Move benchmark buck file into benchmark directory

Summary: buck rules are not meant to be in the root buck file but instead next to source files. This diff moves benchmark rule into benchmark folder.

Reviewed By: lucasr

Differential Revision: D3992992

fbshipit-source-id: 34782ff73bbd5b799d83d0f01b553bfab928f1df

benchmark/CSSBenchmark.h

@@ -0,0 +1,73 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#pragma once
+
+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define NUM_REPETITIONS 100
+
+#define CSS_BENCHMARKS(BLOCK)              \
+  int main(int argc, char const *argv[]) { \
+    clock_t __start;                       \
+    clock_t __endTimes[NUM_REPETITIONS];   \
+    { BLOCK }                              \
+    return 0;                              \
+  }
+
+#define CSS_BENCHMARK(NAME, BLOCK)                       \
+  __start = clock();                                     \
+  for (uint32_t __i = 0; __i < NUM_REPETITIONS; __i++) { \
+    { BLOCK }                                            \
+    __endTimes[__i] = clock();                           \
+  }                                                      \
+  __printBenchmarkResult(NAME, __start, __endTimes);
+
+int __compareDoubles(const void *a, const void *b) {
+  double arg1 = *(const double *) a;
+  double arg2 = *(const double *) b;
+
+  if (arg1 < arg2) {
+    return -1;
+  }
+
+  if (arg1 > arg2) {
+    return 1;
+  }
+
+  return 0;
+}
+
+void __printBenchmarkResult(char *name, clock_t start, clock_t *endTimes) {
+  double timesInMs[NUM_REPETITIONS];
+  double mean = 0;
+  clock_t lastEnd = start;
+  for (uint32_t i = 0; i < NUM_REPETITIONS; i++) {
+    timesInMs[i] = (endTimes[i] - lastEnd) / (double) CLOCKS_PER_SEC * 1000;
+    lastEnd = endTimes[i];
+    mean += timesInMs[i];
+  }
+  mean /= NUM_REPETITIONS;
+
+  qsort(timesInMs, NUM_REPETITIONS, sizeof(double), __compareDoubles);
+  double median = timesInMs[NUM_REPETITIONS / 2];
+
+  double variance = 0;
+  for (uint32_t i = 0; i < NUM_REPETITIONS; i++) {
+    variance += pow(timesInMs[i] - mean, 2);
+  }
+  variance /= NUM_REPETITIONS;
+  double stddev = sqrt(variance);
+
+  printf("%s: median: %lf ms, stddev: %lf ms\n", name, median, stddev);
+}