Multiplying 2D arrays using fork() Post: 302607140

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Top Forums Programming Multiplying 2D arrays using fork() Post 302607140 by giampoul on Tuesday 13th of March 2012 06:12:24 PM

03-13-2012

Registered User

Multiplying 2D arrays using fork()

HI,
i am trying to multiply 2 2D arrays (a[2][3],b[3][4]) using fork.
The answer will be at c[2][4].
Each child have to calculate 1 row of c[2][4].
The code is right, as i think of it, with no errors but i dont get the correct c array...
I think there is maybe a mistake in i dimension ...
Anyway, here is the code:

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>

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;	//for the calculation
  int n;	//common 3
  int pid;	//fork
  
  for(i=0;i<2;i++)
  {
    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=m+a[i][n]*b[n][j];
	}
	c[i][j]=m;
	m=0;
      }
      exit(EXIT_SUCCESS);
    }
    if(pid>0)//parent
    {
      wait(0);
    }
  }
  printf("C:\n");
  for(i=0;i<2;i++)
  {
    for(j=0;j<4;j++)
    {
      printf("%d\t",c[i][j]);
    }
    printf("\n");
  }	       
}

Any help, please ?

giampoul

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LEARN ABOUT REDHAT

fork

FORK(2) 						     Linux Programmer's Manual							   FORK(2)

NAME

       fork - create a child process

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       pid_t fork(void);

DESCRIPTION

       fork  creates a child process that differs from the parent process only in its PID and PPID, and in the fact that resource utilizations are
       set to 0.  File locks and pending signals are not inherited.

       Under Linux, fork is implemented using copy-on-write pages, so the only penalty incurred by fork is the time and memory required to  dupli-
       cate the parent's page tables, and to create a unique task structure for the child.

RETURN VALUE

       On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of exe-
       cution.	On failure, a -1 will be returned in the parent's context, no child process will be created, and errno will be set appropriately.

ERRORS

       EAGAIN fork cannot allocate sufficient memory to copy the parent's page tables and allocate a task structure for the child.

       ENOMEM fork failed to allocate the necessary kernel structures because memory is tight.

CONFORMING TO

       The fork call conforms to SVr4, SVID, POSIX, X/OPEN, BSD 4.3.

SEE ALSO

       clone(2), execve(2), vfork(2), wait(2)

Linux 1.2.9							    1995-06-10								   FORK(2)

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