opt4_8_backward.py

#coding:utf-8
#0导入模块 ，生成模拟数据集
import tensorflow as tf
import numpy as np
import matplotlib.pyplot as plt
import opt4_8_generateds
import opt4_8_forward

STEPS = 40000
BATCH_SIZE = 30 
LEARNING_RATE_BASE = 0.001
LEARNING_RATE_DECAY = 0.999
REGULARIZER = 0.01

def backward():
	x = tf.placeholder(tf.float32, shape=(None, 2))
	y_ = tf.placeholder(tf.float32, shape=(None, 1))

	X, Y_, Y_c = opt4_8_generateds.generateds()

	y = opt4_8_forward.forward(x, REGULARIZER)
	
	global_step = tf.Variable(0,trainable=False)	

	learning_rate = tf.train.exponential_decay(
		LEARNING_RATE_BASE,
		global_step,
		300/BATCH_SIZE,
		LEARNING_RATE_DECAY,
		staircase=True)


	#定义损失函数
	loss_mse = tf.reduce_mean(tf.square(y-y_))
	loss_total = loss_mse + tf.add_n(tf.get_collection('losses'))
	
	#定义反向传播方法：包含正则化
	train_step = tf.train.AdamOptimizer(learning_rate).minimize(loss_total)

	with tf.Session() as sess:
		init_op = tf.global_variables_initializer()
		sess.run(init_op)
		for i in range(STEPS):
			start = (i*BATCH_SIZE) % 300
			end = start + BATCH_SIZE
			sess.run(train_step, feed_dict={x: X[start:end], y_:Y_[start:end]})
			if i % 2000 == 0:
				loss_v = sess.run(loss_total, feed_dict={x:X,y_:Y_})
				print("After %d steps, loss is: %f" %(i, loss_v))

		xx, yy = np.mgrid[-3:3:.01, -3:3:.01]
		grid = np.c_[xx.ravel(), yy.ravel()]
		probs = sess.run(y, feed_dict={x:grid})
		probs = probs.reshape(xx.shape)
	
	plt.scatter(X[:,0], X[:,1], c=np.squeeze(Y_c)) 
	plt.contour(xx, yy, probs, levels=[.5])
	plt.show()
	
if __name__=='__main__':
	backward()