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ipd_exact.py
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ipd_exact.py
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# coding: utf-8
import numpy as np
import matplotlib.pyplot as plt
import torch
import torch.nn as nn
from torch.distributions import Bernoulli
from copy import deepcopy
from envs import IPD
class Hp():
def __init__(self):
self.lr_out = 0.2
self.lr_in = 0.3
self.gamma = 0.96
self.n_update = 50
self.len_rollout = 200
self.batch_size = 64
self.seed = 42
hp = Hp()
ipd = IPD(hp.len_rollout, hp.batch_size)
def phi(x1,x2):
return [x1*x2, x1*(1-x2), (1-x1)*x2,(1-x1)*(1-x2)]
def true_objective(theta1, theta2, ipd):
p1 = torch.sigmoid(theta1)
p2 = torch.sigmoid(theta2[[0,1,3,2,4]])
p0 = (p1[0], p2[0])
p = (p1[1:], p2[1:])
# create initial laws, transition matrix and rewards:
P0 = torch.stack(phi(*p0), dim=0).view(1,-1)
P = torch.stack(phi(*p), dim=1)
R = torch.from_numpy(ipd.payout_mat).view(-1,1).float()
# the true value to optimize:
objective = (P0.mm(torch.inverse(torch.eye(4) - hp.gamma*P))).mm(R)
return -objective
def act(batch_states, theta):
batch_states = torch.from_numpy(batch_states).long()
probs = torch.sigmoid(theta)[batch_states]
m = Bernoulli(1-probs)
actions = m.sample()
log_probs_actions = m.log_prob(actions)
return actions.numpy().astype(int), log_probs_actions
def get_gradient(objective, theta):
# create differentiable gradient for 2nd orders:
grad_objective = torch.autograd.grad(objective, (theta), create_graph=True)[0]
return grad_objective
def step(theta1, theta2):
# just to evaluate progress:
(s1, s2), _ = ipd.reset()
score1 = 0
score2 = 0
for t in range(hp.len_rollout):
a1, lp1 = act(s1, theta1)
a2, lp2 = act(s2, theta2)
(s1, s2), (r1, r2),_,_ = ipd.step((a1, a2))
# cumulate scores
score1 += np.mean(r1)/float(hp.len_rollout)
score2 += np.mean(r2)/float(hp.len_rollout)
return (score1, score2)
class Agent():
def __init__(self, theta=None):
# init theta and its optimizer
self.theta = nn.Parameter(torch.zeros(5, requires_grad=True))
self.theta_optimizer = torch.optim.Adam((self.theta,),lr=hp.lr_out)
def theta_update(self, objective):
self.theta_optimizer.zero_grad()
objective.backward(retain_graph=True)
self.theta_optimizer.step()
def in_lookahead(self, other_theta):
other_objective = true_objective(other_theta, self.theta, ipd)
grad = get_gradient(other_objective, other_theta)
return grad
def out_lookahead(self, other_theta):
objective = true_objective(self.theta, other_theta, ipd)
self.theta_update(objective)
def play(agent1, agent2, n_lookaheads):
print("start iterations with", n_lookaheads, "lookaheads:")
joint_scores = []
for update in range(hp.n_update):
# copy other's parameters:
theta1_ = torch.tensor(agent1.theta.detach(), requires_grad=True)
theta2_ = torch.tensor(agent2.theta.detach(), requires_grad=True)
for k in range(n_lookaheads):
# estimate other's gradients from in_lookahead:
grad2 = agent1.in_lookahead(theta2_)
grad1 = agent2.in_lookahead(theta1_)
# update other's theta
theta2_ = theta2_ - hp.lr_in * grad2
theta1_ = theta1_ - hp.lr_in * grad1
# update own parameters from out_lookahead:
agent1.out_lookahead(theta2_)
agent2.out_lookahead(theta1_)
# evaluate:
score = step(agent1.theta, agent2.theta)
joint_scores.append(0.5*(score[0] + score[1]))
# print
if update%10==0 :
p1 = [p.item() for p in torch.sigmoid(agent1.theta)]
p2 = [p.item() for p in torch.sigmoid(agent2.theta)]
print('update', update, 'score (%.3f,%.3f)' % (score[0], score[1]) , 'policy (agent1) = {%.3f, %.3f, %.3f, %.3f, %.3f}' % (p1[0], p1[1], p1[2], p1[3], p1[4]),' (agent2) = {%.3f, %.3f, %.3f, %.3f, %.3f}' % (p2[0], p2[1], p2[2], p2[3], p2[4]))
return joint_scores
# plot progress:
if __name__=="__main__":
colors = ['b','c','m','r']
for i in range(4):
torch.manual_seed(hp.seed)
scores = np.array(play(Agent(), Agent(), i))
plt.plot(scores, colors[i], label=str(i)+" lookaheads")
plt.legend()
plt.xlabel('rollouts')
plt.ylabel('joint score')
plt.show()