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Fixes and more documentation
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1 changed files with 25 additions and 12 deletions
37
correct.c
37
correct.c
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@ -33,7 +33,7 @@
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*
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* A little about how it works, and probability theory:
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*
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* When given an identifier (which we will denote I), we're essentially
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* When given an identifier (which we will denote I), we're essentially
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* just trying to choose the most likely correction for that identifier.
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* (the actual "correction" can very well be the identifier itself).
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* There is actually no way to know for sure that certian identifers
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@ -44,9 +44,20 @@
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* out of all possible corrections that maximizes the probability of C
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* for the original identifer I.
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*
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* Bayes' Therom suggests something of the following:
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* Thankfully there exists some theroies for probalistic interpretations
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* of data. Since we're operating on two distictive intepretations, the
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* transposition from I to C. We need something that can express how much
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* degree of I should rationally change to become C. this is called the
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* Bayesian interpretation. You can read more about it from here:
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* http://www.celiagreen.com/charlesmccreery/statistics/bayestutorial.pdf
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* (which is probably the only good online documentation for bayes theroy
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* no lie. Everything else just sucks ..)
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*
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* Bayes' Thereom suggests something like the following:
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* AC P(I|C) P(C) / P(I)
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* Since P(I) is the same for every possibly I, we can ignore it giving
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*
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* However since P(I) is the same for every possibility of I, we can
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* complete ignore it giving just:
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* AC P(I|C) P(C)
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*
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* This greatly helps visualize how the parts of the expression are performed
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@ -78,7 +89,7 @@
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*
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* A little information on additional algorithms used:
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*
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* Initially when I implemented this corrector, it was very slow.
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* Initially when I implemented this corrector, it was very slow.
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* Need I remind you this is essentially a brute force attack on strings,
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* and since every transformation requires dynamic memory allocations,
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* you can easily imagine where most of the runtime conflated. Yes
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@ -87,7 +98,7 @@
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* shock to me. A forward allocator (or as some call it a bump-point
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* allocator, or just a memory pool) was implemented. To combat this.
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*
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* But of course even other factors were making it slow. Initially
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* But of course even other factors were making it slow. Initially
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* this used a hashtable. And hashtables have a good constant lookup
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* time complexity. But the problem wasn't in the hashtable, it was
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* in the hashing (despite having one of the fastest hash functions
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@ -99,18 +110,19 @@
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*
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* Future Work (If we really need it)
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*
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* Currently we can only distinguishes one source of error in the
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* Currently we can only distinguishes one source of error in the
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* language model we use. This could become an issue for identifiers
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* that have close colliding rates, e.g colate->coat yields collate.
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*
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* Currently the error model has been fairly trivial, the smaller the
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* Currently the error model has been fairly trivial, the smaller the
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* edit distance the smaller the error. This usually causes some un-
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* expected problems. e.g reciet->recite yields recipt. For QuakeC
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* this could become a problem when lots of identifiers are involved.
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*
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* Our control mechanisim could use a limit, i.e limit the number of
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* Our control mechanisim could use a limit, i.e limit the number of
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* sets of edits for distance X. This would also increase execution
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* speed considerably.
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* speed considerably.
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*
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*/
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@ -163,12 +175,12 @@ static GMQCC_INLINE char *correct_pool_claim(const char *data) {
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}
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/*
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* A fast space efficent trie for a disctonary of identifiers. This is
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* A fast space efficent trie for a dictionary of identifiers. This is
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* faster than a hashtable for one reason. A hashtable itself may have
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* fast constant lookup time, but the hash itself must be very fast. We
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* have one of the fastest hash functions for strings, but if you do a
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* lost of hashing (which we do, almost 3 million hashes per identifier)
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* a hashtable becomes slow. Very Very Slow.
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* a hashtable becomes slow.
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*/
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correct_trie_t* correct_trie_new() {
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correct_trie_t *t = (correct_trie_t*)mem_a(sizeof(correct_trie_t));
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@ -440,7 +452,8 @@ static char **correct_known(correct_trie_t* table, char **array, size_t rows, si
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end = correct_edit(array[itr]);
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row = correct_size(array[itr]);
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for (; jtr < row; jtr++) {
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/* removing jtr=0 here speeds it up by 100ms O_o */
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for (jtr = 0; jtr < row; jtr++) {
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if (correct_find(table, end[jtr]) && !correct_exist(res, len, end[jtr])) {
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res = correct_known_resize(res, &nxt, len+1);
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res[len++] = end[jtr];
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