我一直在使用pthreads,但已经意识到如果我使用1个线程,或者如果我将任务分解为1/N的N,我的代码将独立地花费相同的时间量线程。为了举例说明我我的代码减少到这个例子:同时采用单线程和多线程代码
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <boost/progress.hpp>
#define SIZEEXEC 200000000
using namespace boost;
using std::cout;
using std::endl;
typedef struct t_d{
int intArg;
} Thread_data;
void* function(void *threadarg)
{
Thread_data *my_data= (Thread_data *) threadarg;
int size= my_data->intArg;
int i=0;
unsigned rand_state = 0;
for(i=0; i<size; i++) rand_r(&rand_state);
return 0;
}
void withOutThreads(void)
{
Thread_data* t1= new Thread_data();
t1->intArg= SIZEEXEC/3;
function((void *) t1);
Thread_data* t2= new Thread_data();
t2->intArg= SIZEEXEC/3;
function((void *) t2);
Thread_data* t3= new Thread_data();
t3->intArg= SIZEEXEC/3;
function((void *) t3);
}
void withThreads(void)
{
pthread_t* h1 = new pthread_t;
pthread_t* h2 = new pthread_t;
pthread_t* h3 = new pthread_t;
pthread_attr_t* atr = new pthread_attr_t;
pthread_attr_init(atr);
pthread_attr_setscope(atr,PTHREAD_SCOPE_SYSTEM);
Thread_data* t1= new Thread_data();
t1->intArg= SIZEEXEC/3;
pthread_create(h1,atr,function,(void *) t1);
Thread_data* t2= new Thread_data();
t2->intArg= SIZEEXEC/3;
pthread_create(h2,atr,function,(void *) t2);
Thread_data* t3= new Thread_data();
t3->intArg= SIZEEXEC/3;
pthread_create(h3,atr,function,(void *) t3);
pthread_join(*h1,0);
pthread_join(*h2,0);
pthread_join(*h3,0);
pthread_attr_destroy(atr);
delete h1;
delete h2;
delete h3;
delete atr;
}
int main(int argc, char *argv[])
{
bool multThread= bool(atoi(argv[1]));
if(!multThread){
cout << "NO THREADS" << endl;
progress_timer timer;
withOutThreads();
}
else {
cout << "WITH THREADS" << endl;
progress_timer timer;
withThreads();
}
return 0;
}
无论是编码是错误的或有对我的系统不允许进行并行处理的东西。我在Ubuntu 11.10上运行x86_64-linux-gnu,gcc 4.6,英特尔®至强®CPU E5620 @ 2.40GHz×4
感谢您的任何建议! (1)progress_timer计时器不允许我测量“真实”时间的差异,以及(2)我在“功能”中给出的任务似乎不是足以让我的机器用1或3个线程给出不同的时间(这很奇怪,在这两种情况下我都会有10秒的时间...)。我试图分配内存,使它更重,是的,我看到了一个区别。虽然我的其他代码更复杂,但它仍然有很好的机会运行+ - 同时有1或3个线程。谢谢!
'功能'实际上*做*什么?编译器是否有可能优化所有东西? – 2012-04-25 13:06:03
另外,请注意,您并未使用一致的“intArg”值。 – 2012-04-25 13:06:52
您是否正在进行优化或不进行优化? – Tobias 2012-04-25 13:09:00