benchmark: add naive string finding

FindStringNaive is a simple benchmark which implements a naive String
finding algorithm that currently shows a lot of ARC traffic, hopefully
to be reduced in the future.

Author: weissi

benchmark/CMakeLists.txt

@@ -87,6 +87,7 @@ set(SWIFT_BENCH_MODULES
     single-source/Exclusivity
     single-source/ExistentialPerformance
     single-source/Fibonacci
+    single-source/FindStringNaive
     single-source/FlattenList
     single-source/FloatingPointParsing
     single-source/FloatingPointPrinting

benchmark/single-source/FindStringNaive.swift

@@ -0,0 +1,185 @@
+//===--- FindStringNaive.swift --------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import TestsUtils
+
+// Mini benchmark implementing a naive String search algorithm that
+// at the moment shows a lot of ARC traffic.
+let t: [BenchmarkCategory] = [.String, .refcount]
+let N = 100
+
+var longStringFoFoFoFox: String?
+var longArrayFoFoFoFox: [UInt8]?
+
+public let FindStringNaive = [
+  BenchmarkInfo(
+    name: "FindString.Loop1.Substring",
+    runFunction: runBenchLoop1Substring,
+    tags: t,
+    setUpFunction: {
+      longStringFoFoFoFox = String(repeating: "fo", count: 5_000) + "fox <-- needle"
+    }),
+  BenchmarkInfo(
+    name: "FindString.Rec3.String",
+    runFunction: runBenchRecursive3String,
+    tags: t,
+    setUpFunction: {
+      longStringFoFoFoFox = String(repeating: "fo", count: 500) + "fox <-- needle"
+    }),
+  BenchmarkInfo(
+    name: "FindString.Rec3.Substring",
+    runFunction: runBenchRecursive3Substring,
+    tags: t,
+    setUpFunction: {
+      longStringFoFoFoFox = String(repeating: "fo", count: 500) + "fox <-- needle"
+    }),
+  BenchmarkInfo(
+    name: "FindString.Loop1.Array",
+    runFunction: runBenchLoop1Array,
+    tags: t,
+    setUpFunction: {
+      longArrayFoFoFoFox = []
+      longArrayFoFoFoFox!.reserveCapacity(1_100_000)
+      for _ in 0 ..< 500_000 {
+        longArrayFoFoFoFox!.append(contentsOf: "fo".utf8)
+      }
+      longArrayFoFoFoFox!.append(contentsOf: "fox <-- needle".utf8)
+    }),
+  BenchmarkInfo(
+    name: "FindString.Rec3.Array",
+    runFunction: runBenchRecursive3ArrayOfUTF8,
+    tags: t,
+    setUpFunction: {
+      longArrayFoFoFoFox = []
+      longArrayFoFoFoFox!.reserveCapacity(11_000)
+      for _ in 0 ..< 5_000 {
+        longArrayFoFoFoFox!.append(contentsOf: "fo".utf8)
+      }
+      longArrayFoFoFoFox!.append(contentsOf: "fox <-- needle".utf8)
+    }),
+]
+
+func findOne<S: StringProtocol>(
+  _ string: S,
+  needle: Character
+) -> String.Index? {
+  var index = string.startIndex
+  while index < string.endIndex {
+    let nextIndex = string.index(after: index)
+    if string[index] == needle {
+      return index
+    }
+    index = nextIndex
+  }
+  return nil
+}
+
+func findThreeRecursive<S: StringProtocol>(
+  _ string: S,
+  needle1: Character,
+  needle2: Character?,
+  needle3: Character?
+) -> String.Index? {
+  var index = string.startIndex
+  while index < string.endIndex {
+    let nextIndex = string.index(after: index)
+    if string[index] == needle1 {
+      // Check subsequent needles recursively (if applicable)
+      guard let needle2 = needle2 else { return index }
+
+      if findThreeRecursive(
+        string[nextIndex...].prefix(2), needle1: needle2, needle2: needle3, needle3: nil
+      ) == nextIndex {
+        return index
+      }
+    }
+    index = nextIndex
+  }
+  return nil
+}
+
+func findOneOnUTF8Collection<Bytes: Collection>(
+  _ string: Bytes,
+  needle: UInt8
+) -> Bytes.Index? where Bytes.Element == UInt8 {
+  var index = string.startIndex
+  while index < string.endIndex {
+    let nextIndex = string.index(after: index)
+    if string[index] == needle {
+      return index
+    }
+    index = nextIndex
+  }
+  return nil
+}
+
+func findThreeOnUTF8Collection<Bytes: Collection>(
+  _ string: Bytes,
+  needle1: UInt8,
+  needle2: UInt8?,
+  needle3: UInt8?
+) -> Bytes.Index? where Bytes.Element == UInt8 {
+  var index = string.startIndex
+  while index < string.endIndex {
+    let nextIndex = string.index(after: index)
+    if string[index] == needle1 {
+      // Check subsequent needles recursively (if applicable)
+      guard let needle2 = needle2 else { return index }
+
+      if findThreeOnUTF8Collection(
+        string[nextIndex...].prefix(2), needle1: needle2, needle2: needle3, needle3: nil
+      ) == nextIndex {
+        return index
+      }
+    }
+    index = nextIndex
+  }
+  return nil
+}
+
+@inline(never)
+func runBenchLoop1Substring(iterations: Int) {
+  for _ in 0 ..< iterations {
+    precondition(findOne(longStringFoFoFoFox![...], needle: "x") != nil)
+  }
+}
+
+@inline(never)
+func runBenchLoop1Array(iterations: Int) {
+  for _ in 0 ..< iterations {
+    precondition(findOneOnUTF8Collection(longArrayFoFoFoFox!, needle: UInt8(ascii: "x")) != nil)
+  }
+}
+
+@inline(never)
+func runBenchRecursive3Substring(iterations: Int) {
+  for _ in 0 ..< iterations {
+    precondition(findThreeRecursive(longStringFoFoFoFox![...], needle1: "f", needle2: "o", needle3: "x") != nil)
+  }
+}
+
+@inline(never)
+func runBenchRecursive3String(iterations: Int) {
+  for _ in 0 ..< iterations {
+    precondition(findThreeRecursive(longStringFoFoFoFox!, needle1: "f", needle2: "o", needle3: "x") != nil)
+  }
+}
+
+@inline(never)
+func runBenchRecursive3ArrayOfUTF8(iterations: Int) {
+  for _ in 0 ..< iterations {
+    precondition(findThreeOnUTF8Collection(longArrayFoFoFoFox!,
+                                      needle1: UInt8(ascii: "f"),
+                                      needle2: UInt8(ascii: "o"),
+                                      needle3: UInt8(ascii: "x")) != nil)
+  }
+}

benchmark/utils/main.swift

@@ -75,6 +75,7 @@ import ErrorHandling
 import Exclusivity
 import ExistentialPerformance
 import Fibonacci
+import FindStringNaive
 import FlattenList
 import FloatingPointParsing
 import FloatingPointPrinting
@@ -252,6 +253,7 @@ registerBenchmark(ErrorHandling)
 registerBenchmark(Exclusivity)
 registerBenchmark(ExistentialPerformance)
 registerBenchmark(Fibonacci)
+registerBenchmark(FindStringNaive)
 registerBenchmark(FlattenListLoop)
 registerBenchmark(FlattenListFlatMap)
 registerBenchmark(FloatingPointParsing)