program bruteforce

	use mpi
	implicit none
	integer :: n,m,noprime,total,nmin,nmax
	integer ::  rank, nb_mpi_processes, ierror, hostname_len

	call MPI_INIT(ierror) ! Init MPI (init MPI_COMM_WORLD communicator, set rank to each process, etc)
	call MPI_COMM_SIZE(MPI_COMM_WORLD, nb_mpi_processes, ierror) ! Ask the number of MPI processes running
	call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierror) ! Ask the rank of the current process

	total=0
	nmin=(20000000/nb_mpi_processes)*rank+1
	nmax=(20000000/nb_mpi_processes)*(rank+1)
	print *,'rank',rank,nmin,nmax

	do n=nmin,nmax

		if(modulo(n,2) == 0) then; noprime = 1
		elseif(modulo(n,3) == 0) then; noprime = 1
		else
			do m=4,int(sqrt(real(n)))
				if(modulo(n,m) == 0) then
					noprime = 1
					exit
				end if
			end do
		end if
		if(noprime == 1) then
			noprime = 0
		else
		total = total + 1
	end if

	end do

	print *, rank,'Found ', total, ' prime numbers'

	call MPI_FINALIZE ( ierror ) ! Close MPI

end program bruteforce