Pthread Read Text file

#include  <pthread.h> #include  <fstream> #include  <iostream> #include  < string> #include  <vector>using namespace std; #define  LINE_PER_THREAD  1024pthread_mutex_t count_mutex = pthread_mutex_initializer;struct param{     vector<string> vstr;    int offset;    int  tidx;};/ /kernel functionvoid * std_output (VOID&NBSP;*PA) {    struct param  *local =  (struct param *)  pa;    vector<string>  vstr = local->vstr;    int offset = local->offset;     int tidx = local->tidx;    pthread_mutex_lock (& Count_mutex);     int count = 0;    int i =  offset;    while (I < vstr.size ()  && i < offset + line_ Per_thread) {        count++;         i++;    }    cout <<  " thread "   << tidx <<   has   << count <<    Lines " << endl;    pthread_mutex_unlock (&count_mutex);} Int main () {    ifstream input_data ("input.txt");     int  line_num = 0;    string line;    vector<string > vstring;    while (Input_data.is_open ()) {         if (!input_data.eof ()) {             Getline (Input_data, line);            vstring.push_back (line);             line_num++;        }         else{             cout << line_num << endl;             break;        }     }    input_data.close ();     int thread_num =   (line_num + line_per_thread - 1)  / LINE_PER_THREAD;     pthread_t threads[thread_num];    for (int i = 0; i  < thread_num; i++) {        struct param *str_ Param = new param ();         str_param->vstr = vstring;         str_param->offset = i * LINE_PER_THREAD;         str_param->tidx = i;         pthread_create (&threads[i], NULL, std_output,  (void *)  str_param);     }    for (int i = 0; i < thread_num;  i++)         pthread_join (threads[i], null);     return 0;}

1. Read a text file, first count the number of lines of text;
   

2. By 1024 lines per line, calculate how many threads are required; When calculating, you can use the formula (n + 1023)/1024, where n is the total row number of the text file;

3. Std_output is a kernel function that uses a mutex lock, which determines which part of the data to process based on offset offsets. The program simply prints out how many rows are contained in a certain section.

Output:

18207
Thread 0 has 1024x768 lines
Thread 1 has 1024x768 lines
Thread 2 has 1024x768 lines
Thread 3 has 1024x768 lines
Thread 4 has 1024x768 lines
Thread 5 has 1024x768 lines
Thread 6 has 1024x768 lines
Thread 7 has 1024x768 lines
Thread 8 has 1024x768 lines
Thread 9 has 1024x768 lines
Thread Ten has 1024x768 lines
Thread one has 1024x768 lines
Thread has 1024x768 lines
Thread has 1024x768 lines
Thread + has 1024x768 lines
Thread has 1024x768 lines
Thread + has 1024x768 lines
Thread # has 799 lines

This article from "Hu A Knife" blog, declined reprint!

Pthread Read text file