minor fixes
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#!/usr/bin/env python3
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# Importing the libraries
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import os
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import wget
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import gzip
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import time
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import warnings
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import scipy as sp
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import numpy as np
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import pandas as pd
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import networkx as nx
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from os.path import exists
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from scipy.sparse import *
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from scipy.sparse.linalg import norm
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import plotly.graph_objs as go
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warnings.simplefilter(action='ignore', category=FutureWarning)
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# some stupid pandas function that doesn't work
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class Utilities:
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# Importing the dataset
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def load_data():
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# Loading the dataset
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dataset = int(input("Choose the dataset:\n [1] web-Stanford (use this one for now)\n [2] web-BerkStan: \nEnter an option: "))
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if dataset == 1:
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if exists('../data/web-Stanford.txt'):
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dataset = '../data/web-Stanford.txt'
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else:
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print("\nThe file doesn't exist, download it from https://snap.stanford.edu/data/web-Stanford.html")
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# if there is no folder data, create it
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if not exists('../data'):
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os.makedirs('../data')
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# Downloading the dataset
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url = 'https://snap.stanford.edu/data/web-Stanford.txt.gz'
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wget.download(url, '../data/web-Stanford.txt.gz')
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# Unzipping the dataset
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with gzip.open('../data/web-Stanford.txt.gz', 'rb') as f_in:
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with open('../data/web-Stanford.txt', 'wb') as f_out:
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f_out.write(f_in.read())
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# delete the zipped file
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os.remove('../data/web-Stanford.txt.gz')
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dataset = '../data/web-Stanford.txt'
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print("\nDataset downloaded\n")
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elif dataset == 2:
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if exists('../data/web-BerkStan.txt'):
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dataset = '../data/web-BerkStan.txt'
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else:
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print("\nThe file doesn't exist, download it from https://snap.stanford.edu/data/web-BerkStan.html")
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# if there is no folder data, create it
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if not exists('../data'):
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os.makedirs('../data')
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# Downloading the dataset
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url = 'https://snap.stanford.edu/data/web-BerkStan.txt.gz'
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wget.download(url, '../data/web-BerkStan.txt.gz')
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# Unzipping the dataset
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with gzip.open('../data/web-BerkStan.txt.gz', 'rb') as f_in:
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with open('../data/web-BerkStan.txt', 'wb') as f_out:
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f_out.write(f_in.read())
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# delete the zipped file
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os.remove('../data/web-BerkStan.txt.gz')
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dataset = '../data/web-BerkStan.txt'
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print("\nDataset downloaded\n")
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return dataset
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# Creating the graph from the dataset
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def create_graph(dataset):
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print("\nCreating the graph...")
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G = nx.read_edgelist(dataset, create_using=nx.DiGraph(), nodetype=int)
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n = G.number_of_nodes()
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print("Graph created based on the dataset\n")
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return G, n
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# The matrix is filled with zeros and the (i,j) element is x if the node i is connected to the node j. Where x is 1/(number of nodes connected to i).
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def create_matrix(G):
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print("Creating the transition probability matrix...")
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P = sp.sparse.lil_matrix((n,n))
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for i in G.nodes():
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for j in G[i]: #G[i] is the list of nodes connected to i, it's neighbors
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P[i-1,j-1] = 1/len(G[i])
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print("Transition probability matrix created\n")
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return P
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# The vector is filled with d(i) = 1 if the i row of the matrix P is filled with zeros, other wise is 0
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def dangling_nodes(P,n):
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print("Creating the list of dangling nodes...")
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d = sp.sparse.lil_matrix((n,1))
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for i in range(n):
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if P[i].sum() == 0:
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d[i] = 1
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print("List of dangling nodes created\n")
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return d
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# For now it is set to equally distribute the probability to all the nodes
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def probability_vector(n):
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print("Creating the probability vector...")
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v = sp.sparse.lil_matrix((n,1))
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for i in range(n):
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v[i] = 1/n
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print("Probability vector created\n")
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return v
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def transition_matrix(P, v, d):
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print("Creating the transition matrix...")
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Pt = P + v @ (d.T)
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print("Transition matrix created\n")
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return Pt
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# it can vary from 0 to 1, the higher the value the more the probability to jump to a random page
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def alpha():
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a = []
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for i in range(85,100):
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a.append(i/100)
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return a
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# Class for plotting the results obtained. For now it can only the first algorithm. To be updated once all the algorithms are implemented and the test cases are well defined
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class Plotting:
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def tau_over_iterations(df):
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x = df['tau'][::-1].tolist()
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y = df['products m-v'].tolist()
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fig = go.Figure(data=go.Scatter(x=x, y=y, mode='lines+markers'),
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layout=go.Layout(title='products needed for the convergence', xaxis_title='tau', yaxis_title='products matrix vector'))
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# save the figure as a html file
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fig.write_html("../data/results/algo1/taus_over_prods.html")
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print("The plot has been saved in the folder data/results/algo1")
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def tau_over_time(df):
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x1 = df['tau'][::-1].tolist()
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y1 = df['time'].tolist()
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fig = go.Figure(data=go.Scatter(x=x1, y=y1, mode='lines+markers'),
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layout=go.Layout(title='Time needed for the convergence', xaxis_title='tau', yaxis_title='time (seconds)'))
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# save the plot in a html file
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fig.write_html("../data/results/algo1/taus_over_time.html")
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print("The plot has been saved in the folder data/results/algo1")
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class Algorithms:
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# Power method adapted to the PageRank problem with different damping factors. Referred as Algorithm 1 in the paper
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def algo1(Pt, v, tau, max_mv, a: list):
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start_time = time.time()
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print("STARTING ALGORITHM 1...")
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u = Pt @ v - v
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mv = 1 # number of matrix-vector multiplications
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r = sp.sparse.lil_matrix((n,1))
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Res = sp.sparse.lil_matrix((len(a),1))
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x = sp.sparse.lil_matrix((n,1))
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for i in range(len(a)):
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r = a[i]*(u)
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normed_r = norm(r)
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Res[i] = normed_r
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if Res[i] > tau:
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x = r + v
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while max(Res) > tau and mv < max_mv:
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u = Pt @ u
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mv += 1
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for i in range(len(a)):
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if Res[i] >= tau:
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r = (a[i]**(mv+1))*(u)
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Res[i] = norm(r)
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if Res[i] > tau:
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x = r + x
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if mv == max_mv:
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print("The algorithm didn't converge in ", max_mv, " iterations")
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else:
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print("The algorithm converged with ", mv, " matrix-vector multiplications executed")
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total_time = time.time() - start_time
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total_time = round(total_time, 2)
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print("The algorithm took ", total_time, " seconds to run\n")
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return mv, x, r, total_time
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# Refers to Algorithm 2 in the paper
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def Arnoldi(A,v0,m):
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v = v0
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beta = norm(v)
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v = v/beta
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H = sp.sparse.lil_matrix((m+1,m))
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V = sp.sparse.lil_matrix((A.shape[0],m+1))
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V[:,0] = v # each column of V is a vector v
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for j in range(m):
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# print("j = ", j)
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w = A @ v
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for i in range(j):
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tmp = v.T @ w # tmp is a 1x1 matrix, so it's O(1) in memory
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H[i,j] = tmp[0,0]
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w = w - H[i,j]*v
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H[j+1,j] = norm(w)
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if H[j+1,j] == 0:
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print("Arnoldi breakdown")
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m = j
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v = 0
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break
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else:
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if j < m-1:
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v = w/H[j+1,j]
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V[:,j+1] = v
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print(j, " iterations completed")
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print("V = ", V.shape)
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print("H = ", H.shape)
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print("v = ", v.shape)
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print("beta = ", beta)
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return V, H, v, beta, j
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def algo4():
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# TO DO
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pass
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class runners:
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def ShiftedPowerMethod(tau):
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dataset = Utilities.load_data()
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max_mv = 100
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G, n = Utilities.create_graph(dataset)
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P = Utilities.create_matrix(G)
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d = Utilities.dangling_nodes(P,n)
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v = Utilities.probability_vector(n)
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Pt = Utilities.transition_matrix(P, v, d)
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a = Utilities.alpha()
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mv, x, r, total_time = Algorithms.algo1(Pt, v, tau, max_mv, a)
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print("total time = ", total_time)
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# pandas dataframe to store the results
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df = pd.DataFrame(columns=['alpha', 'products m-v', 'tau', 'time'])
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# Main
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if __name__ == "__main__":
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dataset = Utilities.load_data()
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# maximum number of iterations, asked to the user
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max_mv = int(input("\nInsert the maximum number of matrix-vector operations: "))
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G, n = Utilities.create_graph(dataset)
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P = Utilities.create_matrix(G)
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d = Utilities.dangling_nodes(P,n)
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v = Utilities.probability_vector(n)
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Pt = Utilities.transition_matrix(P, v, d)
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a = Utilities.alpha()
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# run the algorithm for different values of tau from 10^-5 to 10^-9 with step 10^-1
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for i in range(5,10):
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tau = 10**(-i)
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print("\ntau = ", tau)
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mv, x, r, total_time = Algorithms.algo1(Pt, v, tau, max_mv, a)
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# store the results in the dataframe
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df = df.append({'alpha': a, 'products m-v': mv, 'tau': tau, 'time': total_time}, ignore_index=True)
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# save the results in a csv file
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df.to_csv('../data/results/algo1/different_tau.csv', index=False)
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# plot the results
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Plotting.tau_over_iterations(df)
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Plotting.tau_over_time(df)
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# print in the terminal the columns of the dataframe iterations, tau and time
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print("Computations done. Here are the results:")
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print("\n", df[['products m-v', 'tau', 'time']])
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