Add bigram lookup implementation.
Bug: 5046459
Change-Id: Id2c7686c5da078751ed587e559417e808779aa7a
diff --git a/native/src/bigram_dictionary.cpp b/native/src/bigram_dictionary.cpp
index 6ed4d09..c340c6c 100644
--- a/native/src/bigram_dictionary.cpp
+++ b/native/src/bigram_dictionary.cpp
@@ -21,13 +21,14 @@
#include "bigram_dictionary.h"
#include "dictionary.h"
+#include "binary_format.h"
namespace latinime {
BigramDictionary::BigramDictionary(const unsigned char *dict, int maxWordLength,
int maxAlternatives, const bool isLatestDictVersion, const bool hasBigram,
Dictionary *parentDictionary)
- : DICT(dict), MAX_WORD_LENGTH(maxWordLength),
+ : DICT(dict + NEW_DICTIONARY_HEADER_SIZE), MAX_WORD_LENGTH(maxWordLength),
MAX_ALTERNATIVES(maxAlternatives), IS_LATEST_DICT_VERSION(isLatestDictVersion),
HAS_BIGRAM(hasBigram), mParentDictionary(parentDictionary) {
if (DEBUG_DICT) {
@@ -82,169 +83,64 @@
return false;
}
-int BigramDictionary::getBigramAddress(int *pos, bool advance) {
- int address = 0;
-
- address += (DICT[*pos] & 0x3F) << 16;
- address += (DICT[*pos + 1] & 0xFF) << 8;
- address += (DICT[*pos + 2] & 0xFF);
-
- if (advance) {
- *pos += 3;
- }
-
- return address;
-}
-
-int BigramDictionary::getBigramFreq(int *pos) {
- int freq = DICT[(*pos)++] & FLAG_BIGRAM_FREQ;
-
- return freq;
-}
-
-
+/* Parameters :
+ * prevWord: the word before, the one for which we need to look up bigrams.
+ * prevWordLength: its length.
+ * codes: what user typed, in the same format as for UnigramDictionary::getSuggestions.
+ * codesSize: the size of the codes array.
+ * bigramChars: an array for output, at the same format as outwords for getSuggestions.
+ * bigramFreq: an array to output frequencies.
+ * maxWordLength: the maximum size of a word.
+ * maxBigrams: the maximum number of bigrams fitting in the bigramChars array.
+ * maxAlteratives: unused.
+ * This method returns the number of bigrams this word has, for backward compatibility.
+ * Note: this is not the number of bigrams output in the array, which is the number of
+ * bigrams this word has WHOSE first letter also matches the letter the user typed.
+ * TODO: this may not be a sensible thing to do. It makes sense when the bigrams are
+ * used to match the first letter of the second word, but once the user has typed more
+ * and the bigrams are used to boost unigram result scores, it makes little sense to
+ * reduce their scope to the ones that match the first letter.
+ */
int BigramDictionary::getBigrams(unsigned short *prevWord, int prevWordLength, int *codes,
int codesSize, unsigned short *bigramChars, int *bigramFreq, int maxWordLength,
int maxBigrams, int maxAlternatives) {
+ // TODO: remove unused arguments, and refrain from storing stuff in members of this class
+ // TODO: have "in" arguments before "out" ones, and make out args explicit in the name
mBigramFreq = bigramFreq;
mBigramChars = bigramChars;
mInputCodes = codes;
- mInputLength = codesSize;
mMaxBigrams = maxBigrams;
- if (HAS_BIGRAM && IS_LATEST_DICT_VERSION) {
- int pos = mParentDictionary->getBigramPosition(prevWord, prevWordLength);
- if (DEBUG_DICT) {
- LOGI("Pos -> %d", pos);
- }
- if (pos < 0) {
- return 0;
- }
+ const uint8_t* const root = DICT;
+ int pos = BinaryFormat::getTerminalPosition(root, prevWord, prevWordLength);
- int bigramCount = 0;
- int bigramExist = (DICT[pos] & FLAG_BIGRAM_READ);
- if (bigramExist > 0) {
- int nextBigramExist = 1;
- while (nextBigramExist > 0 && bigramCount < maxBigrams) {
- int bigramAddress = getBigramAddress(&pos, true);
- int frequency = (FLAG_BIGRAM_FREQ & DICT[pos]);
- // search for all bigrams and store them
- searchForTerminalNode(bigramAddress, frequency);
- nextBigramExist = (DICT[pos++] & FLAG_BIGRAM_CONTINUED);
- bigramCount++;
- }
- }
-
- return bigramCount;
+ if (NOT_VALID_WORD == pos) return 0;
+ const int flags = BinaryFormat::getFlagsAndForwardPointer(root, &pos);
+ if (0 == (flags & UnigramDictionary::FLAG_HAS_BIGRAMS)) return 0;
+ if (0 == (flags & UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS)) {
+ BinaryFormat::getCharCodeAndForwardPointer(root, &pos);
+ } else {
+ pos = BinaryFormat::skipOtherCharacters(root, pos);
}
- return 0;
-}
+ pos = BinaryFormat::skipChildrenPosition(flags, pos);
+ pos = BinaryFormat::skipFrequency(flags, pos);
+ int bigramFlags;
+ int bigramCount = 0;
+ do {
+ bigramFlags = BinaryFormat::getFlagsAndForwardPointer(root, &pos);
+ uint16_t bigramBuffer[MAX_WORD_LENGTH];
+ const int bigramPos = BinaryFormat::getAttributeAddressAndForwardPointer(root, bigramFlags,
+ &pos);
+ const int length = BinaryFormat::getWordAtAddress(root, bigramPos, MAX_WORD_LENGTH,
+ bigramBuffer);
-void BigramDictionary::searchForTerminalNode(int addressLookingFor, int frequency) {
- // track word with such address and store it in an array
- unsigned short word[MAX_WORD_LENGTH];
-
- int pos;
- int followDownBranchAddress = DICTIONARY_HEADER_SIZE;
- bool found = false;
- char followingChar = ' ';
- int depth = -1;
-
- while(!found) {
- bool followDownAddressSearchStop = false;
- bool firstAddress = true;
- bool haveToSearchAll = true;
-
- if (depth < MAX_WORD_LENGTH && depth >= 0) {
- word[depth] = (unsigned short) followingChar;
+ if (checkFirstCharacter(bigramBuffer)) {
+ const int frequency = UnigramDictionary::MASK_ATTRIBUTE_FREQUENCY & bigramFlags;
+ addWordBigram(bigramBuffer, length, frequency);
}
- pos = followDownBranchAddress; // pos start at count
- int count = DICT[pos] & 0xFF;
- if (DEBUG_DICT) {
- LOGI("count - %d",count);
- }
- pos++;
- for (int i = 0; i < count; i++) {
- // pos at data
- pos++;
- // pos now at flag
- if (!getFirstBitOfByte(&pos)) { // non-terminal
- if (!followDownAddressSearchStop) {
- int addr = getBigramAddress(&pos, false);
- if (addr > addressLookingFor) {
- followDownAddressSearchStop = true;
- if (firstAddress) {
- firstAddress = false;
- haveToSearchAll = true;
- } else if (!haveToSearchAll) {
- break;
- }
- } else {
- followDownBranchAddress = addr;
- followingChar = (char)(0xFF & DICT[pos-1]);
- if (firstAddress) {
- firstAddress = false;
- haveToSearchAll = false;
- }
- }
- }
- pos += 3;
- } else if (getFirstBitOfByte(&pos)) { // terminal
- if (addressLookingFor == (pos-1)) { // found !!
- depth++;
- word[depth] = (0xFF & DICT[pos-1]);
- found = true;
- break;
- }
- if (getSecondBitOfByte(&pos)) { // address + freq (4 byte)
- if (!followDownAddressSearchStop) {
- int addr = getBigramAddress(&pos, false);
- if (addr > addressLookingFor) {
- followDownAddressSearchStop = true;
- if (firstAddress) {
- firstAddress = false;
- haveToSearchAll = true;
- } else if (!haveToSearchAll) {
- break;
- }
- } else {
- followDownBranchAddress = addr;
- followingChar = (char)(0xFF & DICT[pos-1]);
- if (firstAddress) {
- firstAddress = false;
- haveToSearchAll = true;
- }
- }
- }
- pos += 4;
- } else { // freq only (2 byte)
- pos += 2;
- }
-
- // skipping bigram
- int bigramExist = (DICT[pos] & FLAG_BIGRAM_READ);
- if (bigramExist > 0) {
- int nextBigramExist = 1;
- while (nextBigramExist > 0) {
- pos += 3;
- nextBigramExist = (DICT[pos++] & FLAG_BIGRAM_CONTINUED);
- }
- } else {
- pos++;
- }
- }
- }
- depth++;
- if (followDownBranchAddress == 0) {
- if (DEBUG_DICT) {
- LOGI("ERROR!!! Cannot find bigram!!");
- }
- break;
- }
- }
- if (checkFirstCharacter(word)) {
- addWordBigram(word, depth, frequency);
- }
+ ++bigramCount;
+ } while (0 != (UnigramDictionary::FLAG_ATTRIBUTE_HAS_NEXT & bigramFlags));
+ return bigramCount;
}
bool BigramDictionary::checkFirstCharacter(unsigned short *word) {
diff --git a/native/src/binary_format.h b/native/src/binary_format.h
index a946b1e..6f65088 100644
--- a/native/src/binary_format.h
+++ b/native/src/binary_format.h
@@ -50,6 +50,8 @@
int *pos);
static int getTerminalPosition(const uint8_t* const root, const uint16_t* const inWord,
const int length);
+ static int getWordAtAddress(const uint8_t* const root, const int address, const int maxDepth,
+ uint16_t* outWord);
};
inline int BinaryFormat::detectFormat(const uint8_t* const dict) {
@@ -290,6 +292,151 @@
}
}
+// This function searches for a terminal in the dictionary by its address.
+// Due to the fact that words are ordered in the dictionary in a strict breadth-first order,
+// it is possible to check for this with advantageous complexity. For each node, we search
+// for groups with children and compare the children address with the address we look for.
+// When we shoot the address we look for, it means the word we look for is in the children
+// of the previous group. The only tricky part is the fact that if we arrive at the end of a
+// node with the last group's children address still less than what we are searching for, we
+// must descend the last group's children (for example, if the word we are searching for starts
+// with a z, it's the last group of the root node, so all children addresses will be smaller
+// than the address we look for, and we have to descend the z node).
+/* Parameters :
+ * root: the dictionary buffer
+ * address: the byte position of the last chargroup of the word we are searching for (this is
+ * what is stored as the "bigram address" in each bigram)
+ * outword: an array to write the found word, with MAX_WORD_LENGTH size.
+ * Return value : the length of the word, of 0 if the word was not found.
+ */
+inline int BinaryFormat::getWordAtAddress(const uint8_t* const root, const int address,
+ const int maxDepth, uint16_t* outWord) {
+ int pos = 0;
+ int wordPos = 0;
+
+ // One iteration of the outer loop iterates through nodes. As stated above, we will only
+ // traverse nodes that are actually a part of the terminal we are searching, so each time
+ // we enter this loop we are one depth level further than last time.
+ // The only reason we count nodes is because we want to reduce the probability of infinite
+ // looping in case there is a bug. Since we know there is an upper bound to the depth we are
+ // supposed to traverse, it does not hurt to count iterations.
+ for (int loopCount = maxDepth; loopCount > 0; --loopCount) {
+ int lastCandidateGroupPos = 0;
+ // Let's loop through char groups in this node searching for either the terminal
+ // or one of its ascendants.
+ for (int charGroupCount = getGroupCountAndForwardPointer(root, &pos); charGroupCount > 0;
+ --charGroupCount) {
+ const int startPos = pos;
+ const uint8_t flags = getFlagsAndForwardPointer(root, &pos);
+ const int32_t character = getCharCodeAndForwardPointer(root, &pos);
+ if (address == startPos) {
+ // We found the address. Copy the rest of the word in the buffer and return
+ // the length.
+ outWord[wordPos] = character;
+ if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
+ int32_t nextChar = getCharCodeAndForwardPointer(root, &pos);
+ // We count chars in order to avoid infinite loops if the file is broken or
+ // if there is some other bug
+ int charCount = maxDepth;
+ while (-1 != nextChar && --charCount > 0) {
+ outWord[++wordPos] = nextChar;
+ nextChar = getCharCodeAndForwardPointer(root, &pos);
+ }
+ }
+ return ++wordPos;
+ }
+ // We need to skip past this char group, so skip any remaining chars after the
+ // first and possibly the frequency.
+ if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & flags) {
+ pos = skipOtherCharacters(root, pos);
+ }
+ pos = skipFrequency(flags, pos);
+
+ // The fact that this group has children is very important. Since we already know
+ // that this group does not match, if it has no children we know it is irrelevant
+ // to what we are searching for.
+ const bool hasChildren = (UnigramDictionary::FLAG_GROUP_ADDRESS_TYPE_NOADDRESS !=
+ (UnigramDictionary::MASK_GROUP_ADDRESS_TYPE & flags));
+ // We will write in `found' whether we have passed the children address we are
+ // searching for. For example if we search for "beer", the children of b are less
+ // than the address we are searching for and the children of c are greater. When we
+ // come here for c, we realize this is too big, and that we should descend b.
+ bool found;
+ if (hasChildren) {
+ // Here comes the tricky part. First, read the children position.
+ const int childrenPos = readChildrenPosition(root, flags, pos);
+ if (childrenPos > address) {
+ // If the children pos is greater than address, it means the previous chargroup,
+ // which address is stored in lastCandidateGroupPos, was the right one.
+ found = true;
+ } else if (1 >= charGroupCount) {
+ // However if we are on the LAST group of this node, and we have NOT shot the
+ // address we should descend THIS node. So we trick the lastCandidateGroupPos
+ // so that we will descend this node, not the previous one.
+ lastCandidateGroupPos = startPos;
+ found = true;
+ } else {
+ // Else, we should continue looking.
+ found = false;
+ }
+ } else {
+ // Even if we don't have children here, we could still be on the last group of this
+ // node. If this is the case, we should descend the last group that had children,
+ // and their address is already in lastCandidateGroup.
+ found = (1 >= charGroupCount);
+ }
+
+ if (found) {
+ // Okay, we found the group we should descend. Its address is in
+ // the lastCandidateGroupPos variable, so we just re-read it.
+ if (0 != lastCandidateGroupPos) {
+ const uint8_t lastFlags =
+ getFlagsAndForwardPointer(root, &lastCandidateGroupPos);
+ const int32_t lastChar =
+ getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
+ // We copy all the characters in this group to the buffer
+ outWord[wordPos] = lastChar;
+ if (UnigramDictionary::FLAG_HAS_MULTIPLE_CHARS & lastFlags) {
+ int32_t nextChar =
+ getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
+ int charCount = maxDepth;
+ while (-1 != nextChar && --charCount > 0) {
+ outWord[++wordPos] = nextChar;
+ nextChar = getCharCodeAndForwardPointer(root, &lastCandidateGroupPos);
+ }
+ }
+ ++wordPos;
+ // Now we only need to branch to the children address. Skip the frequency if
+ // it's there, read pos, and break to resume the search at pos.
+ lastCandidateGroupPos = skipFrequency(lastFlags, lastCandidateGroupPos);
+ pos = readChildrenPosition(root, lastFlags, lastCandidateGroupPos);
+ break;
+ } else {
+ // Here is a little tricky part: we come here if we found out that all children
+ // addresses in this group are bigger than the address we are searching for.
+ // Should we conclude the word is not in the dictionary? No! It could still be
+ // one of the remaining chargroups in this node, so we have to keep looking in
+ // this node until we find it (or we realize it's not there either, in which
+ // case it's actually not in the dictionary). Pass the end of this group, ready
+ // to start the next one.
+ pos = skipChildrenPosAndAttributes(root, flags, pos);
+ }
+ } else {
+ // If we did not find it, we should record the last children address for the next
+ // iteration.
+ if (hasChildren) lastCandidateGroupPos = startPos;
+ // Now skip the end of this group (children pos and the attributes if any) so that
+ // our pos is after the end of this char group, at the start of the next one.
+ pos = skipChildrenPosAndAttributes(root, flags, pos);
+ }
+
+ }
+ }
+ // If we have looked through all the chargroups and found no match, the address is
+ // not the address of a terminal in this dictionary.
+ return 0;
+}
+
} // namespace latinime
#endif // LATINIME_BINARY_FORMAT_H
diff --git a/native/src/dictionary.cpp b/native/src/dictionary.cpp
index 9e32ee8..a49769b 100644
--- a/native/src/dictionary.cpp
+++ b/native/src/dictionary.cpp
@@ -57,12 +57,4 @@
return mUnigramDictionary->isValidWord(word, length);
}
-int Dictionary::getBigramPosition(unsigned short *word, int length) {
- if (IS_LATEST_DICT_VERSION) {
- return mUnigramDictionary->getBigramPosition(DICTIONARY_HEADER_SIZE, word, 0, length);
- } else {
- return mUnigramDictionary->getBigramPosition(0, word, 0, length);
- }
-}
-
} // namespace latinime
diff --git a/native/src/dictionary.h b/native/src/dictionary.h
index 73e03d8..d5de008 100644
--- a/native/src/dictionary.h
+++ b/native/src/dictionary.h
@@ -64,8 +64,6 @@
const int pos, unsigned short *c, int *childrenPosition,
bool *terminal, int *freq);
static inline unsigned short toBaseLowerCase(unsigned short c);
- // TODO: delete this
- int getBigramPosition(unsigned short *word, int length);
private:
bool hasBigram();