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FORK JOIN

Fork Join:

Fork/join blocks provide the primary mechanism for creating concurrent processes.The all | any | none options specify when the code after the fork/join block executes.The default is all.

all :: The default is all. Code after the block executes after all of the concurrent processes are completed.
any :: When any is used, code after the block executes after any single concurrent process is completed.
none :: When none is used, code after the block executes immediately, without waiting for any of the processes to complete.

EXAMPLE : fork/join none

program main {
delay(10);

printf(" BEFORE fork time = %d \n",get_time(LO) );
fork {
delay (20);
printf("time = %d delay 20 \n ",get_time(LO) );
}
{
delay(10);
printf("time = %d delay 10 \n ",get_time(LO) );
}
{
delay(5);
printf("time = %d delay 5 \n ",get_time(LO) );
}
join none
printf(" time = %d Outside the main fork \n",get_time(LO) );
delay(40);
}
RESULTS

BEFORE fork time = 10
time = 10 Outside the main fork
time = 15 delay 5
time = 20 delay 10
time = 30 delay 20

EXAMPLE : fork/join any

program main {

delay(10);

printf(" BEFORE fork time = %d \n",get_time(LO) );
fork {
delay (20);
printf("time = %d delay 20 \n ",get_time(LO) );
}
{
delay(10);
printf("time = %d delay 10 \n ",get_time(LO) );
}
{
delay(5);
printf("time = %d delay 5 \n ",get_time(LO) );
}
join any
printf(" time = %d Outside the main fork \n",get_time(LO) );
delay(40);
}
RESULTS

BEFORE fork time = 10
time = 15 delay 5
time = 15 Outside the main fork
time = 20 delay 10
time = 30 delay 20

EXAMPLE : fork/join all

program main {

delay(10);

printf(" BEFORE fork time = %d \n",get_time(LO) );
fork {
delay (20);
printf("time = %d delay 20 \n ",get_time(LO) );
}
{
delay(10);
printf("time = %d delay 10 \n ",get_time(LO) );
}
{
delay(5);
printf("time = %d delay 5 \n ",get_time(LO) );
}
join all
printf(" time = %d Outside the main fork \n",get_time(LO) );
delay(40);
}

RESULTS

BEFORE fork time = 10
time = 15 delay 5
time = 20 delay 10
time = 30 delay 20
time = 30 Outside the main fork

When defining a fork/join block, encapsulating the entire fork inside braces ({}) results in the entire block being treated as a single thread, and the code executes consecutively.

EXAMPLE : sequential statement in fork/join

program main {
delay(10);

printf(" First fork time = %d \n",get_time(LO) );
fork {
delay (20);
printf("time = %d delay 20 \n ",get_time(LO),i);
}
{
delay(10);
printf("time = %d delay 10 \n ",get_time(LO),j);
}
{
delay(5);
printf("time = %d delay 5 \n ",get_time(LO),m);
delay(2);
printf("time = %d delay 2 \n ",get_time(LO),m);

}
join any
printf(" time = %d Outside the main fork \n",get_time(LO) );

delay(40);
}

RESULTS

First fork time = 10
time = 15 delay 5
time = 17 delay 2
time = 17 Outside the main fork
time = 20 delay 10
time = 30 delay 20

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