Specific thread order in C using GCC and OMP - c++

Question

I need to make 4 teams with 4 threads each one with contiguous processors.
The result I'm expecting is, for example:
Team 0 Thread 0 Processor: 0
Team 0 Thread 1 Processor: 1
Team 0 Thread 2 Processor: 2
Team 0 Thread 3 Processor: 3
Team 1 Thread 0 Processor: 4
Team 1 Thread 1 Processor: 5
Team 1 Thread 2 Processor: 6
Team 1 Thread 3 Processor: 7
Team 2 Thread 0 Processor: 8
Team 2 Thread 1 Processor: 9
Team 2 Thread 2 Processor: 10
Team 2 Thread 3 Processor: 11
Team 3 Thread 0 Processor: 12
Team 3 Thread 1 Processor: 13
Team 3 Thread 2 Processor: 14
Team 3 Thread 3 Processor: 15
I can handle Processor Affinity in GCC using the GOMP_CPU_AFFINITY variable.
I'm using:
#pragma omp parallel num_threads(4)
twice in order to get 2 fork levels.
At the moment I'm having this order in GOMP_CPU_AFFINITY:
0 4 8 12 1 2 3 5 6 7 9 10 11 13 14 15
So the first fork, the "fathers fork", gets:
Team 0 Thread 0 Processor: 0
Team 1 Thread 0 Processor: 4
Team 2 Thread 0 Processor: 8
Team 3 Thread 0 Processor: 12
The problem I'm having is that the second group of forks make without any order so, for example I could have this situation (I'm using #pragma omp atomic so only one 'father' can ask for more processors at any time):
Team 0 Thread 0 Processor: 0
Team 0 Thread 1 Processor: 5
Team 0 Thread 2 Processor: 6
Team 0 Thread 3 Processor: 7
Team 1 Thread 0 Processor: 4
Team 1 Thread 1 Processor: 13
Team 1 Thread 2 Processor: 14
Team 1 Thread 3 Processor: 15
Team 2 Thread 0 Processor: 8
Team 2 Thread 1 Processor: 1
Team 2 Thread 2 Processor: 2
Team 2 Thread 3 Processor: 3
Team 3 Thread 0 Processor: 12
Team 3 Thread 1 Processor: 9
Team 3 Thread 2 Processor: 10
Team 3 Thread 3 Processor: 11
The question is: Is there any way to make this second petition in order?
I think I would have to make some sinchronization method with locks or something...
Thanks in advance!
Javier

Answer 1

Finally I could make this works, this is my code:
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <sched.h>
int main(int argc, char *argv[]){
int padre, hijo;
int contador = 0;
omp_set_nested(1);
int suma;
#pragma omp parallel private(padre) shared(contador) num_threads(4)
{
padre = omp_get_thread_num();
{
while(contador != padre){
// Don't know what to put here
};
#pragma omp parallel private(hijo) shared(padre, contador) num_threads(4)
{
hijo = omp_get_thread_num();
printf("\nFather: %d Son: %d Processor: %d\n", padre, hijo, sched_getcpu());
#pragma omp master
{
contador++;
}
}
}
}
}
Note: Padre is Father, Hijo is Son and Contador is Counter in Spanish :P
The problem I'm facing now is that if I compile my code with -O3 optimizations, the while loop 'dissapear' unless I put, for example, a printf line inside the loop. I think I should ask it in another question!
Thanks to you all!
Javier