MPI_ALLGATHER error parallelizing code - fortran

Question

I'm trying to parallelize the following code.
subroutine log_likelihood(y, theta, lli, ll)
doubleprecision, allocatable, intent(in) :: y(:)
doubleprecision, intent(in) :: theta(2)
doubleprecision, allocatable, intent(out) :: lli(:)
doubleprecision, intent(out) :: ll
integer :: i
ALLOCATE (lli(size(y)))
lli = 0.0d0
ll = 0.0d0
do i = 1, size(y)
lli(i) = -log(sqrt(theta(2))) - 0.5*log(2.0d0*pi) &
- (1.0d0/(2.0d0*theta(2)))*((y(i)-theta(1))**2)
end do
ll = sum(lli)
end subroutine log_likelihood
To do this, I'm trying to use MPI_ALLGATHER. This is the code I wrote
subroutine log_likelihood(y, theta, lli, ll)
doubleprecision, allocatable, intent(in) :: y(:)
doubleprecision, intent(in) :: theta(2)
doubleprecision, allocatable, intent(out) :: lli(:)
doubleprecision, intent(out) :: ll
integer :: i, size_y, diff
size_y=size(y)
ALLOCATE (lli(size_y))
!Broadcasting
call MPI_BCAST(theta, 1, MPI_DOUBLE_PRECISION, 0, MPI_COMM_WORLD, ierr)
call MPI_BCAST(y, 1, MPI_DOUBLE_PRECISION, 0, MPI_COMM_WORLD, ierr)
! Determine how many points to handle with each proc
points_per_proc = (size_y + numprocs - 1)/numprocs
! Determine start and end index for this proc's points
istart = proc_num * points_per_proc + 1
iend = min((proc_num + 1)*points_per_proc, size_y)
diff = iend-istart+1
allocate(proc_contrib(istart:iend))
do i = istart, iend
proc_contrib(i) = -log(sqrt(theta(2))) - 0.5*log(2.0d0*pi) &
- (1.0d0/(2.0d0*theta(2)))*((y(i)-theta(1))**2)
end do
call MPI_ALLGATHER(proc_contrib, diff, MPI_DOUBLE_PRECISION, &
lli, diff, MPI_DOUBLE_PRECISION, &
MPI_COMM_WORLD, ierr)
ll = sum(lli)
end subroutine log_likelihood
When I try to run my program, I get the following error.
$ mpiexec -n 2 ./mle.X
Fatal error in PMPI_Allgather: Internal MPI error!, error stack:
PMPI_Allgather(961)......: MPI_Allgather(sbuf=0x7ff2f251b860, scount=1500000, MPI_DOUBLE_PRECISION, rbuf=0x7ff2f2ad5650, rcount=3000000, MPI_DOUBLE_PRECISION, MPI_COMM_WORLD) failed
MPIR_Allgather_impl(807).:
MPIR_Allgather(766)......:
MPIR_Allgather_intra(560):
MPIR_Localcopy(357)......: memcpy arguments alias each other, dst=0x7ff2f2ad5650 src=0x7ff2f251b860 len=12000000
===================================================================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= EXIT CODE: 1
= CLEANING UP REMAINING PROCESSES
= YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================
Can somebody please explain to me what I'm doing wrong?
Thanks!

Answer 1

I finally was able to solve my problem. The serial and parallel versions of my code are available at https://bitbucket.org/ignacio82/bhhh
subroutine log_likelihood(y, n, theta, lli, ll)
integer, intent(in) :: n
doubleprecision, intent(in) :: y(n)
doubleprecision, intent(in) :: theta(2)
doubleprecision, intent(out) :: lli(n)
doubleprecision, intent(out) :: ll
integer :: i
do i = istart, iend
proc_contrib(i-istart+1) = -log(sqrt(theta(2))) - 0.5*log(2.0d0*pi) &
- (1.0d0/(2.0d0*theta(2)))*((y(i)-theta(1))**2)
end do
if ( mod(n,numprocs)==0 ) then
call MPI_ALLGATHER(proc_contrib, points_per_proc, MPI_DOUBLE_PRECISION, &
lli, points_per_proc, MPI_DOUBLE_PRECISION, &
MPI_COMM_WORLD, ierr)
else if (numprocs-1 == proc_num ) then
recvcounts(numprocs) = iend-istart+1
call MPI_ALLGATHERV(proc_contrib, points_per_proc, MPI_DOUBLE_PRECISION, &
lli, recvcounts, displs, MPI_DOUBLE_PRECISION, &
MPI_COMM_WORLD, ierr)
end if
ll = sum(lli)
end subroutine log_likelihood