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Programming
Multiplying 2D arrays using fork()
Post 302608809 by giampoul on Sunday 18th of March 2012 05:31:41 PM
03-18-2012
Quote:
Code:
//multiply a[2][3] * b[3][4] = c[2][4]
//with fork
//each child completes one c[2][4]'s row
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
main()
{
int a[2][3]={1,2,3,
4,5,6};
int b[3][4]={1,2,3,4,
5,6,7,8,
9,10,11,12};
int c[2][4];
int i,j;
int m[4]; //for the calculation
int n; //common 3
int pid; //fork
int pipefd[2];
int w,r;
char buff[100];
char str[100+1]={'\0'};
int data_len;
int temp;
for(i=0;i<2;i++)
{
pipe(pipefd);
if(pipefd<0)
printf("Pipe error\n");
pid=fork();
if(pid==-1)
{
printf("Can't fork\n");
}
if(pid==0)//child
{
for(j=0;j<4;j++)
{
for(n=0;n<3;n++){m[n]=0;} //initialize m[4]
for(n=0;n<3;n++)
{
m[j]=m[j]+a[i][n]*b[n][j];
}
}
for(j=0;j<4;j++)
{
sprintf(str,"%d",m[j]);
w=write(pipefd[1],str,data_len);
}
exit(0);
}
if(pid>0)//parent
{
wait(0);
for(i=0;i<4;i++)
{
m[i]=read(pipefd[0], buff, sizeof(buff));
}
}
}
printf("C:\n");
for(i=0;i<2;i++)
{
for(j=0;j<4;j++)
{
printf("%d\t",c[i][j]);
}
printf("\n");
}
}By the way i get no compilng errors, but the program dont run...
I cant understand the use of snprintf()
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LEARN ABOUT OSX
pthread_atfork
PTHREAD_ATFORK(3) BSD Library Functions Manual PTHREAD_ATFORK(3) NAME
pthread_atfork -- register handlers to be called before and after fork() SYNOPSIS
#include <pthread.h> int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void)); DESCRIPTION
The pthread_atfork() function is used to register functions to be called before and after fork(). The prepare handler is called before fork(), while the parent and child handlers are called after fork() in the parent and child process respectively. The prepare handlers are called in reverse order of their registration, while parent and child handlers are called in the order in which they were registered. Any of the handlers may be NULL. Important: only async-signal-safe functions are allowed on the child side of fork(). See sigaction(2) for details. RETURN VALUES
If successful, the pthread_atfork() function will return zero; otherwise an error number will be returned to indicate the error. ERRORS
pthread_atfork() will fail if: [ENOMEM] The system lacked the necessary resources to add another handler to the list. SEE ALSO
fork(2) STANDARDS
pthread_atfork() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). BSD
August 12, 2004 BSD