C:pthread的性能，比单线程低

我对我的代码的性能感到困惑，在处理单线程时，它只使用 13 秒，但它会消耗 80 秒。我不知道矢量是否一次只能由一个线程访问，如果是这样，我可能必须使用结构数组而不是矢量来存储数据，有人可以帮忙吗？

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <iterator>
#include <string>
#include <ctime>
#include <bangdb/database.h>
#include "SEQ.h"
#define NUM_THREADS 16
using namespace std;

typedef struct _thread_data_t {
std::vector<FDT> *Query;
unsigned long start;
unsigned long end;
connection* conn;
int thread;
} thread_data_t;

void *thr_func(void *arg) {
thread_data_t *data = (thread_data_t *)arg;
std::vector<FDT> *Query = data->Query;
unsigned long start = data->start;
unsigned long end = data->end;
connection* conn = data->conn;
printf("thread %d started %lu -> %lun", data->thread, start, end);
for (unsigned long i=start;i<=end ;i++ )
{
FDT *fout = conn->get(&((*Query).at(i)));
if (fout == NULL)
{
//printf("%stNULLn", s);
}
else
{
printf("Thread:%dt%sn", data->thread, fout->data);
}
}
pthread_exit(NULL);
}

int main(int argc, char *argv[])
{
if (argc<2)
{
printf("USAGE: ./seq <.txt>n");
printf("/home/rd/SCRIPTs/12X18610_L5_I052.R1.clean.code.seqn");
exit(-1);
}
printf("%sn", argv[1]);
vector<FDT> Query;
FILE* fpin;
if((fpin=fopen(argv[1],"r"))==NULL)  {
printf("Can't open Input file %sn", argv[1]);
return -1; 
}
char *key = (char *)malloc(36);
while (fscanf(fpin, "%s", key) != EOF)
{
SEQ * sequence = new SEQ(key);
FDT *fk = new FDT( (void*)sequence, sizeof(*sequence) );
Query.push_back(*fk);
}
unsigned long Querysize = (unsigned long)(Query.size());
std::cout << "myvector stores " << Querysize << " numbers.n";

//create database, table and connection
database* db = new database((char*)"berrydb");
//get a table, a new one or existing one, walog tells if log is on or off
table* tbl = db->gettable((char*)"hg19", JUSTOPEN);
if(tbl == NULL)
{
printf("ERROR:table NULL error");
exit(-1);
}
//get a new connection
connection* conn = tbl->getconnection();
if(conn == NULL)
{
printf("ERROR:connection NULL error");
exit(-1);
}
cerr<<"begin querying...n";

time_t begin, end;
double duration;
begin = clock();


unsigned long ThreadDealSize = Querysize/NUM_THREADS;
cerr<<"Querysize:"<<ThreadDealSize<<endl;

pthread_t thr[NUM_THREADS];
int rc;
thread_data_t thr_data[NUM_THREADS];
for (int i=0;i<NUM_THREADS ;i++ )
{
unsigned long ThreadDealStart = ThreadDealSize*i;
unsigned long ThreadDealEnd   = ThreadDealSize*(i+1) - 1;
if (i == (NUM_THREADS-1) )
{
ThreadDealEnd = Querysize-1;
}
thr_data[i].conn = conn;
thr_data[i].Query = &Query;
thr_data[i].start = ThreadDealStart;
thr_data[i].end = ThreadDealEnd;
thr_data[i].thread = i;
}

for (int i=0;i<NUM_THREADS ;i++ )
{
if (rc = pthread_create(&thr[i], NULL, thr_func, &thr_data[i]))
{
fprintf(stderr, "error: pthread_create, rc: %dn", rc);
return EXIT_FAILURE;
}
}

for (int i = 0; i < NUM_THREADS; ++i) {
pthread_join(thr[i], NULL);
}

cerr<<"donen"<<endl;
end = clock();
duration = double(end - begin) / CLOCKS_PER_SEC;
cerr << "runtime:   " << duration << "n" << endl;
db->closedatabase(OPTIMISTIC);
delete db;
printf("Donen");

return EXIT_SUCCESS;
}