Program drunkards_walk
!------------------------------------------------------------------------------
!Program: Drunkard's Walk
!Author: Chris Harper
!Date: 3/6/2008
!------------------------------------------------------------------------------

IMPLICIT NONE

!declarations
integer :: i, j
integer :: pos, home_count, pub_count, rolls
real :: roll_avg, random(SIZE)
integer :: time_array(8), seed(1)

!initialize the random number generator
call date_and_time(values = time_array)
seed(1) = time_array(8)
call random_seed(put =, SIZE

!output a header
print *, "Drunkard's Walk"
print "(A9, T12, A10, T24, A5, T30, A6)", &
  "Start Pos", "Avg Blocks", "% Pub", "% Home"do i = 2, 7 !starting point
	home_count = 0
	pub_count = 0
	roll_avg = 0
	do j = 1, 500 !500 tests per starting point
		rolls = 0
		pos = i
		do
			rolls = rolls + 1
			
			call random_number(random)
			if (random < (2.0/3.0)) then
				pos = pos - 1
			else
				pos = pos + 1
			end if
			
			if (pos == 8) then
				home_count = home_count + 1
				exit
			else if (pos == 1) then
				pub_count = pub_count + 1
				exit
			end if
			
			if (rolls > 1000) exit !iteration cap
		end do
		
		!Current_Avg = ((Prev_Avg * Prev_Count) + New_Value) / New_Count
		roll_avg = ((roll_avg * (j-1)) + rolls) / j
	end do
	
	print "(I9, T12, F10.4, T24, F5.1, T31, F5.1)", i, roll_avg, &
	  ((pub_count/500.0)*100), ((home_count/500.0)*100)
end do


end