program main !*****************************************************************************80 ! !! brownian_motion_simulation_test() tests brownian_motion_simulation(). ! ! Licensing: ! ! This code is distributed under the MIT license. ! ! Modified: ! ! 03 September 2021 ! ! Author: ! ! John Burkardt ! implicit none integer, parameter :: rk = kind ( 1.0D+00 ) real ( kind = rk ) d real ( kind = rk ), allocatable :: dsq(:,:) character ( len = 255 ) header integer k integer m integer n real ( kind = rk ) t real ( kind = rk ), allocatable :: x(:,:) call timestamp ( ) write ( *, '(a)' ) '' write ( *, '(a)' ) 'brownian_motion_simulation_test():' write ( *, '(a)' ) ' FORTRAN90 version' write ( *, '(a)' ) ' Test brownian_motion_simulation().' ! ! Compute the path of a particle undergoing Brownian motion. ! do m = 1, 2 n = 1001 d = 10.0D+00 t = 1.0D+00 allocate ( x(1:m,1:n) ) call brownian_motion_simulation ( m, n, d, t, x ) if ( m == 1 ) then header = 'motion_1d' else if ( m == 2 ) then header = 'motion_2d' end if call brownian_motion_display ( m, n, x, header ) deallocate ( x ) end do ! ! Estimate the average displacement of the particle from the origin ! as a function of time. ! do m = 1, 3 k = 40 n = 1001 d = 10.0D+00 t = 1.0D+00 allocate ( dsq(1:k,1:n) ) call brownian_displacement_simulation ( k, n, m, d, t, dsq ) if ( m == 1 ) then header = 'displacement_1d' else if ( m == 2 ) then header = 'displacement_2d' else if ( m == 3 ) then header = 'displacement_3d' end if call brownian_displacement_display ( k, n, m, d, t, dsq, header ) deallocate ( dsq ) end do ! ! Terminate. ! write ( *, '(a)' ) '' write ( *, '(a)' ) 'brownian_motion_simulation_test():' write ( *, '(a)' ) ' Normal end of execution.' write ( *, '(a)' ) '' call timestamp ( ); stop 0 end