SUBROUTINE lpm_extend_particle_array( number_of_new_particles )

!------------------------------------------------------------------------------!
! Current revisions:
! ------------------
! 
!
! Former revisions:
! -----------------
! $Id: lpm_extend_particle_array.f90 850 2012-03-15 12:09:25Z gryschka $
!
! 849 2012-03-15 10:35:09Z raasch
! initial revision (former part of advec_particles)
!
!
! Description:
! ------------
! Allocates more memory for the particle array.
!------------------------------------------------------------------------------!

    USE particle_attributes

    IMPLICIT NONE

    INTEGER ::  new_maximum_number, number_of_new_particles

    LOGICAL, DIMENSION(:), ALLOCATABLE ::  tmp_particle_mask

    TYPE(particle_type), DIMENSION(:), ALLOCATABLE ::  tmp_particles



    new_maximum_number = maximum_number_of_particles + &
                   MAX( 5*number_of_new_particles, number_of_initial_particles )

    IF ( write_particle_statistics )  THEN
       CALL check_open( 80 )
       WRITE ( 80, '(''*** Request: '', I7, '' new_maximum_number(prt)'')' ) &
                            new_maximum_number
       CALL close_file( 80 )
    ENDIF

    ALLOCATE( tmp_particles(maximum_number_of_particles), &
              tmp_particle_mask(maximum_number_of_particles) )

    tmp_particles     = particles
    tmp_particle_mask = particle_mask

    DEALLOCATE( particles, particle_mask )
    ALLOCATE( particles(new_maximum_number), particle_mask(new_maximum_number) )

    maximum_number_of_particles = new_maximum_number

    particles(1:number_of_particles) = tmp_particles(1:number_of_particles)
    particle_mask(1:number_of_particles) = &
                                       tmp_particle_mask(1:number_of_particles)
    particle_mask(number_of_particles+1:maximum_number_of_particles) = .TRUE.

    DEALLOCATE( tmp_particles, tmp_particle_mask )


 END SUBROUTINE lpm_extend_particle_array