from visual import *
from random import *
from math import *

##lattice length
L=10
# create a list 
spin=[]

for i in range(0,L):
# add a new list for each element of original list
# allows us to create a 2D lattice or array of spins 
    spin.append([])
    for j in range(0,L):
# i and j now give lattice coordinates of spin object
        spin[i].append(sphere(pos=vector(i-L/2,j-L/2,0),
                              radius=0.2,color=color.red,state=1))

        
## set ratio of energy to thermal energy kT
T=3.0
MAXITS=1000

## code for loop over T goes in here

## remember to indent all following code after adding the T loop.
for its in range(0,MAXITS):

# simulation code to update configuration of spins using Monte Carlo
# algorithm

    for i in range (0,L):
        for j in range (0,L):
            rate(200)
#using periodic boundary conditions in 2D
            deltaE=(2.0/T)*spin[i][j].state*(
                                  spin[i][(j+1)%L].state+
                                  spin[i][(j-1+L)%L].state+
                                  spin[(i+1)%L][j].state+
                                  spin[(i+L-1)%L][j].state
                                            )
            if (exp(-deltaE)>random()):
                spin[i][j].state=-spin[i][j].state
                
            if (spin[i][j].state==1):
                spin[i][j].color=color.red
            else:
                spin[i][j].color=color.blue
#  end simulation part of code