Multiple thread pause/resume - c++

Question

Main thread uses group of threads to search. First solution (test1) is often creating , waiting - join() and destroying threads. This works but has overhead. I try using mutex and condition_variable, but this not works,. especially for number searching threads>1.
My code:
#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <vector>
using namespace std;
const int NThr = 2;
struct InterchangeData {
bool endflag=false;
mutex chg_mutex;
condition_variable condition;
};
InterchangeData data;
bool execute1(InterchangeData* xchgData) {
for (int i=0; i<10; i++) {
if (xchgData->endflag) return false;
this_thread::sleep_for(chrono::milliseconds(rand()%10 +1 ));
if (rand()%100 == 50) {
lock_guard<mutex> lock(xchgData->chg_mutex);
if (!xchgData->endflag) {
printf("found!");
xchgData->endflag = true;
return true;
}
}
}
return false;
}
bool execute2(InterchangeData* xchgData) {
while (true) {
{
unique_lock<mutex> lock(xchgData->chg_mutex);
xchgData->condition.wait(lock);
}
int ret=2;
if (xchgData->endflag) ret=0;
if (execute1(xchgData)) ret=1;
{
unique_lock<mutex> lock(xchgData->chg_mutex);
xchgData->condition.notify_one();
this_thread::sleep_for(chrono::milliseconds(1));
if (ret==0) return false;
else if (ret==1) return true;
}
}
}
vector<thread*> threads;
typedef bool (*functype)(InterchangeData*);
void start(functype execute) {
for (int i=0; i<NThr; i++) {
auto t = new thread(execute, &data);
threads.push_back(t);
}
}
void stop() {
for (auto t : threads) {
t->join();
delete t;
}
threads.clear();
}
void test1() {
for (int i=0; i<10; i++) {
start(&execute1);
stop();
}
}
void test2() {
start(&execute2);
this_thread::sleep_for(chrono::milliseconds(100));
for (int i=0; i<10; i++) {
{
unique_lock<mutex> lock(data.chg_mutex);
data.condition.notify_one();
this_thread::sleep_for(chrono::milliseconds(1));
}
{
unique_lock<mutex> lock(data.chg_mutex);
data.condition.wait(lock);
}
}
{
unique_lock<mutex> lock(data.chg_mutex);
data.condition.notify_one();
this_thread::sleep_for(chrono::milliseconds(1));
}
stop();
}
int main() {
test2();
return 0;
}
Problem: is possible fast pausing/resuming execute function and main thread using condition_variable,unique_lock and wait/notify_one ?