我正在尝试增加以下Fortran自行避免随机游走程序中的可能步骤数。
增加步数可以使方形平均距离更准确
我会提供您的解决方案和建议。
PROGRAM Two_dimensional_Self_Avoiding__Random_Walks
implicit none
integer, dimension(:,:), allocatable :: lattice
integer, dimension(1:46):: na
integer :: i,x,y,xt,yt,id,step,xx, ns,n,ii,III,choice
real :: r,dis,dis2,square,d,d2
Logical :: terminate,newsite
CALL RANDOM_SEED()
! intial values for end to end distance
read(*,*) choice
if (choice == 1) then
print*, ' Enter ns and n '
read(*,*) ns
na = (/(III, III=5, 50, 1)/)
do ii= 1, 46
dis = 0.0; dis2 = 0.0
n = na(ii)
allocate(lattice(-n:n,-n:n))
CALL walks() ! self avoiding walks
IF (ALLOCATED (lattice)) DEALLOCATE (lattice)
enddo
elseif (choice == 2) then
print*, ' Enter ns and n '
read(*,*) ns , n
dis = 0.0; dis2 = 0.0
allocate(lattice(-n:n,-n:n))
CALL walks()
endif
CONTAINS
SUBROUTINE walks
DO i = 1,ns
lattice = 0; x = 0; y = 0
step = 0; terminate = .FALSE.
DO WHILE ((.NOT. terminate) .AND. (step <= n))
xt = x; yt = y
xx = lattice(x+1,y)+lattice(x-1,y) &
+lattice(x,y+1)+lattice(x,y-1)
IF (xx == 4) THEN
terminate = .TRUE.
ELSE
newsite = .FALSE.
DO WHILE (.NOT. newsite)
CALL RANDOM_NUMBER(r)
id = INT(r*4.0)
IF (id == 0) THEN
x = xt + 1; y = yt
ELSEIF (id == 1) THEN
x = xt - 1; y = yt
ELSEIF (id == 2) THEN
x = xt; y = yt + 1
ELSEIF (id == 3) THEN
x = xt; y = yt - 1
ENDIF
IF (lattice(x,y) == 0) newsite = .TRUE.
ENDDO
step = step + 1; lattice(x,y) = 1
ENDIF
write(7,*) x,y
ENDDO
write(10,*),step
square = float(x**2+y**2)
dis = dis + sqrt(square); dis2 = dis2 + square
d = dis/ns; d2=dis2/ns
ENDDO
write(11,*), ns,n, d, d2
print*, ns,n, d, d2
END SUBROUTINE walks
END PROGRAM Two_dimensional_Self_Avoiding__Random_Walks