Improve BERT tokenization for accented characters and non-latin scripts

llama.cpp

@@ -8897,37 +8897,46 @@ struct llm_tokenizer_wpm {
     }
 
     std::vector<std::string> preprocess(const std::string & text) {
-        std::string ori_str = normalize(text);
-        uint64_t ori_size = ori_str.size();
+        // normalalization form D
+        std::vector<uint32_t> codepoints = codepoints_from_utf8(text);
+        std::vector<uint32_t> nfd_codepoints;
+        for (uint32_t code : codepoints) {
+            auto it = nfd_map.find(code);
+            if (it != nfd_map.end()) {
+                for (uint32_t c : it->second) {
+                    nfd_codepoints.push_back(c);
+                }
+            } else {
+                nfd_codepoints.push_back(code);
+            }
+        }
 
-        // single punct / single symbol / single digit
-        // baseline: add whitespace on the left and right of punct and chinese characters
-        std::vector<std::string> words;
+        // strip accents, strip control, uniformize whitespace,
+        // to lowercase, pad chinese characters, pad punctuation
         std::string new_str = "";
-        uint64_t i = 0;
-        while (i < ori_size) {
-            int utf_char_len = utf8_len(ori_str[i]);
-            if ((utf_char_len == 1) && ispunct(ori_str[i])) {
-                new_str += " ";
-                new_str += ori_str[i];
-                new_str += " ";
-                i += 1;
+        for (uint32_t code : nfd_codepoints) {
+            int type = codepoint_type(code);
+            if (type == CODEPOINT_TYPE_ACCENT_MARK || type == CODEPOINT_TYPE_CONTROL) {
+                continue;
             }
-            else if ((utf_char_len == 3) && is_chinese_char(ori_str.substr(i, 3))) {
+            code = to_lower(code);
+            if (type == CODEPOINT_TYPE_WHITESPACE) {
+                code = ' ';
+            }
+            std::string s = codepoint_to_utf8(code);
+            if (type == CODEPOINT_TYPE_PUNCTUATION || is_ascii_punct(code) || is_chinese_char(code)) {
                 new_str += " ";
-                new_str += ori_str.substr(i, 3);
+                new_str += s;
                 new_str += " ";
-                i += 3;
-            }
-            else {
-                new_str += ori_str[i];
-                i += 1;
+            } else {
+                new_str += s;
             }
         }
 
         // split by whitespace
         uint64_t l = 0;
         uint64_t r = 0;
+        std::vector<std::string> words;
         while (r < new_str.size()) {
             // if is whitespace
             if (isspace(new_str[r])) {
@@ -8945,47 +8954,22 @@ struct llm_tokenizer_wpm {
         return words;
     }
 
-    std::string normalize(const std::string & text) {
-        // TODO: handle chinese characters? https://github.com/huggingface/tokenizers/blob/ef5f50605ddf9f8caef1598c0e4853862b9707a7/tokenizers/src/normalizers/bert.rs#L98
-        std::string text2 = strip_accents(text);
-        for (size_t i = 0; i < text2.size(); i += utf8_len(text2[i])) {
-            char c = text2[i];
-            if (c >= 'A' && c <= 'Z') {
-                text2[i] = c - 'A' + 'a';
-            }
+    uint32_t to_lower(uint32_t code) {
+        if (
+            (code >= 0x041 && code <= 0x05A) || // latin
+            (code >= 0x391 && code <= 0x3A9) || // greek
+            (code >= 0x410 && code <= 0x42F)    // cyrillic
+        ) {
+            return code + 32;
         }
-        return text2;
+        return code;
     }
 
-    bool is_chinese_char(const std::string & str) {
-        int len = str.length();
-        unsigned int codepoint = 0;
-        int num_bytes = 0;
-        int i = 0;
-        unsigned char ch = static_cast<unsigned char>(str[i]);
-        if (ch <= 0x7f) {
-            codepoint = ch;
-            num_bytes = 1;
-        } else if ((ch >> 5) == 0x06) {
-            codepoint = ch & 0x1f;
-            num_bytes = 2;
-        } else if ((ch >> 4) == 0x0e) {
-            codepoint = ch & 0x0f;
-            num_bytes = 3;
-        } else if ((ch >> 3) == 0x1e) {
-            codepoint = ch & 0x07;
-            num_bytes = 4;
-        }
-        for (int j = 1; j < num_bytes; ++j) {
-            if (i + j >= len) {
-                return false; // incomplete UTF-8 character
-            }
-            unsigned char next_ch = static_cast<unsigned char>(str[i + j]);
-            if ((next_ch >> 6) != 0x02) {
-                return false; // invalid trailing byte
-            }
-            codepoint = (codepoint << 6) | (next_ch & 0x3f);
-        }
+    bool is_ascii_punct(uint32_t code) {
+        return code < 256 && ispunct(code);
+    }
+
+    bool is_chinese_char(uint32_t codepoint) {
         if ((codepoint >= 0x4E00  && codepoint <= 0x9FFF)  ||
             (codepoint >= 0x3400  && codepoint <= 0x4DBF)  ||
             (codepoint >= 0x20000 && codepoint <= 0x2A6DF) ||
@@ -9001,41 +8985,6 @@ struct llm_tokenizer_wpm {
         return false;
     }
 
-    std::string strip_accents(const std::string & input_string) {
-        std::string resultString;
-        std::map<std::string, char> accent_map = {
-            {"À", 'A'}, {"Á", 'A'}, {"Â", 'A'}, {"Ã", 'A'}, {"Ä", 'A'}, {"Å", 'A'},
-            {"à", 'a'}, {"á", 'a'}, {"â", 'a'}, {"ã", 'a'}, {"ä", 'a'}, {"å", 'a'},
-            {"È", 'E'}, {"É", 'E'}, {"Ê", 'E'}, {"Ë", 'E'}, {"è", 'e'}, {"é", 'e'},
-            {"ê", 'e'}, {"ë", 'e'}, {"Ì", 'I'}, {"Í", 'I'}, {"Î", 'I'}, {"Ï", 'I'},
-            {"ì", 'i'}, {"í", 'i'}, {"î", 'i'}, {"ï", 'i'}, {"Ò", 'O'}, {"Ó", 'O'},
-            {"Ô", 'O'}, {"Õ", 'O'}, {"Ö", 'O'}, {"ò", 'o'}, {"ó", 'o'}, {"ô", 'o'},
-            {"õ", 'o'}, {"ö", 'o'}, {"Ù", 'U'}, {"Ú", 'U'}, {"Û", 'U'}, {"Ü", 'U'},
-            {"ù", 'u'}, {"ú", 'u'}, {"û", 'u'}, {"ü", 'u'}, {"Ý", 'Y'}, {"ý", 'y'},
-            {"Ç", 'C'}, {"ç", 'c'}, {"Ñ", 'N'}, {"ñ", 'n'},
-        };
-
-        for (size_t i = 0; i <  input_string.length();) {
-            int len = utf8_len(input_string[i]);
-            std::string curChar = input_string.substr(i, len);
-            auto iter = accent_map.find(curChar);
-            if (iter != accent_map.end()) {
-                resultString += iter->second;
-            } else {
-                resultString += curChar;
-            }
-            i += len;
-        }
-
-        return resultString;
-    }
-
-    static size_t utf8_len(char src) {
-        const size_t lookup[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4};
-        uint8_t highbits = static_cast<uint8_t>(src) >> 4;
-        return lookup[highbits];
-    }
-
     const llama_vocab & vocab;
 };