当我使用 TensorFlow 解码“csv”文件时，如何将“tf.map_fn”应用于 SparseTensor？

Question

当我使用以下代码时

import tensorflow as tf

# def input_pipeline(filenames, batch_size):
#     # Define a `tf.contrib.data.Dataset` for iterating over one epoch of the data.
#     dataset = (tf.contrib.data.TextLineDataset(filenames)
#                .map(lambda line: tf.decode_csv(
#                     line, record_defaults=[['1'], ['1'], ['1']], field_delim='-'))
#                .shuffle(buffer_size=10)  # Equivalent to min_after_dequeue=10.
#                .batch(batch_size))

#     # Return an *initializable* iterator over the dataset, which will allow us to
#     # re-initialize it at the beginning of each epoch.
#     return dataset.make_initializable_iterator() 

def decode_func(line):
    record_defaults = [['1'],['1'],['1']]
    line = tf.decode_csv(line, record_defaults=record_defaults, field_delim='-')
    str_to_int = lambda r: tf.string_to_number(r, tf.int32)
    query = tf.string_split(line[:1], ",").values
    title = tf.string_split(line[1:2], ",").values
    query = tf.map_fn(str_to_int, query, dtype=tf.int32)
    title = tf.map_fn(str_to_int, title, dtype=tf.int32)
    label = line[2]
    return query, title, label

def input_pipeline(filenames, batch_size):
    # Define a `tf.contrib.data.Dataset` for iterating over one epoch of the data.
    dataset = tf.contrib.data.TextLineDataset(filenames)
    dataset = dataset.map(decode_func)
    dataset = dataset.shuffle(buffer_size=10)  # Equivalent to min_after_dequeue=10.
    dataset = dataset.batch(batch_size)

    # Return an *initializable* iterator over the dataset, which will allow us to
    # re-initialize it at the beginning of each epoch.
    return dataset.make_initializable_iterator() 


filenames=['2.txt']
batch_size = 3
num_epochs = 10
iterator = input_pipeline(filenames, batch_size)

# `a1`, `a2`, and `a3` represent the next element to be retrieved from the iterator.    
a1, a2, a3 = iterator.get_next()

with tf.Session() as sess:
    for _ in range(num_epochs):
        print(_)
        # Resets the iterator at the beginning of an epoch.
        sess.run(iterator.initializer)
        try:
            while True:
                a, b, c = sess.run([a1, a2, a3])
                print(type(a[0]), b, c)
        except tf.errors.OutOfRangeError:
            print('stop')
            # This will be raised when you reach the end of an epoch (i.e. the
            # iterator has no more elements).
            pass                 

        # Perform any end-of-epoch computation here.
        print('Done training, epoch reached')

脚本崩溃没有返回任何结果，并在到达a, b, c = sess.run([a1, a2, a3])时停止，但是当我评论时

query = tf.map_fn(str_to_int, query, dtype=tf.int32)
title = tf.map_fn(str_to_int, title, dtype=tf.int32)

它工作并返回结果。

2.txt中的数据格式是这样的

1,2,3-4,5-0
1-2,3,4-1
4,5,6,7,8-9-0

另外，为什么返回结果是byte-like对象而不是str？

Answer 1

我看了看，如果你更换：

query = tf.map_fn(str_to_int, query, dtype=tf.int32)
title = tf.map_fn(str_to_int, title, dtype=tf.int32)
label = line[2]

通过

query = tf.string_to_number(query, out_type=tf.int32)
title = tf.string_to_number(title, out_type=tf.int32)
label = tf.string_to_number(line[2], out_type=tf.int32)

效果很好。

似乎有 2 个嵌套的 TensorFlow lambda 函数（tf.map_fn 和 DataSet.map）只是不起作用。幸运的是，它过于复杂了。

关于你的第二个问题，我得到了这个作为输出：

[(array([4, 5, 6, 7, 8], dtype=int32), array([9], dtype=int32), 0)]
<type 'numpy.ndarray'>