diff --git a/.gitignore b/.gitignore
index ba0430d2..979f738d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-__pycache__/
\ No newline at end of file
+__pycache__/
+*.png
\ No newline at end of file
diff --git a/velo_rent.py b/velo_rent.py
index d06d3be6..364a779c 100644
--- a/velo_rent.py
+++ b/velo_rent.py
@@ -1,52 +1,98 @@
-# download modsim.py if necessary
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 
-from os.path import basename, exists
+from multiprocessing import Pool
 
-def download(url):
-    filename = basename(url)
-    if not exists(filename):
-        from urllib.request import urlretrieve
-        local, _ = urlretrieve(url, filename)
-        print('Downloaded ' + local)
-    
-download('https://github.com/AllenDowney/ModSimPy/raw/master/modsim.py')
+import matplotlib.pyplot as plt
+import numpy as np
+import pandas as pd
 
-# import functions from modsim
 
-from modsim import *
-import matplotlib.pyplot as plt
+def State(**variables):
+    """Contains the values of state variables."""
+    return pd.Series(variables, name="state")
+
+
+def flip(p=0.5):
+    """Flips a coin with the given probability.
+
+    p: float 0-1
+
+    returns: boolean (True or False)
+    """
+    return np.random.random() < p
+
+
+def TimeSeries(*args, **kwargs):
+    """Make a pd.Series object to represent a time series."""
+    if args or kwargs:
+        # underride(kwargs, dtype=float)
+        series = pd.Series(*args, **kwargs)
+    else:
+        series = pd.Series([], dtype=float)
+
+    series.index.name = "Time"
+    if "name" not in kwargs:
+        series.name = "Quantity"
+    return series
+
 
 bikeshare = State(mailly=10, moulin=2)
 
-def velo_a_mailly():
+
+def velo_a_moulin():
     # print('Moving a bike to moulin')
     bikeshare.mailly -= 1
     bikeshare.moulin += 1
 
-def velo_a_moulin():
+
+def velo_a_mailly():
     # print('Moving a bike to mailly')
     bikeshare.moulin -= 1
     bikeshare.mailly += 1
 
+
 def step(p1, p2):
     if flip(p1):
         velo_a_mailly()
-    
+
     if flip(p2):
         velo_a_moulin()
 
-results = TimeSeries()
 
-results[0] = bikeshare.mailly
+def run_simulation(num_steps, p1, p2):
+    results = TimeSeries()
+    results[0] = bikeshare.mailly
+    for i in range(num_steps):
+        step(p1, p2)
+        results[i + 1] = bikeshare.mailly
+    return results
+
+
+def run_simulations_in_parallel(params_list):
+    with Pool(3) as p:
+        result = p.starmap_async(run_simulation, params_list)
+        return result.get()
+
+
+params_list = [(10000, 0.5, 0.47), (10000, 0.5, 0.33), (10000, 0.47, 0.6)]
+res1, res2, res3 = run_simulations_in_parallel(params_list)
+
+
+fig, (ax1, ax2, ax3) = plt.subplots(3, 1)
+ax1.plot(res1)
+ax1.set_title("Velos à Mailly")
+ax1.set_xlabel("Temps")
+ax1.set_ylabel("nombre")
+
+ax2.plot(res2)
+ax2.set_title("Velos à Mailly")
+ax2.set_xlabel("Temps")
+ax2.set_ylabel("nombre")
 
-for i in range(60*14*30):
-    # print(f"step {i}")
-    step(0.5, 0.4)
-    results[i+1] = bikeshare.mailly
+ax3.plot(res3)
+ax3.set_title("Velos à Mailly")
+ax3.set_xlabel("Temps")
+ax3.set_ylabel("nombre")
 
-fig, ax = plt.subplots()
-ax.plot(results)
-ax.set_title("Velos à Mailly")
-ax.set_xlabel("Temps")
-ax.set_ylabel("nombre")
-plt.show()
\ No newline at end of file
+plt.savefig("mailly.png")