First benchmark: Looking at Xgit.Repository.WorkingTree.ParseIndexFil…

…e.from_iodevice/1. (#167)

.formatter.exs

@@ -1,4 +1,4 @@
 [
-  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"],
+  inputs: ["{mix,.formatter}.exs", "{bench,config,lib,test}/**/*.{ex,exs}"],
   locals_without_parens: [cover: 1]
 ]

bench/README.md

@@ -0,0 +1,31 @@
+When there's a concern about algorithmic or absolute cost of a specific implementation,
+let's build a microbenchmark here. As of this writing (mid-September 2019), I think the
+following functions need study.
+
+```
+Xgit.Core.DirCache
+	add_entries/2
+	fully_merged?/1
+	remove_entries/2
+	to_tree_objects/2
+
+Xgit.Core.FilePath
+	check_path_segment/2
+	check_path/2
+	valid?/2
+
+Xgit.Core.Object
+	valid?/1
+
+Xgit.Core.Tree
+	from_object/1
+	to_object/1
+
+Xgit.Repository (permute on the implementations)
+	get_object/2
+	has_all_object_ids?/2
+	put_loose_object/2
+
+Xgit.Repository.WorkingTree.WriteIndexFile
+	to_iodevice/1
+```

bench/xgit/repository/working_tree/parse_index_file/from_iodevice.exs

@@ -0,0 +1,92 @@
+# Measure cost of Xgit.Repository.WorkingTree.ParseIndexFile.from_iodevice/1.
+#
+# EXPECTED: Cost is roughly O(n) on the number of items in the index file.
+#
+# --------------------------------------------------------------------------------------
+#
+# $ mix run bench/xgit/repository/working_tree/parse_index_file/from_iodevice.exs
+# Operating System: macOS
+# CPU Information: Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
+# Number of Available Cores: 8
+# Available memory: 16 GB
+# Elixir 1.9.1
+# Erlang 22.0.7
+#
+# Benchmark suite executing with the following configuration:
+# warmup: 2 s
+# time: 5 s
+# memory time: 0 ns
+# parallel: 1
+# inputs: 10 items, 100 items, 1000 items
+# Estimated total run time: 21 s
+#
+# Benchmarking parse_index_file with input 10 items...
+# Benchmarking parse_index_file with input 100 items...
+# Benchmarking parse_index_file with input 1000 items...
+#
+# ##### With input 10 items #####
+# Name                       ips        average  deviation         median         99th %
+# parse_index_file        1.14 K      880.11 μs     ±7.61%         871 μs     1090.70 μs
+#
+# ##### With input 100 items #####
+# Name                       ips        average  deviation         median         99th %
+# parse_index_file        146.25        6.84 ms     ±3.99%        6.81 ms        7.69 ms
+#
+# ##### With input 1000 items #####
+# Name                       ips        average  deviation         median         99th %
+# parse_index_file         14.87       67.23 ms     ±1.97%       67.01 ms       73.24 ms
+#
+# --------------------------------------------------------------------------------------
+
+alias Xgit.Repository.WorkingTree.ParseIndexFile
+alias Xgit.Util.TrailingHashDevice
+
+Temp.track!()
+
+make_index_file_with_n_entries = fn n ->
+  git_dir = Temp.mkdir!()
+
+  {_output, 0} = System.cmd("git", ["init"], cd: git_dir)
+
+  Enum.map(1..n, fn i ->
+    name = "0000#{i}"
+
+    {_output, _0} =
+      System.cmd(
+        "git",
+        [
+          "update-index",
+          "--add",
+          "--cacheinfo",
+          "100644",
+          "18832d35117ef2f013c4009f5b2128dfaeff354f",
+          "a#{String.slice(name, -4, 4)}"
+        ],
+        cd: git_dir
+      )
+  end)
+
+  Path.join([git_dir, ".git", "index"])
+end
+
+thd_open_file! = fn path ->
+  {:ok, iodevice} = TrailingHashDevice.open_file(path)
+  iodevice
+end
+
+inputs = %{
+  "10 items" => make_index_file_with_n_entries.(10),
+  "100 items" => make_index_file_with_n_entries.(100),
+  "1000 items" => make_index_file_with_n_entries.(1000)
+}
+
+Benchee.run(
+  %{
+    "parse_index_file" => fn index_file_path ->
+      iodevice = thd_open_file!.(index_file_path)
+      ParseIndexFile.from_iodevice(iodevice)
+      File.close(iodevice)
+    end
+  },
+  inputs: inputs
+)

mix.exs

@@ -25,12 +25,13 @@ defmodule Xgit.MixProject do
 
   defp deps do
     [
+      {:benchee, "~> 1.0", only: :dev},
       {:con_cache, "~> 0.13"},
       {:credo, "~> 1.1", only: [:dev, :test]},
       {:dialyxir, "~> 1.0.0-rc.6", only: :dev, runtime: false},
       {:excoveralls, "~> 0.11", only: :test},
       {:ex_doc, "~> 0.21", only: :dev},
-      {:temp, "~> 0.4", only: :test}
+      {:temp, "~> 0.4", only: [:dev, :test]}
     ]
   end
 

mix.lock

@@ -1,12 +1,14 @@
 %{
+  "benchee": {:hex, :benchee, "1.0.1", "66b211f9bfd84bd97e6d1beaddf8fc2312aaabe192f776e8931cb0c16f53a521", [:mix], [{:deep_merge, "~> 1.0", [hex: :deep_merge, optional: false]}]},
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], []},
   "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, optional: false]}]},
   "con_cache": {:hex, :con_cache, "0.14.0", "863acb90fa08017be3129074993af944cf7a4b6c3ee7c06c5cd0ed6b94fbc223", [:mix], []},
-  "credo": {:hex, :credo, "1.1.4", "c2f3b73c895d81d859cec7fcee7ffdb972c595fd8e85ab6f8c2adbf01cf7c29c", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
+  "credo": {:hex, :credo, "1.1.4", "c2f3b73c895d81d859cec7fcee7ffdb972c595fd8e85ab6f8c2adbf01cf7c29c", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, optional: false]}, {:jason, "~> 1.0", [hex: :jason, optional: false]}]},
+  "deep_merge": {:hex, :deep_merge, "1.0.0", "b4aa1a0d1acac393bdf38b2291af38cb1d4a52806cf7a4906f718e1feb5ee961", [:mix], []},
   "dialyxir": {:hex, :dialyxir, "1.0.0-rc.6", "78e97d9c0ff1b5521dd68041193891aebebce52fc3b93463c0a6806874557d7d", [:mix], [{:erlex, "~> 0.2.1", [hex: :erlex, optional: false]}]},
-  "earmark": {:hex, :earmark, "1.3.6", "ce1d0675e10a5bb46b007549362bd3f5f08908843957687d8484fe7f37466b19", [:mix], [], "hexpm"},
+  "earmark": {:hex, :earmark, "1.3.6", "ce1d0675e10a5bb46b007549362bd3f5f08908843957687d8484fe7f37466b19", [:mix], []},
   "erlex": {:hex, :erlex, "0.2.4", "23791959df45fe8f01f388c6f7eb733cc361668cbeedd801bf491c55a029917b", [:mix], []},
-  "ex_doc": {:hex, :ex_doc, "0.21.2", "caca5bc28ed7b3bdc0b662f8afe2bee1eedb5c3cf7b322feeeb7c6ebbde089d6", [:mix], [{:earmark, "~> 1.3.3 or ~> 1.4", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
+  "ex_doc": {:hex, :ex_doc, "0.21.2", "caca5bc28ed7b3bdc0b662f8afe2bee1eedb5c3cf7b322feeeb7c6ebbde089d6", [:mix], [{:earmark, "~> 1.3.3 or ~> 1.4", [hex: :earmark, optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, optional: false]}]},
   "excoveralls": {:hex, :excoveralls, "0.11.2", "0c6f2c8db7683b0caa9d490fb8125709c54580b4255ffa7ad35f3264b075a643", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, optional: false]}, {:jason, "~> 1.0", [hex: :jason, optional: false]}]},
   "hackney": {:hex, :hackney, "1.15.1", "9f8f471c844b8ce395f7b6d8398139e26ddca9ebc171a8b91342ee15a19963f4", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, optional: false]}, {:idna, "6.0.0", [hex: :idna, optional: false]}, {:metrics, "1.0.1", [hex: :metrics, optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, optional: false]}]},
   "idna": {:hex, :idna, "6.0.0", "689c46cbcdf3524c44d5f3dde8001f364cd7608a99556d8fbd8239a5798d4c10", [:rebar3], [{:unicode_util_compat, "0.4.1", [hex: :unicode_util_compat, optional: false]}]},