mac下安装tensorflow及入门例子

https://www.tensorflow.org/install/install_mac

使用virtualenv安装，virtualenv相当于使tensorflow运行在虚拟机环境下。

需要使用source ~/tensorflow/bin/activate 命令，(我安装在了

source /Users/work/builded/tensorflow/bin/activate，bash下/是硬盘根目录，~/是用户根目录）

命令行变成 (tensorflow)$ 这样，才可以使用 import tensorflow as tf这些

使用ptython运行一个简单的y = -x +1训练模型：

(tensorflow) $ python tftrain.py

import numpy as np
import tensorflow as tf

# Model parameters
W = tf.Variable([.3], tf.float32)
b = tf.Variable([-.3], tf.float32)
# Model input and output
x = tf.placeholder(tf.float32)
linear_model = W * x + b
y = tf.placeholder(tf.float32)
# loss
loss = tf.reduce_sum(tf.square(linear_model - y)) # sum of the squares
# optimizer
optimizer = tf.train.GradientDescentOptimizer(0.01)
train = optimizer.minimize(loss)
# training data
x_train = [1,2,3,4]
y_train = [0,-1,-2,-3]
# training loop
init = tf.global_variables_initializer()
sess = tf.Session()
sess.run(init) # reset values to wrong
for i in range(1000):
  sess.run(train, {x:x_train, y:y_train})

# evaluate training accuracy
curr_W, curr_b, curr_loss  = sess.run([W, b, loss], {x:x_train, y:y_train})
print("W: %s b: %s loss: %s"%(curr_W, curr_b, curr_loss))