xref: /recipes/topk/word_freq_shards_basic.cc

/* sort word by frequency, sharding version.

  1. read input file, shard to N files:
       word
  2. assume each shard file fits in memory, read each shard file, count words and sort by count, then write to N count files:
       count \t word
  3. merge N count files using heap.

Limits: each shard must fit in memory.
*/

#include <assert.h>

#include "file.h"
#include "merge.h"
#include "timer.h"

#include "absl/container/flat_hash_map.h"
#include "absl/hash/hash.h"
#include "absl/strings/str_format.h"
#include "muduo/base/Logging.h"
#include "muduo/base/ThreadPool.h"

#include <algorithm>
#include <memory>
#include <string>
#include <unordered_map>
#include <vector>

#include <fcntl.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

using absl::string_view;
using std::string;
using std::vector;
using std::unique_ptr;

int kShards = 10, kThreads = 4;
bool g_verbose = false, g_keep = false;
const char* shard_dir = ".";
const char* g_output = "output";

class Sharder // : boost::noncopyable
{
 public:
  Sharder()
    : files_(kShards)
  {
    for (int i = 0; i < kShards; ++i)
    {
      char name[256];
      snprintf(name, sizeof name, "%s/shard-%05d-of-%05d", shard_dir, i, kShards);
      files_[i].reset(new OutputFile(name));
    }
    assert(files_.size() == static_cast<size_t>(kShards));
  }

  void output(string_view word)
  {
    size_t shard = hash(word) % files_.size();
    files_[shard]->appendRecord(word);
  }

  void finish()
  {
    int shard = 0;
    for (const auto& file : files_)
    {
      // if (g_verbose)
      printf("  shard %d: %ld bytes, %ld items\n", shard, file->tell(), file->items());
      ++shard;
      file->close();
    }
  }

 private:
  absl::Hash<string_view> hash;
  vector<unique_ptr<OutputFile>> files_;
};

int64_t shard_(int argc, char* argv[])
{
  Sharder sharder;
  Timer timer;
  int64_t total = 0;
  for (int i = optind; i < argc; ++i)
  {
    LOG_INFO << "Processing input file " << argv[i];
    double t = Timer::now();
    string line;
    InputFile input(argv[i]);
    while (input.getline(&line))
    {
      sharder.output(line);
    }
    size_t len = input.tell();
    total += len;
    double sec = Timer::now() - t;
    LOG_INFO << "Done file " << argv[i] << absl::StrFormat(" %.3f sec %.2f MiB/s", sec, len / sec / 1024 / 1024);
  }
  sharder.finish();
  LOG_INFO << "Sharding done " << timer.report(total);
  return total;
}

// ======= count_shards =======

void count_shard(int shard, int fd, size_t len)
{
  Timer timer;

  double t = Timer::now();
  LOG_INFO << absl::StrFormat("counting shard %d: input file size %ld", shard, len);
  {
  void* mapped = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
  assert(mapped != MAP_FAILED);
  const uint8_t* const start = static_cast<const uint8_t*>(mapped);
  const uint8_t* const end = start + len;

  // std::unordered_map<string_view, uint64_t> items;
  absl::flat_hash_map<string_view, uint64_t> items;
  int64_t count = 0;
  for (const uint8_t* p = start; p < end;)
  {
    string_view s((const char*)p+1, *p);
    items[s]++;
    p += 1 + *p;
    ++count;
  }
  LOG_INFO << "items " << count << " unique " << items.size();
  if (g_verbose)
  printf("  count %.3f sec %ld items\n", Timer::now() - t, items.size());

  t = Timer::now();
  vector<std::pair<size_t, string_view>> counts;
  for (const auto& it : items)
  {
    if (it.second > 1)
      counts.push_back(std::make_pair(it.second, it.first));
  }
  if (g_verbose)
  printf("  select %.3f sec %ld\n", Timer::now() - t, counts.size());

  t = Timer::now();
  std::sort(counts.begin(), counts.end());
  if (g_verbose)
  printf("  sort %.3f sec\n", Timer::now() - t);

  t = Timer::now();
  int64_t out_len = 0;
  {
    char buf[256];
    snprintf(buf, sizeof buf, "count-%05d", shard);
    OutputFile output(buf);

    for (auto it = counts.rbegin(); it != counts.rend(); ++it)
    {
      output.write(absl::StrFormat("%d\t%s\n", it->first, it->second));
    }

    for (const auto& it : items)
    {
      if (it.second == 1)
      {
        output.write(absl::StrFormat("1\t%s\n", it.first));
      }
    }
    out_len = output.tell();
  }
  if (g_verbose)
  printf("  output %.3f sec %lu\n", Timer::now() - t, out_len);

  if (munmap(mapped, len))
    perror("munmap");
  }
  ::close(fd);
  LOG_INFO << "shard " << shard << " done " << timer.report(len);
}

void count_shards(int shards)
{
  assert(shards <= kShards);
  Timer timer;
  int64_t total = 0;
  muduo::ThreadPool threadPool;
  threadPool.setMaxQueueSize(2*kThreads);
  threadPool.start(kThreads);

  for (int shard = 0; shard < shards; ++shard)
  {
    char buf[256];
    snprintf(buf, sizeof buf, "%s/shard-%05d-of-%05d", shard_dir, shard, kShards);
    int fd = open(buf, O_RDONLY);
    assert(fd >= 0);
    if (!g_keep)
      ::unlink(buf);

    struct stat st;
    if (::fstat(fd, &st) == 0)
    {
      size_t len = st.st_size;
      total += len;
      threadPool.run([shard, fd, len]{ count_shard(shard, fd, len); });
    }
  }
  while (threadPool.queueSize() > 0)
  {
    LOG_DEBUG << "waiting for ThreadPool " << threadPool.queueSize();
    muduo::CurrentThread::sleepUsec(1000*1000);
  }
  threadPool.stop();
  LOG_INFO << "Counting done "<< timer.report(total);
}

// ======= merge =======

int main(int argc, char* argv[])
{
  /*
  int fd = open("shard-00000-of-00010", O_RDONLY);
  double t = Timer::now();
  int64_t len = count_shard(0, fd);
  double sec = Timer::now() - t;
  printf("count_shard %.3f sec %.2f MB/s\n", sec, len / sec / 1e6);
  */
  setlocale(LC_NUMERIC, "");

  int opt;
  int count_only = 0;
  int merge_only = 0;
  while ((opt = getopt(argc, argv, "c:km:o:p:s:t:v")) != -1)
  {
    switch (opt)
    {
      case 'c':
        count_only = atoi(optarg);
        break;
      case 'k':
        g_keep = true;
        break;
      case 'm':
        merge_only = atoi(optarg);
        break;
      case 'o':
        g_output = optarg;
        break;
      case 'p':  // Path for temp shard files
        shard_dir = optarg;
        break;
      case 's':
        kShards = atoi(optarg);
        break;
      case 't':
        kThreads = atoi(optarg);
        break;
      case 'v':
        g_verbose = true;
        break;
    }
  }

  if (count_only > 0 || merge_only)
  {
    g_keep = true;
    //g_verbose = true;
    count_only = std::min(count_only, kShards);

    if (count_only > 0)
    {
      count_shards(count_only);
    }

    if (merge_only > 0)
    {
      merge(merge_only);
    }
  }
  else
  {
    // Run all three steps
    Timer timer;
    LOG_INFO << argc - optind << " input files, " << kShards << " shards, "
             << "output " << g_output <<" , temp " << shard_dir;
    int64_t input = 0;
    input = shard_(argc, argv);
    count_shards(kShards);
    int64_t output_size = merge(kShards);
    LOG_INFO << "All done " << timer.report(input) << " output " << output_size;
  }
}