# 25428.0 25891.5 26446.5
# [1002.1399999999994, 223.21665372403237, -1291.848080071952, 1515.5600276924624, -1404.8070879687737, -887.5562485642265, -2129.790874533273, 1268.8912058979067, -893.1255882425288, -358.771941045434, 1161.2662431910446, -499.8519798398823, -806.2229919825804]

import random
from datetime import datetime
import matplotlib.pyplot as plt

class PLA():
	def __init__(self, data):
		self.data = data
		self.dim = len(self.data[0]['x'])
		self.w = [0] * self.dim

	def iterate(self):
		'''
			randomly picks an example (x_n, y_n) in every iteration.
			updates wt if and only if w_t is incorrect on the example.

			Inputs:
				None
			Outputs:
				mistake: bool.
		'''
		index = random.randint(0, len(data)-1)
		mistake = 1 if sign(dot(self.w, self.data[index]['x'])) != self.data[index]['y'] else 0
		if mistake:
			self.update(index)
		return mistake

	def update(self, index):
		'''
			w_(t+1) = w_t + y_t*x_t

			Inputs:
				index: which row need to use for updating weight
			Outputs:
				None
		'''
		for i in range(self.dim):
			self.w[i] = self.w[i] + self.data[index]['y'] * self.data[index]['x'][i]

def read_file():
	'''
		read numbers from 'hw1_train.dat'

		Inputs:
			None
		Outputs:
			data: dict list. each dict has ('x', 'y') pair
				x is a list contains 12 numbers.
				y is either 1 or -1.
	'''
	with open('hw1_train.dat') as fp:
		data = []
		lines = fp.readlines()[:-1]
		for line in lines:
			numbers = line.split()
			x = [ float(i) for i in numbers[:-1] ]
			x.insert(0,11.26)
			y = int(numbers[-1])

			data.append({
				'x': x,
				'y': y,
			})
	return data

def dot(a, b):
	'''
		dot product

		Inputs:
			a: a list
			b: a list. its length must be equal to len(a)
		Outputs:
			ans: a number
	'''
	ans = 0
	assert len(a)==len(b)
	for i in range(len(a)):
		ans += a[i] * b[i]
	return ans

def sign(a):
	'''
		positive || negative

		Inputs:
			a: a number
		Outputs:
			ans: 1 or -1, means this is positive or negative
	'''
	return 1 if a>0 else -1

if __name__ == '__main__':
	data = read_file()
	log = []
	for i in range(1000):
		random.seed(datetime.now().timestamp())
		pla = PLA(data)

		counter = 0
		stopping_counter = 0
		while 1:
			mistake = pla.iterate()
			counter += 1
			if mistake:
				stopping_counter = 0
			else:
				stopping_counter += 1
			if stopping_counter == (5*len(data)):
				break
		log.append(counter)

	sorted_log = sorted(log)
	print("medium: {}".format((sorted_log[499]+sorted_log[500])/2))
	plt.hist(log, bins=100)
	plt.savefig('./hw1_11.png')
	plt.show()
	print(pla.w)