線程是進程中的執行流

線程比進程更節省資源.
線程間的通信比進程間的通信代價小得多.

#include<sys/types.h> #include<unistd.h> #include<stdio.h> #include<pthread.h>// 線程函數 void* threadFunc(void* arg){sleep(3);printf("In NEW thread\n"); }int main(){pthread_t tid; // 線程id// 線程創建函數pthread_create(&tid,NULL,threadFunc,NULL);printf("In main thread\n");// 等待指定的線程tid結束pthread_join(tid,NULL);return 0; } #include<sys/types.h> #include<unistd.h> #include<stdio.h> #include<pthread.h> #include<time.h> #include<stdlib.h>int value = 100; // 多個線程共享的數據, 屬于進程// 線程函數 void* hello(void* arg){for(int i=0; i<3;i++){printf("hello(%d)\n",value++);sleep(1);} }// 線程函數 void* world(void* arg){for(int i=0; i<3;i++){printf("world(%d)\n",value++);sleep(2);} }int main(){// srand(time(NULL));pthread_t tid, tid2;pthread_create(&tid,NULL,hello,NULL);pthread_create(&tid2,NULL,world,NULL);pthread_join(tid,NULL);pthread_join(tid2,NULL);printf("In main thread(%d)\n",value); }

#include<sys/types.h> #include<unistd.h> #include<stdio.h> #include<pthread.h> #include<time.h> #include<stdlib.h> #include<math.h> #include<omp.h>void* calculate_pi(void* arg){unsigned int seed = time(NULL);int circle_points = 0;int square_points = 0;int interval = *((int*)arg); // 傳遞的參數for(int i = 0; i<interval*interval; ++i){double rand_x = (double)rand_r(&seed)/RAND_MAX;double rand_y = (double)rand_r(&seed)/RAND_MAX;if((rand_x*rand_x + rand_y*rand_y) <= 1){circle_points++;}square_points++;}double pi = (double)(4.0*circle_points)/square_points;printf("The estimated PI is %lf in %d times\n",pi,interval*interval);pthread_exit(0); // 表示一個線程結束，0表示正常退出 }int main(int argc, char const *argv[]){clock_t start,delta;double time_used;start = clock();pthread_t calculate_pi_threads[10];int args[10];for(int i=0; i<10; i++){args[i] = 1000*(i+1);// 連續創建多個線程pthread_create(calculate_pi_threads+i,NULL,calculate_pi,args+i);}for(int i=0; i<10; i++){// 等待每一個線程結束pthread_join(calculate_pi_threads[i],NULL);}// 等所有線程運行結束，才會執行到這里delta = clock() - start;printf("The time taken in total: %lf seconds\n", (double)delta/CLOCKS_PER_SEC);return 0; }

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