The task wast to sort in an ascending order the array from the input.dat, using fork and divide and conquer algorithm.
So i wrote a code using this, but the parent process end faster than the child. I have the following line in my code but the parents will not wait for their children.
while(wait(NULL)>0);
A little explanation for my code:
In the input.dat is an array with the following form:
(long of the array) (space) (first number) (space) (second number) ...
example:
6 2 3 1 4 5 6
So I read in the array, and I split it to two arrays created in two structs, for writhing into the pipe. After that I call the divitimp function , a little explanation for the form:
(in my code) divitimp(readwhilegoingdown(lefeleolvas),writewhilegoingdown(lefeleir),readwhilecomingup(felfeleolvas),writewhilecomingup(felfeleir))
After the divitimp function started I use fork, If it works(no errors) I look if it is the child or the parent process(the code is the same in the if and in the else), after that (in the if ) I read out one struct from the pipe if the array in the struct is not longer than two element I write the sorted struct to the writewhilecomingup pipe and not calling back the divitimp function, if the array is longer than 2, I split the array to two arrays created in two structs and i write them to writewhilegoingdown pipe and calling back the divitimp function.
After these I want to wait until the child process end and I use merge sort to sort the sorted arrays and then I write the results(eredmeny) in to the writewhilecomingup pipe.
After the divitimp function finished i go back to main and read the solution struct from the readwhilegoingup pipe, and write it to the output.dat.
The problem is the processes (parent and child) end in a random order.
Source code (very long sorry, but without the code I can't explain the problem):
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
typedef struct{
int n;
int a[100];
}TOMB;
void divitimp(int lefeleolvas, int lefeleir,int felfeleolvas,int felfeleir){
pid_t pid;
int i;
if ((pid = fork()) < 0){
perror("fork hiba");
}
else{
printf("pid= %i \n",pid);
if(pid==0){
TOMB valtozo;
read(lefeleolvas,& valtozo, sizeof(valtozo));
if(valtozo.n>2){
TOMB sv,sv1;
sv.n=valtozo.n/2;
sv1.n=valtozo.n-valtozo.n/2;
printf("Uj ismetles:%d ",sv.n);
for(i=0;i<sv.n;i++){
sv.a[i]=valtozo.a[i];
printf(" %d ",sv.a[i]);
}
int ai=sv1.n-1;
printf(" *%d* ", sv1.n);
for(i=0;i<sv1.n;i++){
sv1.a[i]=valtozo.a[ai];
ai++;
printf(" %d ",sv1.a[i]);
}
printf("itt a vege\n");
write(lefeleir,& sv,sizeof(sv));
write(lefeleir,& sv1,sizeof(sv1));
divitimp(lefeleolvas, lefeleir, felfeleolvas, felfeleir);
}
else{
if(valtozo.n==1){
write(felfeleir,& valtozo,sizeof(valtozo));
}
else{
if(valtozo.n==2);{
if(valtozo.a[0]<valtozo.a[1]){
write(felfeleir,& valtozo,sizeof(valtozo));
}
else{
int csere=valtozo.a[1];
valtozo.a[1]=valtozo.a[0];
valtozo.a[0]=csere;
write(felfeleir,& valtozo,sizeof(valtozo));
}
}
}
}
}
else{
TOMB valtozo;
read(lefeleolvas,& valtozo, sizeof(valtozo));
if(valtozo.n>2){
TOMB sv,sv1;
sv.n=valtozo.n/2;
sv1.n=valtozo.n-valtozo.n/2;
printf("Uj ismetles:%d ",sv.n);
for(i=0;i<sv.n;i++){
sv.a[i]=valtozo.a[i];
printf(" %d ",sv.a[i]);
}
int ai=sv1.n-1;
printf(" *%d* ", sv1.n);
for(i=0;i<sv1.n;i++){
sv1.a[i]=valtozo.a[ai];
ai++;
printf(" %d ",sv1.a[i]);
}
printf("itt a vege\n");
write(lefeleir,& sv,sizeof(sv));
write(lefeleir,& sv1,sizeof(sv1));
divitimp(lefeleolvas, lefeleir, felfeleolvas, felfeleir);
exit(0);
}
else{
if(valtozo.n==1){
write(felfeleir,& valtozo,sizeof(valtozo));
exit(0);
}
else{
if(valtozo.n==2);{
if(valtozo.a[0]<valtozo.a[1]){
write(felfeleir,& valtozo,sizeof(valtozo));
exit(0);
}
else{
int csere=valtozo.a[1];
valtozo.a[1]=valtozo.a[0];
valtozo.a[0]=csere;
write(felfeleir,& valtozo,sizeof(valtozo));
exit(0);
}
}
}
}
}
while(wait(NULL)>0);
if(pid==0){
TOMB sv,sv1,eredmeny;
read(felfeleolvas,& sv,sizeof(sv));
read(felfeleolvas,& sv1,sizeof(sv));
int svi=0,sv1i=0;
eredmeny.n=sv.n+sv1.n;
for(i=0;i<sv.n+sv1.n;i++){
if(svi<sv.n&&sv1i<sv1.n){
if(sv.a[svi]<sv1.a[sv1i]){
eredmeny.a[i]=sv.a[svi];
svi++;
}
else{
eredmeny.a[i]=sv1.a[sv1i];
sv1i++;
}
}
else{
if(svi<sv.n){
eredmeny.a[i]=sv.a[svi];
svi++;
}
else{
eredmeny.a[i]=sv1.a[sv1i];
sv1i++;
}
}
printf("e=%d sv=%d sv1=%d\n",eredmeny.a[i],sv.a[svi-1],sv1.a[sv1i-1]);
}
write(felfeleir,& eredmeny, sizeof(eredmeny));
}
}
}
int main(){
FILE *f= fopen("input.dat","r");
if(!f){
perror("nincs megfelelo allomany");
exit(1);
}
FILE *g= fopen("output.dat","w");
int n;
fscanf(f,"%d",&n);
int a[n];
a[0]=n;
int i=0;
printf("%d",n);
for(i;i<n;i++){
fscanf(f,"%d",&a[i]);
}
//printf("%d \n",n);
TOMB betesz1, betesz2;
betesz1.n=n/2;
for(i=0;i<betesz1.n;i++){
betesz1.a[i]=a[i];
printf("%d\n ",a[i]);
}
betesz2.n=n-n/2;
int ai=betesz2.n;
for(i=0;i<betesz2.n;i++){
betesz2.a[i]=a[ai];
ai++;
printf("%d\n ",a[ai-1]);
}
int pfd[2];
if (pipe(pfd) < 0){
perror("pipe hiba");
}
int pfd1[2];
if (pipe(pfd1) < 0){
perror("pipe hiba");
}
write(pfd[1],& betesz1, sizeof(betesz1));
write(pfd[1],& betesz2, sizeof(betesz2));
divitimp(pfd[0],pfd[1],pfd1[0],pfd1[1]);
TOMB eredmeny;
read(pfd1[0],& eredmeny,sizeof(eredmeny));
printf("%d\n",eredmeny.n);
for(i=0;i<eredmeny.n;i++){
fprintf(g,"%d ",eredmeny.a[i]);
}
fclose(f);
fclose(g);
return 0;
}