Merge pull request #13731 from lorentey/romannumbers

[benchmark] Add roman numeral conversion benchmark

Author: lorentey

benchmark/CMakeLists.txt

@@ -119,6 +119,7 @@ set(SWIFT_BENCH_MODULES
     single-source/RecursiveOwnedParameter
     single-source/ReduceInto
     single-source/ReversedCollections
+    single-source/RomanNumbers
     single-source/SetTests
     single-source/SevenBoom
     single-source/Sim2DArray

benchmark/single-source/RomanNumbers.swift

@@ -0,0 +1,95 @@
+//===--- RomanNumbers.swift -----------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2018 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 roman numeral conversions to/from integers.
+// Measures performance of Substring.starts(with:) and String.append(),
+// with very short string arguments.
+//
+
+public let RomanNumbers = [
+  BenchmarkInfo(
+    name: "RomanNumbers",
+    runFunction: run_RomanNumbers,
+    tags: [.api, .String, .algorithm])
+]
+
+let romanTable: DictionaryLiteral<String, Int> = [
+  "M": 1000,
+  "CM": 900,
+  "D": 500,
+  "CD": 400,
+  "C": 100,
+  "XC": 90,
+  "L": 50,
+  "XL": 40,
+  "X": 10,
+  "IX": 9,
+  "V": 5,
+  "IV": 4,
+  "I": 1,
+]
+
+extension BinaryInteger {
+  var romanNumeral: String {
+    var result = ""
+    var value = self
+  outer:
+    while value > 0 {
+      var position = 0
+      for (i, (key: s, value: v)) in romanTable[position...].enumerated() {
+        if value >= v {
+          result += s
+          value -= Self(v)
+          position = i
+          continue outer
+        }
+      }
+      fatalError("Unreachable")
+    }
+    return result
+  }
+
+  init?(romanNumeral: String) {
+    self = 0
+    var input = Substring(romanNumeral)
+  outer:
+    while !input.isEmpty {
+      var position = 0
+      for (i, (key: s, value: v)) in romanTable[position...].enumerated() {
+        if input.starts(with: s) {
+          self += Self(v)
+          input = input.dropFirst(s.count)
+          position = i
+          continue outer
+        }
+      }
+      return nil
+    }
+  }
+}
+
+@inline(never)
+func checkRomanNumerals(upTo limit: Int) {
+  for i in 0 ..< limit {
+    CheckResults(Int(romanNumeral: identity(i.romanNumeral)) == i)
+  }
+}
+
+@inline(never)
+public func run_RomanNumbers(_ N: Int) {
+  for _ in 0 ..< 10 * N {
+    checkRomanNumerals(upTo: 1100)
+  }
+}

benchmark/utils/main.swift

@@ -107,6 +107,7 @@ import RangeReplaceableCollectionPlusDefault
 import RecursiveOwnedParameter
 import ReduceInto
 import ReversedCollections
+import RomanNumbers
 import SetTests
 import SevenBoom
 import Sim2DArray
@@ -242,6 +243,7 @@ registerBenchmark(RangeReplaceableCollectionPlusDefault)
 registerBenchmark(RecursiveOwnedParameter)
 registerBenchmark(ReduceInto)
 registerBenchmark(ReversedCollections)
+registerBenchmark(RomanNumbers)
 registerBenchmark(SetTests)
 registerBenchmark(SevenBoom)
 registerBenchmark(Sim2DArray)