C language multi-thread programming learning

Reference video

https://www.bilibili.com/video/BV1kt411z7ND/?spm_id_from=333.1007.top_right_bar_window_history.content.click&vd_source=6c5d3cd50fc7fa8732bdfb760a055839

pthread installation course:

1

https://blog.csdn.net/qq_33194301/article/details/104879626?spm=1001.2101.3001.6661.1&depth_1-utm_relevant_index=1

1

https://blog.csdn.net/cuicui_ruirui/article/details/106782911?ops_request_misc=&request_id=&biz_id=102&spm=1018.2226.3001.4187

1 Create a thread

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")
void* myfunc(void* args) {
    
    
	int i;
	for (int i = 0; i <= 50; i++) {
    
    
		printf("%d\n", i);
	}
	return NULL;
}

int main() {
    
    
	pthread_t th1;
	pthread_t th2;
	pthread_create(&th1, NULL, myfunc, NULL);
	pthread_create(&th2, NULL, myfunc, NULL);
	pthread_join(th1, NULL);	
	pthread_join(th2 ,NULL);
	return 0;
}

2 Create thread

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")
void* myfunc(void* args) {
    
    
	int i;
	char* name = (char*)args;
	for (int i = 0; i <= 50; i++) {
    
    
		printf("%s: %d\n",name, i);
	}
	return NULL;
}

int main() {
    
    
	pthread_t th1;
	pthread_t th2;
	pthread_create(&th1, NULL, myfunc, "th1");  //第四个参数是,传入调用函数的参数
	pthread_create(&th2, NULL, myfunc, "th2");
	pthread_join(th1, NULL);
	pthread_join(th2, NULL);
	return 0;
}

2: Multi-thread summation

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")

typedef struct {
    
    
	int first;
	int last;
	int result;
}MY_ARGS;

int arr[5000];
int s1 = 0;
int s2 = 0;

void* myfunc(void* args) {
    
    
	int i;
	int s = 0;
	MY_ARGS* my_args = (MY_ARGS*)args;
	int fisrt = my_args->first;
	int last = my_args->last;

	for (int i = fisrt; i <= last; i++) {
    
    
		s = s + arr[i];
	}

	my_args->result = s;
	return NULL;
}

int main() {
    
    

	int i;
	for (int i = 0; i < 5000; i++)
	{
    
    
		arr[i] = rand() % 50;
	}


	pthread_t th1;
	pthread_t th2;

	MY_ARGS args1 = {
    
     0,2500,0 };
	MY_ARGS args2 = {
    
     2500,5000,0 };

	pthread_create(&th1, NULL, myfunc, &args1);  //第四个参数是,传入调用函数的参数
	pthread_create(&th2, NULL, myfunc, &args2);
	pthread_join(th1, NULL);
	pthread_join(th2, NULL);

	int s1 = args1.result;
	int s2 = args2.result;
	printf("s1=%d\n", s1);
	printf("s2=%d\n", s2);
	printf("s1 + s2= %d\n", s1);
	 

	return 0;
}

3: Lecture 3: Thread synchronization issues

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")

#define MAX_SIZE 50000000

int s = 0;

void* myfunc(void* args) {
    
    
	int i = 0;
	for (int i = 0; i < 100000000; i++){
    
    
		s++;
	}
	return 0;
}

int main() {
    
    

	pthread_t th1;
	pthread_t th2;
	
	pthread_create(&th1, NULL, myfunc, NULL);
	pthread_create(&th2, NULL, myfunc, NULL);

	pthread_join(th1, NULL);
	pthread_join(th2, NULL);

	printf("s= %d\n", s);

	return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")

#define MAX_SIZE 50000000

int s = 0;

pthread_mutex_t lock;

void* myfunc(void* args) {
    
    
	
	int i = 0;
	for (int i = 0; i < 100000000; i++){
    
    
		pthread_mutex_lock(&lock);
		s++;
		pthread_mutex_unlock(&lock);
	}
	return 0;
}

int main() {
    
    

	pthread_t th1;
	pthread_t th2;
	
	pthread_mutex_init(&lock, NULL);

	pthread_create(&th1, NULL, myfunc, NULL);
	pthread_create(&th2, NULL, myfunc, NULL);

	pthread_join(th1, NULL);
	pthread_join(th2, NULL);

	printf("s= %d\n", s);

	return 0;
}

After locking, the result is correct

example5

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#pragma comment(lib, "pthreadVC2.lib")

#define MAX_SIZE 50000000

typedef struct {
    
    
	int first;
	int last;
	int id;
} MY_ARGS;

int* arr;
int result[2];

void* myfun(void* args) {
    
    
	int i;
	MY_ARGS* my_args = (MY_ARGS*)args;
	int first = my_args->first;
	int last = my_args->last;
	int id = my_args->id;

	for (int i = first; i < last; i++)
	{
    
    
		result[id] = result[id] + arr[i];
	}
	return NULL;
}
int main() {
    
    
	int i;
	arr = malloc(sizeof(int)*MAX_SIZE);
	for (i = 0; i < MAX_SIZE; i++) {
    
    
		arr[i] = rand() % 5;
	}
	result[0] = 0;
	result[1] = 1;

	pthread_t th1;
	pthread_t th2;

	int mid = MAX_SIZE / 2;
	MY_ARGS args1 = {
    
     0,mid,0};
	MY_ARGS args2 = {
    
     mid,MAX_SIZE,1 };

	pthread_create(&th1, NULL, myfun, &args1);
	pthread_create(&th2, NULL, myfun, &args2);

	pthread_join(th1, NULL);
	pthread_join(th2, NULL);

	printf("result0 is:%d \n", result[0]);
	printf("result1 is:%d \n", result[1]);
	printf("sum of result is: %d", (result[0] + result[1]));
	return 0;
}

example6

? Why is example6 faster than example5?

Fake sharing