import tensorflow as tf
print(tf.__version__)	# 1.9.0

x = tf.Variable(0.)
y = tf.Variable(1.)
print(x)
print(y)
# 构建计算图
# x = x + y
add_op = x.assign(x +y)
# y = y / 2
div_op = y.assign(y / 2)

with tf.Session() as sess:
    sess.run(tf.global_variables_initializer())
    for i in range(50):
        sess.run(add_op)
        sess.run(div_op)
    print(x.eval())

import tensorflow as tf
print(tf.__version__)   # 2.0.0

x = tf.constant(0.)
y = tf.constant(1.)

for i in range(50):
    x = x + y
    y = y / 2
print(x.numpy())

import torch
print(torch.__version__)    # 1.4.0

x = torch.Tensor([0.])
y = torch.Tensor([1.])
for i in range(50):
    x = x + y
    y = y / 2
print(x)