bench.cpp

#include <cstddef>
#define max(a, b) (((a) < (b)) ? (b) : (a))

int test(int const *const nums, size_t const size, int const bound1, int const bound2, int const bound3) {
  int counter1 = 0;
  int counter2 = 0;
  int counter3 = 0;
  int counter4 = 0;
  for (size_t i = 0; i < size; ++i) {
    int const value = nums[i];
    if (value < bound2) {
      if (value < bound1) {
        ++counter1;
      } else {
        ++counter2;
      }
    } else {
      if (value < bound3) {
        ++counter3;
      } else {
        ++counter4;
      }
    }
  }
  return max(max(counter1, counter2), max(counter3, counter4));
}

main.cpp

#include <cstdlib>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>

void printUsage(char **argv) {
  std::cout << "Usage: " << argv[0] << " sorted | unsorted" << std::endl;
}

bool testSorted(int argc, char **argv) {
  if (argc != 2) {
    printUsage(argv);
    exit(EXIT_FAILURE);
  }
  std::string const arg(argv[1]);
  if (arg == "sorted") {
    return true;
  }
  if (arg == "unsorted") {
    return false;
  }
  printUsage(argv);
  exit(EXIT_FAILURE);
}

int test(int const *const nums, size_t const size, int const bound1, int const bound2, int const bound3);

volatile int dontThrowItAway;

int main(int argc, char **argv) {
  size_t const size = 64*1024;
  int const numOfRepetitions = 10*1000;
  int const bound1 = RAND_MAX / 4;
  bool const benchSorted = testSorted(argc, argv);

  std::clog << "Creating data..." << std::endl;
  std::vector<int> nums(size);
  generate(nums.begin(), nums.end(), rand);
  std::vector<int> sorted(nums);
  sort(sorted.begin(), sorted.end());

  std::clog << "Benching";
  if (benchSorted) {
    for (int i = 0; i < numOfRepetitions; ++i) {
      dontThrowItAway = test(&sorted[0], size, bound1, 2 * bound1, 3 * bound1);
      if ((i + 1) % (numOfRepetitions / 50) == 0) {
        std::clog << ".";
      }
    }
  } else {
    for (int i = 0; i < numOfRepetitions; ++i) {
      dontThrowItAway = test(&nums[0], size, bound1, 2 * bound1, 3 * bound1);
      if ((i + 1) % (numOfRepetitions / 50) == 0) {
        std::clog << ".";
      }
    }
  }
  std::clog << std::endl;
}

Makefile

bench: bench.o main.o
	g++ $^ -o $@

bench.o: bench.cpp
	g++ -c -o $@ $^

main.o: main.cpp
	g++ -c -O3 -o $@ $^