in the following program, I am trying to create M threads, each of which open a file called filexxxxin . for exmaple 4th thread will open file file0003.in.
When I run the program, it open the client0001 file for all threads. Any body knows what's wrong with my code.
appreciate your help. -
#include <netdb.h>
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#include <netinet/in.h>
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#include <unistd.h>
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#include <iostream>
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#include <pthread.h>
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#include <sys/types.h>
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#include <ctype.h>
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#include <fstream.h>
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using namespace std;
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void *client_function(void *);
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int main()
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{
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int M;
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pthread_t *client;
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cout << "Enter the number of hosts: " << endl;
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cin >> M;
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//create M thread to simulate M clients
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//dynamically allocate threads
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client = new pthread_t[M];
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for(int i = 0 ; i < M ; i++)
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{
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//create M threads
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pthread_create( &(client[i]) , NULL, client_function , &i);
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cout << "thread " << i+1 << " created." << endl;
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}
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//join the threads
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for(int i = 0 ; i < M ; i++)
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{
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pthread_join(client[i] , NULL);
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}
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}
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/****************************************************************/
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void *client_function(void *input_value)
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{
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int *i;
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int temp;
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char line[12];
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ifstream infile;
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i = static_cast<int *>(input_value);
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temp = *i + 1;
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sprintf(line, "file%04d.in", temp);
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infile.open(line);
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if(!infile.is_open())
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{
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cout << "cannot open the file " << line << endl;
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exit(0);
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}
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else
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cout << "the file " << line << " succesfully opened." << endl;
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}
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2  17427 
in the following program, I am trying to create M threads, each of which open a file called filexxxxin . for exmaple 4th thread will open file file0003.in.
When I run the program, it open the client0001 file for all threads. Any body knows what's wrong with my code.
appreciate your help.
Might be due to the fact you are passing the pointer to a local variable to the other threads. Then you change that variable. Any number of random things could happen. Try passing a new int(i) instead. And don't forget to clean up the passed int in the thread it is passed to.
Adrian
Might be due to the fact you are passing the pointer to a local variable to the other threads. Then you change that variable. Any number of random things could happen. Try passing a new int(i) instead. And don't forget to clean up the passed int in the thread it is passed to.
Adrian
Alternatively, you can wait on a 'semaphore'[*] after spawning the thread. The thread would be responsible to release the 'semaphore'. Doing it this way would force the new thread to execute, store the i value and give control back to the parent thread.
Adrian
[*]sorry, pthreads uses a different name which is lighter weight for threads, semaphores are usually used for interprocess communication, I just can't remember the name at the moment
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