MNIST機器學習入門

2021-08-19 16:07:57 字數 1710 閱讀 8822

路漫漫其修遠兮

環境：python + tensorflow

from __future__ import absolute_import


from __future__ import division


from __future__ import print_function


# pylint: disable=unused-import


import gzip


import os


import tempfile


import numpy


from six.moves import urllib


from six.moves import xrange # pylint: disable=redefined-builtin


import tensorflow as tf


from tensorflow.contrib.learn.python.learn.datasets.mnist import read_data_sets


# pylint: enable=unused-import
2. softmax模型訓練

import input_data


import tensorflow as tf


#建立互動會話類


sess = tf.interactivesession()


x = tf.placeholder("float", shape = [none, 784]) #輸入資料，28*28 = 784


y_ = tf.placeholder("float", shape = [none, 10]) #標籤資料，表示類別 0~9


w = tf.variable(tf.zeros([784,10])) #weight


b = tf.variable(tf.zeros([10])) #bias


sess.run(tf.global_variables_initializer()) #初始化變數


#**模型 softmax


y = tf.nn.softmax(tf.matmul(x,w) + b)


#損失函式 交叉熵


cross_entropy = -tf.reduce_sum(y_*tf.log(y))


#梯度下降


train_step = tf.train.gradientdescentoptimizer(0.01).minimize(cross_entropy)


#訓練1000次


for _ in range(1000):


batch = mnist_data.train.next_batch(50)


train_step.run(feed_dict = )


#評估模型


correct_prediction = tf.equal(tf.arg_max(y,1), tf.arg_max(y_,1))


accuracy = tf.reduce_mean(tf.cast(correct_prediction, "float"))


print(accuracy.eval(feed_dict = ))


sess.close()
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