> I see from the linked page that Kyoto Cabinet itself now has a successor which is Tkrzw.

I found time to try the Tkrzw C++ library. Tkrzw provides sharding capabilities. Spoiler alert... It's awesome :)

C++ bits:

#include <tkrzw_dbm_hash.h>
#include <tkrzw_dbm_shard.h>

...

// tkrzw::HashDBM dbm;
// dbm.Open("/dev/shm/casket.tkh", true).OrDie();

   tkrzw::ShardDBM dbm;

   const std::map<std::string, std::string> params = {
     {"num_shards", "8"}, {"dbm", "HashDBM"} };

   dbm.OpenAdvanced("/dev/shm/casket.tkh", true, tkrzw::File::OPEN_DEF
+AULT, params);

   for (int i = 0; i < nfiles; ++i)
      get_properties(fname[i], nthds, dbm);

   dbm.Close();
[download]

ls -1 /dev/shm

casket.tkh-00000-of-00008
casket.tkh-00001-of-00008
casket.tkh-00002-of-00008
casket.tkh-00003-of-00008
casket.tkh-00004-of-00008
casket.tkh-00005-of-00008
casket.tkh-00006-of-00008
casket.tkh-00007-of-00008
[download]

I will come back after completing a new llil4shard C++ variant. The Tkrzw library is amazing. In the meantime, the left column is the number of shards processing 26 big files (48 CPU threads). Total: 91,395,200 lines, 79,120,065 unique keys. For reference, Perl lliltch.pl "get properties" takes 9.533 seconds; 128 maps (or shards).

  8 shards : 11.958 secs   7.643 mil QPS
 16 shards :  6.680 secs  13.682 mil QPS
 32 shards :  4.424 secs  20.659 mil QPS
 64 shards :  3.419 secs  26.732 mil QPS
 96 shards :  3.052 secs  29.946 mil QPS
128 shards :  2.903 secs  31.483 mil QPS
[download]

Yay :) Tkrzw provides the increment method. Like Kyoto Cabinet, the value is stored as an 8-byte big-endian integer.

#include <byteswap.h>

...

// Process max Nthreads chunks concurrently.
while (first < last) {
   char* beg_ptr{first};   first = find_char(first, last, '\n');
   char* end_ptr{first};   ++first;

   if ((found = find_char(beg_ptr, end_ptr, '\t')) == end_ptr)
      continue;

   count = fast_atoll64(found + 1);
   klen  = std::min(MAX_STR_LEN_L, (size_t)(found - beg_ptr));

   std::basic_string_view<char> key{
      reinterpret_cast<const char*>(beg_ptr), klen };

   dbm_ret.IncrementSimple(key, count);

   // std::string value = dbm_ret.GetSimple(key);
   // int64_t *bigendian_num = reinterpret_cast<int64_t*>(value.data()
+);
   // std::cout << key << ": " << bswap_64(*bigendian_num) << "\n";
}
[download]

So much learning from the Long List is Long series :) Notice above, no locking among threads for incrementing the count. No local hash either. The "IncrementSimple" method is a single operation. I tested retrieval and conversion, which will be done later in the code.

Update: Iteration is slow

   // Store the properties into a vector
   vec_str_int_type propvec; propvec.reserve(num_keys);

   std::string key, value;
   int64_t *bigendian_num = reinterpret_cast<int64_t*>(value.data());
   std::unique_ptr<tkrzw::DBM::Iterator> iter = dbm.MakeIterator();

   iter->First();
   while (iter->Get(&key, &value) == tkrzw::Status::SUCCESS) {
      propvec.emplace_back(key, bswap_64(*bigendian_num));
      iter->Next();
   }
   dbm.Close();
[download]

Notice "tkrzw to vector". I will try again later and iterate the individual maps (or shards) in parallel.

$ NUM_THREADS=8 NUM_MAPS=4 ./llil4tkh big{1,2,3}.txt | cksum
llil4tkh (fixed string length=12) start
use OpenMP
use boost sort
get properties         2.978 secs
shardDBM to vector     5.848 secs
vector stable sort     0.157 secs
write stdout           0.213 secs
total time             9.197 secs
2956888413 93308427
[download]

Compared to Perl using Tokyo Cabinet :)

$ perl llilthc.pl --threads=8 --maps=4 big{1,2,3}.txt | cksum
Tokyo Cabinet hash database - start
fixed string length=12, threads=8, maps=4
get properties   :     5.487 secs
pack properties  :     3.545 secs
sort packed data :     0.969 secs
write stdout     :     0.764 secs
total time       :    10.769 secs
    count lines  : 10545600
    count unique : 10367603
2956888413 93308427
[download]

Update: Parallel iteration

This works :), to make iteration faster. Iterate all the maps (or shards) in parallel. Append to the property vector, serially.

   // Store the properties into a vector
   vec_str_int_type propvec; propvec.reserve(num_keys);

   #pragma omp parallel for schedule(static, 1)
   for (int i = 0; i < nmaps; ++i) {

      // casket.tkh-00000-of-00004
      // casket.tkh-00001-of-00004
      // casket.tkh-00002-of-00004
      // casket.tkh-00003-of-00004

      char path[255];
      std::sprintf(path, "/dev/shm/casket.tkh-%05d-of-%05d", i, nmaps)
+;
      tkrzw::HashDBM dbm; dbm.Open(path, false).OrDie();
      int64_t num_keys = dbm.CountSimple();

      if (num_keys > 0) {
         vec_str_int_type locvec; locvec.reserve(num_keys);

         std::string key, value;
         int64_t *bigendian_num = reinterpret_cast<int64_t*>(value.dat
+a());
         std::unique_ptr<tkrzw::DBM::Iterator> iter = dbm.MakeIterator
+();

         iter->First();
         while (iter->Get(&key, &value) == tkrzw::Status::SUCCESS) {
            locvec.emplace_back(key, bswap_64(*bigendian_num));
            iter->Next();
         }

         #pragma omp critical
         propvec.insert(
            // Append local vector to propvec
            propvec.end(),
            std::make_move_iterator(locvec.begin()),
            std::make_move_iterator(locvec.end())
         );
      }

      dbm.Close();
   }
[download]

Results:

$ NUM_THREADS=8 NUM_MAPS=4 ./llil4tkh big{1,2,3}.txt | cksum
llil4tkh (fixed string length=12) start
use OpenMP
use boost sort
get properties         2.985 secs
shardDBM to vector     1.381 secs
vector stable sort     0.157 secs
write stdout           0.214 secs
total time             4.739 secs
2956888413 93308427

$ NUM_THREADS=8 NUM_MAPS=8 ./llil4tkh big{1,2,3}.txt | cksum
llil4tkh (fixed string length=12) start
use OpenMP
use boost sort
get properties         2.106 secs
shardDBM to vector     0.683 secs
vector stable sort     0.159 secs
write stdout           0.208 secs
total time             3.157 secs
2956888413 93308427

$ NUM_THREADS=8 NUM_MAPS=32 ./llil4tkh big{1,2,3}.txt | cksum
llil4tkh (fixed string length=12) start
use OpenMP
use boost sort
get properties         1.364 secs
shardDBM to vector     0.639 secs
vector stable sort     0.159 secs
write stdout           0.207 secs
total time             2.372 secs
2956888413 93308427
[download]

Let's try processing 26 big files :) Get properties is 3 times faster than Perl. The QPS is measured by count_lines and count_unique, respectively, divided by time: in millions.

$ perl lliltch.pl --threads=48 --maps=max in/biga* | cksum
Tokyo Cabinet hash database - start
fixed string length=12, threads=48, maps=128
get properties   :     9.533 secs    9.587 mil QPS
pack properties  :     3.276 secs   24.151 mil QPS
sort packed data :     6.826 secs
write stdout     :     1.631 secs
total time       :    21.284 secs
    count lines  : 91395200
    count unique : 79120065
2005669956 712080585

$ NUM_THREADS=48 NUM_MAPS=128 ./llil4tkh in/biga* | cksum
llil4tkh (fixed string length=12) start
sharding managed by the tkrzw::ShardDBM library
use OpenMP
use boost sort
get properties         2.872 secs   31.823 mil QPS
shardDBM to vector     1.546 secs   51.177 mil QPS
vector stable sort     1.399 secs
write stdout           1.561 secs
total time             7.380 secs
2005669956 712080585
[download]

Thank you, hippo for mentioning the Tkrzw C++ library. I'm one step away before posting the new llil variant. Currently, the db path is hard-coded to "/dev/shm/casket.tkh".

Update: app-level sharding

For better performance, I tried constructing an array of "tkrzw::HashDBM" objects versus a single "tkrzw::ShardDBM" object. This requires the application to compute the hash value, which is not a problem. Below, see timings for app-level sharding.

$ NUM_THREADS=48 NUM_MAPS=128 ./llil4tkh2 in/biga* | cksum
llil4tkh2 (fixed string length=12) start
sharding managed by the application
use OpenMP
use boost sort
get properties         2.337 secs   39.108 mil QPS
hashDBMs to vector     1.607 secs   49.235 mil QPS
vector stable sort     1.379 secs
write stdout           1.576 secs
total time             6.900 secs
2005669956 712080585
[download]

Update: MAX_STR_LEN_L optimization

Notice "vector stable sort" completing in half the time. The code is final and will post two Tkrzw variants this evening {one sharding by the C++ library, another application-level sharding}.

$ NUM_THREADS=48 NUM_MAPS=128 ./llil4tkh2 in/biga* | cksum
llil4tkh2 (fixed string length=12) start
sharding managed by the application
use OpenMP
use boost sort
get properties         2.331 secs   39.209 mil QPS
hashDBMs to vector     1.420 secs   55.718 mil QPS
vector stable sort     0.663 secs
write stdout           1.541 secs
total time             5.957 secs
2005669956 712080585
[download]