一袋文字模型：2個PHP函數，結果相同：爲什麼？

Question

我有兩個PHP函數來計算兩個文本之間的關係。他們都使用文字模型包，但check2（）更快。無論如何，這兩個函數都有相同的結果。爲什麼？ check1（）使用一個包含所有單詞的大型字典數組 - 如單詞模型包中所述。 check2（）不使用一個大數組，而是隻包含一個文本單詞的數組。所以check2（）不應該工作，但它沒有。爲什麼這兩個函數都有相同的結果？

function check1($terms_in_article1, $terms_in_article2) { 
    global $zeit_check1; 
    $zeit_s = microtime(TRUE); 
    $length1 = count($terms_in_article1); // number of words 
    $length2 = count($terms_in_article2); // number of words 
    $all_terms = array_merge($terms_in_article1, $terms_in_article2); 
    $all_terms = array_unique($all_terms); 
    foreach ($all_terms as $all_termsa) { 
     $term_vector1[$all_termsa] = 0; 
     $term_vector2[$all_termsa] = 0; 
    } 
    foreach ($terms_in_article1 as $terms_in_article1a) { 
     $term_vector1[$terms_in_article1a]++; 
    } 
    foreach ($terms_in_article2 as $terms_in_article2a) { 
     $term_vector2[$terms_in_article2a]++; 
    } 
    $score = 0; 
    foreach ($all_terms as $all_termsa) { 
     $score += $term_vector1[$all_termsa]*$term_vector2[$all_termsa]; 
    } 
    $score = $score/($length1*$length2); 
    $score *= 500; // for better readability 
    $zeit_e = microtime(TRUE); 
    $zeit_check1 += ($zeit_e-$zeit_s); 
    return $score; 
} 
function check2($terms_in_article1, $terms_in_article2) { 
    global $zeit_check2; 
    $zeit_s = microtime(TRUE); 
    $length1 = count($terms_in_article1); // number of words 
    $length2 = count($terms_in_article2); // number of words 
    $score_table = array(); 
    foreach($terms_in_article1 as $term){ 
     if(!isset($score_table[$term])) $score_table[$term] = 0; 
     $score_table[$term] += 1; 
    } 
    $score_table2 = array(); 
    foreach($terms_in_article2 as $term){ 
     if(isset($score_table[$term])){ 
      if(!isset($score_table2[$term])) $score_table2[$term] = 0; 
      $score_table2[$term] += 1; 
     } 
    } 
    $score = 0; 
    foreach($score_table2 as $key => $entry){ 
     $score += $score_table[$key] * $entry; 
    } 
    $score = $score/($length1*$length2); 
    $score *= 500; 
    $zeit_e = microtime(TRUE); 
    $zeit_check2 += ($zeit_e-$zeit_s); 
    return $score; 
} 

我希望你能幫助我。提前致謝！

Answer 1

這兩個函數都實現了幾乎相同的算法，但第一個函數以直接的方式執行，第二個函數更聰明一點，並跳過一部分不必要的工作。

CHECK1是這樣的：

// loop length(words1) times 
for each word in words1: 
    freq1[word]++ 

// loop length(words2) times 
for each word in words2: 
    freq2[word]++ 

// loop length(union(words1, words2)) times 
for each word in union(words1, words2): 
    score += freq1[word] * freq2[word] 

但要記住：當你的東西乘以零，你會得到零。

這意味着，計算不在兩組中的單詞的頻率是浪費時間 - 我們將頻率乘以零，這將不增加分數。

CHECK2考慮到了這：

// loop length(words1) times 
for each word in words1: 
    freq1[word]++ 

// loop length(words2) times 
for each word in words2: 
    if freq1[word] > 0: 
     freq2[word]++ 

// loop length(intersection(words1, words2)) times 
for each word in freq2: 
    score += freq1[word] * freq2[word] 

Answer 2

因爲你似乎關心性能，這裏的算法在你的CHECK2功能的優化版，使用了一些更多的內置功能，以提高速度。

function check ($terms1, $terms2) 
{ 
    $counts1 = array_count_values($terms1); 
    $totalScore = 0; 
    foreach ($terms2 as $term) { 
     if (isset($counts1[$term])) $totalScore += $counts1[$term]; 
    } 
    return $totalScore * 500/(count($terms1) * count($terms2)); 
}