OpenStruct     13.475k (± 0.9%) i/s -     67.816k in   5.033315s

Comparison:
         Data.define:    28690.8 i/s
              Struct:    28419.6 i/s - same-ish: difference falls within error
          OpenStruct:    13474.6 i/s - 2.13x  slower
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Context for understanding why Data.define and Struct are similar

Ufuk Kayserilioglu explains why Data.define and Struct with keyword arguments have the same behavior:

Ufuk explaining: "Data is (basically) just Struct with no writer methods defined (and a freeze, I believe). The CRuby codepaths are exactly the same for both, except zverok decided that Data#initialize should always accept kw arguments, so Data.new has to convert positional args to kw args before passing them to initialize."

A note about OpenStruct

Jean Boussier answered a question about why OpenStruct is so slow:

Jean Boussier explaining "It's not because it's written in Ruby but because of it's semantic. For every single instance it has to create a metaclass and define methods on it. It's terribly wasteful and doing the same in C wouldn't be much faster. OpenStruct should be considered deprecated really."

Updates

This article was updated on 2024-03-23 after Ufuk Kayserilioglu added a PR to the repo after he noticed an error in my benchmarking where I was comparing Data.define with Struct with positional arguments. And I also added an explanation shared by Jean Boussier about the slowness of OpenStruct and an explanation by Ufuk about the similar behavior of Data.define and Struct.

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