Thermo ising.py

From Werner KRAUTH

import math, os 

L = 6
N = L * L
filename = 'data_dos_L%i.txt' % L
if os.path.isfile(filename):
    dos = {}
    f = open(filename, 'r')
    for line in f:
        E, N_E = line.split()
        dos[int(E)] = int(N_E)
    f.close()
else:
   exit('input file missing')
list_T = [0.5 + 0.5 * i for i in range(10)]
for T in list_T:
    Z = 0.0
    E_av = 0.0
    M_av = 0.0
    E2_av = 0.0
    for E in dos.keys():
        weight = math.exp(- E / T) * dos[E]
        Z += weight
        E_av += weight * E
        E2_av += weight * E ** 2
    E2_av /= Z
    E_av /= Z
    cv = (E2_av - E_av ** 2) / N / T ** 2
    print T, E_av / float(N), cv