1 files changed, 94 insertions, 0 deletions
diff --git a/third_party/highway/hwy/nanobenchmark_test.cc b/third_party/highway/hwy/nanobenchmark_test.cc
new file mode 100644
index 0000000000..0d153a14c5
--- /dev/null
+++ b/third_party/highway/hwy/nanobenchmark_test.cc
@@ -0,0 +1,94 @@
+// Copyright 2019 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "hwy/nanobenchmark.h"
+
+#ifndef __STDC_FORMAT_MACROS
+#define __STDC_FORMAT_MACROS  // before inttypes.h
+#endif
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include <random>
+
+#include "hwy/tests/test_util-inl.h"
+
+namespace hwy {
+namespace {
+
+// Governs duration of test; avoid timeout in debug builds.
+#if HWY_IS_DEBUG_BUILD
+constexpr size_t kMaxEvals = 3;
+#else
+constexpr size_t kMaxEvals = 4;
+#endif
+
+FuncOutput Div(const void*, FuncInput in) {
+  // Here we're measuring the throughput because benchmark invocations are
+  // independent. Any dividend will do; the divisor is nonzero.
+  return 0xFFFFF / in;
+}
+
+template <size_t N>
+void MeasureDiv(const FuncInput (&inputs)[N]) {
+  printf("Measuring integer division (output on final two lines)\n");
+  Result results[N];
+  Params params;
+  params.max_evals = kMaxEvals;
+  const size_t num_results = Measure(&Div, nullptr, inputs, N, results, params);
+  for (size_t i = 0; i < num_results; ++i) {
+    printf("%5" PRIu64 ": %6.2f ticks; MAD=%4.2f%%\n",
+           static_cast<uint64_t>(results[i].input), results[i].ticks,
+           results[i].variability * 100.0);
+  }
+}
+
+std::mt19937 rng;
+
+// A function whose runtime depends on rng.
+FuncOutput Random(const void* /*arg*/, FuncInput in) {
+  const size_t r = rng() & 0xF;
+  FuncOutput ret = static_cast<FuncOutput>(in);
+  for (size_t i = 0; i < r; ++i) {
+    ret /= ((rng() & 1) + 2);
+  }
+  return ret;
+}
+
+// Ensure the measured variability is high.
+template <size_t N>
+void MeasureRandom(const FuncInput (&inputs)[N]) {
+  Result results[N];
+  Params p;
+  p.max_evals = kMaxEvals;
+  p.verbose = false;
+  const size_t num_results = Measure(&Random, nullptr, inputs, N, results, p);
+  for (size_t i = 0; i < num_results; ++i) {
+    NANOBENCHMARK_CHECK(results[i].variability > 1E-3);
+  }
+}
+
+TEST(NanobenchmarkTest, RunAll) {
+  const int unpredictable = Unpredictable1();  // == 1, unknown to compiler.
+  static const FuncInput inputs[] = {static_cast<FuncInput>(unpredictable) + 2,
+                                     static_cast<FuncInput>(unpredictable + 9)};
+
+  MeasureDiv(inputs);
+  MeasureRandom(inputs);
+}
+
+}  // namespace
+}  // namespace hwy