为什么这个循环运行得这么慢:C#

所以我正在做一个文本挖掘项目，目前正在尝试实现信息增益。我有一个数据，其中每行描绘一个文档。因此，换行符会拆分不同的文档。

我必须生成一个矩阵，其中列是所有文档中的所有不同单词，行是不同的文档。 此表中的每个单元格都是 1（true） 或 0（false），表示该单词是否存在于该文档中。文档987篇，总字数22860字，不同字数3680字。所以3680个单词与22860个单词进行比较。这运行缓慢，但很好。花费更多时间的循环是当我遍历单词列表的对象以生成矩阵时。见下文

注意：我已经删除了文档中的所有重复单词。

 class word_list
        {
            public string word;
            public List<bool> doc= new List<bool>();
        };//class ends
        private void button2_Click(object sender, EventArgs e)
        {
            //Convert the string into an array of words 
            string[] w1 = richTextBox1.Text.Trim().Split(''n',' ').Select(x => x.Trim().ToLower()).Distinct().ToArray(); //all distinct words
            string[] rich_doc = richTextBox1.Text.Trim().Split(''n'); //all documents array
            List<word_list> words = new List<word_list>();
            richTextBox2.Text+=("no. of distict words: " + w1.Length + ", no. of docs " + rich_doc.Length);
            for (int i = 0; i < w1.Length; i++)
            {
                word_list temp = new word_list();
                temp.word = w1[i]; //temp has the current distict word as class object
                for(int j=0;j<rich_doc.Length;j++)//traverse all doc array
                {
                    temp.doc.Add(false);
                    List<string> doc_word = Regex.Split(rich_doc[j], @"'b").Distinct(StringComparer.CurrentCultureIgnoreCase).ToList();
                    //richTextBox2.Text += ("'n no. of words in this doc: " + doc_word.Count);
                    //richTextBox2.SelectionStart = richTextBox1.Text.Length;
                    //richTextBox2.Focus();
                    int doc_count = doc_word.Count; // number of docs
                    for (int k = 0; k < doc_count; k++)//All words in a doc are compared
                    {
                        if(doc_word[k].ToLower() == w1[i].ToLower())
                        {
                            temp.doc[temp.doc.Count-1]=true;                            
                            break;
                        }
                    }                      
                }
                if ((words.Count - 1)>=0)
                    richTextBox2.Text += ("'n word(" + words.Count + "/" + w1.Length + "): " + words[words.Count - 1].word);
                richTextBox2.SelectionStart = richTextBox1.Text.Length;
                richTextBox2.Focus();
                words.Add(temp);
            }
            //generate matrix
            int t = rich_doc.Length; //no. of docs
            int word_count = words.Count;
            richTextBox1.Text = "Doc";
            foreach (word_list w in words)
            {
                richTextBox1.Text += "'t" + w.word;
            }
            richTextBox1.Text += "'n";
//This loop is slow
            for (int i = 0; i < t; i++) //traverse through number of docs
            {
                richTextBox1.Text += i + 1;
                for (int h = 0; h < word_count; h++)//traverse through each distinct word in the list
                {
                    if (words[h].doc[i])
                        richTextBox1.Text += "'t1";
                    else
                        richTextBox1.Text += "'t0";
                }
                richTextBox1.Text += "'n";
            }
        }//end of button 2

        //generate matrix
        StringBuilder sb = new StringBuilder();
        int t = rich_doc.Length; //no. of docs
        int word_count = words.Count;
        richTextBox1.Text = "Doc";
        foreach (word_list w in words)
        {
            sb.Append("'t");
            sb.Append(w.word);
        }
        sb.AppendLine();
        //This loop is not slow anymore :)
        for (int i = 0; i < t; i++) //traverse through number of docs
        {
            sb.Append(i + 1);
            for (int h = 0; h < word_count; h++)//traverse through each distinct word in the list
            {
                if (words[h].doc[i])
                    sb.Append("'t1");
                else
                    sb.Append("'t0");
            }
            sb.AppendLine();
        }
        richTextBox1.Text = sb.ToString();