forrtl: severe (151): allocatable array is already allocated- - fortran

Question

/var/spool/torque/mom_priv/jobs/775.head.cluster.SC: line 22: 28084 Segmentation fault ./a.out
I am new in Fortran and this is the first time I work with HPC and OpenMP.
In my code, I have a loop that should be parallel. I use some dynamic variables that all of them are dummy in the parallel loop.
I allocate the dynamic variables in parallel loop
!$OMP PARALLEL DO
do 250 iconf = 1,config
allocate(randx(num),randy(num),randz(num),unit_cg(num), &
& x(nfftdim1),y(nfftdim2),z(nfftdim3),fr1(num), &
& fr2(num),fr3(num),theta1(order,num), &
& theta2(order,num),theta3(order,num), &
& Q(nfftdim1,nfftdim2,nfftdim3))
... call some subroutines and do calculations ...
deallocate(randx,randy,randz,unit_cg,fr1,fr2,fr3,theta1,theta2, &
& theta3,x,y,z,Q)
250 continue
!$OMP END PARALLEL DO
I omited some irrelevant part of code. When the program is executed, this error occurs:
forrtl: severe (151): allocatable array is already allocated
I allocated the variables outside the parallel region, it works for small data, but for large data this error occurs:
/var/spool/torque/mom_priv/jobs/775.head.cluster.SC: line 22: 28084 Segmentation fault ./a.out
I used PRIVATE clause for dynamic variables (dummy variables):
!$OMP PARALLEL DO DEFAULT(SHARED) PRIVATE(randx,randy,randz, &
!$OMP& unit_cg,fr1,fr2,fr3,theta1,theta2,theta3,x,y,z,Q, &
!$OMP& dir_ene,rec_ene,corr_ene,energy_final,plproduct_avg, &
!$OMP& correlation_term)
and allocated variables inside parallel loop, but the same error,
at last I changed the code to:
allocate(randx(num),randy(num),randz(num),unit_cg(num), &
& x(nfftdim1),y(nfftdim2),z(nfftdim3),fr1(num), &
& fr2(num),fr3(num),theta1(order,num), &
& theta2(order,num),theta3(order,num), &
& Q(nfftdim1,nfftdim2,nfftdim3))
!$OMP PARALLEL DO DEFAULT(SHARED) PRIVATE(randx,randy,randz, &
!$OMP& unit_cg,fr1,fr2,fr3,theta1,theta2,theta3,x,y,z,Q, &
!$OMP& dir_ene,rec_ene,corr_ene,energy_final,plproduct_avg, &
!$OMP& correlation_term)
do 250 iconf = 1,config
... call some subroutines and do calculations ...
250 continue
!$OMP END PARALLEL DO
deallocate(randx,randy,randz,unit_cg,fr1,fr2,fr3,theta1,theta2, &
& theta3,x,y,z,Q)
it fails at run-time. it starts N (number of thread) loops, but can not complete them, and again this error:
/var/spool/torque/mom_priv/jobs/775.head.cluster.SC: line 22: 28084 Segmentation fault ./a.out
any idea?

Answer 1

I changed the code and finally it WORKS!
The directive !$OMP PARALLEL DO is the shortcut of two directives !$OMP PARALLEL and !$OMP DO. I used these two directives (instead of !$OMP PARALLEL DO) and put allocation inside parallel region. I guess (but I'm not sure), now the compiler knows how to get memories for private variables, because I put private clause before allocation and so the segmentation fault dose not occur.
!$OMP PARALLEL DEFAULT(SHARED) PRIVATE(iconf,d,randx, &
!$OMP& randy,randz,unit_cg,theta1,theta2,theta3,fr1,fr2,fr3,Q, &
!$OMP& plproduct_avg)
allocate(randx(num),randy(num),randz(num),unit_cg(num), &
& fr1(num),fr2(num),fr3(num),theta1(order,num), &
& theta2(order,num),theta3(order,num), &
& Q(nfftdim1,nfftdim2,nfftdim3))
!$OMP DO
do 250 iconf = 1,config
... call some subroutines and do calculations ...
250 continue
!$OMP END DO
deallocate(randx,randy,randz,unit_cg,fr1,fr2,fr3,theta1,theta2, &
& theta3,Q)
!$OMP END PARALLEL