Nesting OMP DO directives - Fortran - fortran

Question

I'm having problems trying to nest a OMP DO directive inside another OMP DO directive in Fortran.
Here's the following code:
DO in=2,n_niveles
allocate(cvalor(2,npuntosp(in),npuntost(in)))
!allocate(avalor(2,npuntosp(in-1),npuntost(in-1)))
allocate(valor_t2(npuntost(in),npuntosp(in-1),2))
!$OMP PARALLEL NUM_THREADS(hilos) DEFAULT(PRIVATE) FIRSTPRIVATE(n_niveles,in) SHARED(npuntosp,npuntost,cubos,central_reg,sumazm1n,expo,mphi,mtheta)
!$OMP DO SCHEDULE(STATIC)
DO aux=1,cubos(in-1)%ncubos_nivel
...
(some code here)
...
!$OMP PARALLEL NUM_THREADS(hilos) DEFAULT(PRIVATE) FIRSTPRIVATE(cuboj,in) SHARED(valor_t2,cvalor)
!$OMP DO SCHEDULE(STATIC)
do i=1,npuntost(in)
val=mtheta(in-1)%inicio(i,1)
do jj=val,val+mtheta(in-1)%inicio(i,2)
do k=1,npuntosp(in-1)
valor_t2(i,k,1)=valor_t2(i,k,1)+mtheta(in-1)%matriz(i,jj)*sumazm1n(in-1)%region(cuboj)%valor(1,k,jj)
valor_t2(i,k,2)=valor_t2(i,k,2)+mtheta(in-1)%matriz(i,jj)*sumazm1n(in-1)%region(cuboj)%valor(2,k,jj)
end do
end do
do k=1,npuntosp(in)
val=mphi(in-1)%inicio(k,1)
do jj=val,val+mphi(in-1)%inicio(k,2)
cvalor(1,k,i)=cvalor(1,k,i)+valor_t2(i,jj,1)*mphi(in-1)%matriz(jj,k)
cvalor(2,k,i)=cvalor(2,k,i)+valor_t2(i,jj,2)*mphi(in-1)%matriz(jj,k)
end do
end do
end do
!$OMP END DO
!$OMP END PARALLEL
...
(some code here)
...
END DO
!$OMP END DO
!$OMP END PARALLEL
deallocate(cvalor)
deallocate(valor_t2)
END DO
When the code is executed, an access violation exception occurs inside the second OpenMP parallel region. Sometimes that exception is changed for an overflow at the variable valor_t2.
Maybe OpenMP does not support this kind of parallelization, but I've searched over the net and didn't found anything about. I know that OpenMP supports the use of various OMP PARALLEL directives nested one inside another and I know how it works. But I'm having a headache with this problem.
Any ideas about what it's happening?
Thank you so much!

Answer 1

You're going to want to use the collapse clause in the do loop at the top level. See the link below for information:
https://computing.llnl.gov/tutorials/openMP/
As long as the code represented by (some code here) doesn't contain any loops, this should work.