WikiText数据集_自然语言处理

WikiText数据集来自维基百科(Wiki)的词条，经过验证的优质文章内容被收录，总数超过1亿个单词(原词叫token，令牌，就是句子拆分为单词的数量)。

与Penn Treebank（PTB）的预处理版本相比，WikiText-2要大2倍多，WikiText-103要大110倍多。WikiText数据集还具有更大的词汇表，并保留了原始大小写、标点符号和数字，所有这些都在PTB中删除。由于数据集由完整的文章组成，因此它非常适合可以利用长期依赖关系的模型。

WikiText-2 约 4.3 MB，WikiText-103 约 181 MB。

示例

数据集保存在txt中，大概的格式如下：

= Homarus gammarus = Homarus gammarus , known as the European lobster or common lobster , is a species of <unk> lobster from the eastern Atlantic Ocean , Mediterranean Sea and parts of the Black Sea . It is closely related to the American lobster , H. americanus . It may grow to a length of 60 cm ( 24 in ) and a mass of 6 kilograms ( 13 lb ) , and bears a conspicuous pair of claws . In life , the lobsters are blue , only becoming " lobster red " on cooking . Mating occurs in the summer , producing eggs which are carried by the females for up to a year before hatching into <unk> larvae . Homarus gammarus is a highly esteemed food , and is widely caught using lobster pots , mostly around the British Isles . = = Description = = Homarus gammarus is a large <unk> , with a body length up to 60 centimetres ( 24 in ) and weighing up to 5 – 6 kilograms ( 11 – 13 lb ) , although the lobsters caught in lobster pots are usually 23 – 38 cm ( 9 – 15 in ) long and weigh 0 @.@ 7 – 2 @.@ 2 kg ( 1 @.@ 5 – 4 @.@ 9 lb ) . Like other crustaceans , lobsters have a hard <unk> which they must shed in order to grow , in a process called <unk> ( <unk> ) . This may occur several times a year for young lobsters , but decreases to once every 1 – 2 years for larger animals . The first pair of <unk> is armed with a large , asymmetrical pair of claws . The larger one is the " <unk> " , and has rounded <unk> used for crushing prey ; the other is the " cutter " , which has sharp inner edges , and is used for holding or tearing the prey . Usually , the left claw is the <unk> , and the right is the cutter . The <unk> is generally blue above , with spots that <unk> , and yellow below . The red colour associated with lobsters only appears after cooking . This occurs because , in life , the red pigment <unk> is bound to a protein complex , but the complex is broken up by the heat of cooking , releasing the red pigment . The closest relative of H. gammarus is the American lobster , Homarus americanus . The two species are very similar , and can be crossed artificially , although hybrids are unlikely to occur in the wild since their ranges do not overlap . The two species can be distinguished by a number of characteristics : The <unk> of H. americanus bears one or more spines on the underside , which are lacking in H. gammarus . The spines on the claws of H. americanus are red or red @-@ tipped , while those of H. gammarus are white or white @-@ tipped . The underside of the claw of H. americanus is orange or red , while that of H. gammarus is creamy white or very pale red . = = Life cycle = = Female H. gammarus reach sexual maturity when they have grown to a carapace length of 80 – 85 millimetres ( 3 @.@ 1 – 3 @.@ 3 in ) , whereas males mature at a slightly smaller size . Mating typically occurs in summer between a recently <unk> female , whose shell is therefore soft , and a hard @-@ shelled male . The female carries the eggs for up to 12 months , depending on the temperature , attached to her <unk> . Females carrying eggs are said to be " <unk> " and can be found throughout the year . The eggs hatch at night , and the larvae swim to the water surface where they drift with the ocean currents , preying on <unk> . This stage involves three <unk> and lasts for 15 – 35 days . After the third moult , the juvenile takes on a form closer to the adult , and adopts a <unk> lifestyle . The juveniles are rarely seen in the wild , and are poorly known , although they are known to be capable of digging extensive burrows . It is estimated that only 1 larva in every 20 @,@ 000 survives to the <unk> phase . When they reach a carapace length of 15 mm ( 0 @.@ 59 in ) , the juveniles leave their burrows and start their adult lives . .....

以上例子是词条 = Homarus gammarus =的介绍（一种龙虾品种）。其也是wiki词条下的一级标题，后面的 = = Description = = 和 = = Life cycle = = 是二级标题，大意为“简述”和“生命周期“。
同理，=== xxx === 这样的格式就是该词条下的三级标题。

这里需要注意，一个一级标题下的内容称为一篇文章(Article)，下面可以有几个二级标题和三级标题，以及对应的内容。

标识符

这里需要注意NLP里面常用的标识符经常出现

<unk>

意思是这个单词是低频词，不在统计词频范围内

这个是连接符，比如词条中有one-apple,那么数据库文本中是这样记录 one @-@ apple

<eos>

一段话结尾所添加的标识符，一般是一段话存在一个string中，之后split成为一个列表，列表最后一个元素是<eos>

处理方式

处理需要建立一个语料库(Corpus)，一般构造一个字典(Dictionary)来索引(index)全部单词(vocab/words)。
wikitext-2 的Corpus共 33,278个不同的单词。 wikitext-101的Corpus共267,735个不同的单词。文本由这些词组成，字典格式如下

{ 单词A：0 ； 单词B：1 ；... ；单词X：N}

官方给出的数据统计：

这里需要注意Tokens, 它是整个数据库文本拆分为单词后，单词的统计总量，是有顺序的。

另外如果按行统计的话(就是<eos>隔断)， Train, Valid, Test三者的量为36718, 3760, 4358

下载和参考文献

https://blog.salesforceairesearch.com/the-wikitext-long-term-dependency-language-modeling-dataset/
https://paperswithcode.com/dataset/wikitext-2