stub in sub-project benchmark with a single benchmark

Author: heckj

ExternalBenchmarks/.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj
+xcuserdata/
+DerivedData/
+.swiftpm/config/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc
+.vscode

ExternalBenchmarks/Benchmarks/ExternalBenchmarks/ExternalBenchmarks.swift

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+import Benchmark
+import Noise
+import Foundation
+
+let viewer_size: Int = 1024
+let offset: Double = 0
+
+// running at roughly 500ms for a pass, so maxDuration will limit far before iteration count for this
+func cell2d() async -> Data {
+    var pixbuf:[UInt8]  = [UInt8](repeating: 0, count: viewer_size * viewer_size)
+    for (i, (x, y)) in Domain2D(samples_x: viewer_size, samples_y: viewer_size).enumerated() {
+        pixbuf[i] = UInt8(max(0, min(255, CellNoise2D(amplitude: 255, frequency: 0.01).evaluate(x, y) + offset)))
+    }
+    return Data(pixbuf)
+}
+
+let benchmarks = {
+    Benchmark.defaultConfiguration.maxIterations = .count(100_000) // same as default
+    Benchmark.defaultConfiguration.maxDuration = .seconds(5)
+    Benchmark.defaultConfiguration.metrics = [.throughput, .wallClock]
+    
+    Benchmark("cell2d") { benchmark in
+        for _ in benchmark.scaledIterations {
+            blackHole(await cell2d())
+        }
+    }
+}
+

ExternalBenchmarks/Package.resolved

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+// swift-tools-version: 5.9
+
+import PackageDescription
+
+let package = Package(
+    name: "ExternalBenchmarks",
+    platforms: [
+        .macOS(.v13),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/ordo-one/package-benchmark", .upToNextMajor(from: "1.0.0")),
+        .package(path: "../"),
+    ],
+    targets: [
+        .executableTarget(
+            name: "ExternalBenchmarks",
+            dependencies: [
+                .product(name: "Benchmark", package: "package-benchmark"),
+                .product(name: "BenchmarkPlugin", package: "package-benchmark"),
+                .product(name: "Noise", package: "swift-noise"),
+            ],
+            path: "Benchmarks/ExternalBenchmarks"
+        )
+    ]
+)

ExternalBenchmarks/Package.swift

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+# ExternalBenchmarks
+
+Additional benchmarks that utilize https://github.com/ordo-one/package-benchmark.
+
+This code is explicitly in a subdirectory with a local reference to swift-noise
+in order avoid adding transitive dependencies.
+
+To run the benchmarks, invoke the following command:
+
+    swift package benchmark