cours-m1-eea/455-Codage_Sources/algo_code/code_arithmetique.py

#!/usr/bin/env python3

import numpy as np

N=10
p = 0.2
P = np.random.rand(N)
X = np.zeros(N,dtype='int')
for i in range(N):
    if P[i] > p:
        X[i] = 1

X=[0,1,0,0,1,0,0,0,0,0]
print(X)

def binary(n,m,b=2):
    """
    Convertie un nombre décimal en sa version binaire tronqué à m bits.
    """
    binaire= np.floor(n*b**m) # on se décale dans les entiers et on floor

    return binaire,np.binary_repr(int(binaire))

def arithm(X,p):
    l=[0]
    h= [1]
    for x in X:
        if x == 0:
            h.append(l[-1]+p*(h[-1]-l[-1]))
            l.append(l[-1])
        else:
            l.append(l[-1]+p*(h[-1]-l[-1]))
            h.append(h[-1])

            lmb = (l[-1]+h[-1])/2

            mu = int(-np.log2(h[-1]-l[-1]))+1
    code = binary(lmb,mu)
    return code,lmb,mu

def arithm_pratique(X,p):
    l = [0]                     # borne inférieur
    h =[1]                      # borne supérieur
    f = 0                       # follow
    c =[]                       # code
    for k in range(len(X)):
        print("for loop")
        if X[k] == 0:
            l.append(l[-1])
            h.append(l[-1]+p*(h[-1]-l[-1]))
        else:
           l.append(l[-1]+p*(h[-1]-l[-1]))
           h.append(h[-1])
        print(X[k])
        print(l[-3:])
        print(h[-3:])
        while ((l[-1]>=0 and h[-1]<0.5)
            or (l[-1]>=0.5 and h[-1]<1)
            or (l[-1]>= 0.25 and h[-1]<0.75)):
            print(" loop")
            if (l[-1]>=0 and h[-1]<0.5):
                print("  case 1")
                c += [0]+[1]*f
                l[-1] *=2
                h[-1] *=2
            elif (l[-1]>=0.5 and h[-1]<1):
                print("  case 2")
                c += [1]+[0]*f
                l[-1] = 2*l[-1]-1
                h[-1] = 2*h[-1]-1
            elif (l[-1]>= 0.25 and h[-1]<0.75):
                print("  case 3")
                f +=1
                l[-1] = 2*l[-1]-0.5
                h[-1] = 2*h[-1]-0.5
    return c

#print(arithm(X,p))
print(arithm_pratique(X,p))