MPI::Init(argc,argv);
 cout << " INFO init done" << endl;
 int myrank = MPI::COMM_WORLD.Get_rank();
 int numprocs = MPI::COMM_WORLD.Get_size();
 get_filename(path_name, myrank);
 cout << " INFO open file : " << path_name << endl;
 MPI::File thefile = MPI::File::Open(MPI::COMM_WORLD, path_name.c_str(),
                  MPI::MODE_RDONLY,
                  MPI::INFO_NULL);
 MPI::Offset offset = 101;
 MPI::Offset limit = thefile.Get_size();
 cout << " INFO go computing" << endl;
 do {
   thefile.Read_at(offset, buf, bufsize, MPI_CHAR, status);
   temp.assign(buf);
   Tokenize(temp,tokens,"n");
   line.assign(tokens.at(0));
   tokens.clear();

   Tokenize(line,tokens,"t");
   nidt_count(tokens);
   tokens.clear();
   offset += (line.size() + 1);
 }while(offset < limit);
 count = status.Get_count(MPI_INT);
 cout << "process " << myrank << " reads " << nidt_hash.size() << " nidt" << endl;

ID        DATE             NUM_1        NUM_2     NB_UNITE TYPUNIT CODE_1 CODE_2

0  2007-05-13 15:37:48  33671624244  33698802900    547      s       0      17
0  2007-05-13 15:52:22  33671624244  33672211799      5      s       0      17
....

CODE_1 CODE_2 CODEVAL

  0       17     VS
  0       34     SS

Select CODEVAL, hour(date) AS HEURE, COUNT(*) AS NBSMSSOR
From Tables_1 Join CODEVAL using(CODE_1,CODE_2)
Where CODEVAL='SS'

value -> {r | r is a byteOffset of a row that has "value" in the index column}