python之tensorflow 张量板错误 : you must feed a value for placeholder tensor

初学者并尝试在我的 tensorflow prgm 中使用 tensorboard。我按照在教程中看到的那样添加了 tensorboard refs，但我收到以下错误消息:

InvalidArgumentError (see above for traceback): You must feed a value for placeholder tensor 'x' with dtype float [[Node: x = Placeholderdtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]]

错误似乎与我在训练循环中添加的这一行有关。没有这一行，程序不会抛出任何错误:

summary = sess.run(merged_summary_op, {x: x_train, y_prim: y_train}) 

谢谢，如果有人可以检查我下面的代码并提供帮助:

# -*- coding: utf-8 -*- 
 
import tensorflow as tf 
sess = tf.Session() 
 
# parms 
a = tf.Variable([2.0], dtype=tf.float32, name="a") 
x = tf.placeholder(tf.float32, name="x") 
b = tf.Variable([1.0], dtype=tf.float32, name="b") 
 
# model : y=ax+b 
with tf.name_scope('Model'): 
    y = tf.add ((tf.multiply(a, x)), b) 
 
# info for TensorBoard  
writer = tf.summary.FileWriter("D:\\tmp\\tensorflow\\logs", sess.graph) 
 
# loss fct - mean square error 
with tf.name_scope('cost'): 
    y_prim = tf.placeholder(tf.float32) 
    cost = tf.reduce_sum(tf.square(y - y_prim)) 
 
# optimizer = gradientdescent 
with tf.name_scope('GradDes'): 
    optimizer = tf.train.GradientDescentOptimizer(0.01) 
    train = optimizer.minimize(cost) 
 
# train datas  
x_train = [1, 2, 3, 4] 
y_train = [5.2, 8.4, 11.1, 14.7] 
 
# summary for Tensorboard 
tf.summary.scalar("cost", cost) 
merged_summary_op = tf.summary.merge_all() 
 
# init vars 
init = tf.global_variables_initializer() 
 
# train loop 
sess.run(init)   
for i in range (500): 
    sess.run([train, cost], feed_dict={x: x_train, y_prim: y_train}) 
    summary = sess.run(merged_summary_op, {x: x_train, y_prim: y_train}) 
    a_found, b_found, curr_cost = sess.run([a, b, cost], feed_dict={x:x_train, y_prim: y_train})  
    print("iteration :", i, "a: ", a_found, "b: ", b_found, "cost: ",curr_cost) 

请您参考如下方法:

不要在单独的 sess.run 中执行合并的汇总操作。试试这个:

a_found, b_found, curr_cost, summary = sess.run([a, b, cost, merged_summary_op], feed_dict={x:x_train, y_prim: y_train})  

session 运行后，您需要调用 FileWriter 的 add_summary 方法:

writer.add_summary(summary) 
writer.flush()