--- /dev/null
+/*
+ * Copyright (C) 2012, 2013
+ * Dale Weiler
+ * Wolfgang Bumiller
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is furnished to do
+ * so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include <string.h>
+#include "gmqcc.h"
+
+/*
+ * This is a very clever method for correcting mistakes in QuakeC code
+ * most notably when invalid identifiers are used or inproper assignments;
+ * we can proprly lookup in multiple dictonaries (depening on the rules
+ * of what the task is trying to acomplish) to find the best possible
+ * match.
+ *
+ *
+ * A little about how it works, and probability theory:
+ *
+ * When given an identifier (which we will denote I), we're essentially
+ * just trying to choose the most likely correction for that identifier.
+ * (the actual "correction" can very well be the identifier itself).
+ * There is actually no way to know for sure that certian identifers
+ * such as "lates", need to be corrected to "late" or "latest" or any
+ * other permutations that look lexically the same. This is why we
+ * must advocate the usage of probabilities. This means that instead of
+ * just guessing, instead we're trying to find the correction for C,
+ * out of all possible corrections that maximizes the probability of C
+ * for the original identifer I.
+ *
+ * Thankfully there exists some theroies for probalistic interpretations
+ * of data. Since we're operating on two distictive intepretations, the
+ * transposition from I to C. We need something that can express how much
+ * degree of I should rationally change to become C. this is called the
+ * Bayesian interpretation. You can read more about it from here:
+ * http://www.celiagreen.com/charlesmccreery/statistics/bayestutorial.pdf
+ * (which is probably the only good online documentation for bayes theroy
+ * no lie. Everything else just sucks ..)
+ *
+ * Bayes' Thereom suggests something like the following:
+ * AC P(I|C) P(C) / P(I)
+ *
+ * However since P(I) is the same for every possibility of I, we can
+ * completley ignore it giving just:
+ * AC P(I|C) P(C)
+ *
+ * This greatly helps visualize how the parts of the expression are performed
+ * there is essentially three, from right to left we perform the following:
+ *
+ * 1: P(C), the probability that a proposed correction C will stand on its
+ * own. This is called the language model.
+ *
+ * 2: P(I|C), the probability that I would be used, when the programmer
+ * really meant C. This is the error model.
+ *
+ * 3: AC, the control mechanisim, an enumerator if you will, one that
+ * enumerates all feasible values of C, to determine the one that
+ * gives the greatest probability score.
+ *
+ * In reality the requirement for a more complex expression involving
+ * two seperate models is considerably a waste. But one must recognize
+ * that P(C|I) is already conflating two factors. It's just much simpler
+ * to seperate the two models and deal with them explicitaly. To properly
+ * estimate P(C|I) you have to consider both the probability of C and
+ * probability of the transposition from C to I. It's simply much more
+ * cleaner, and direct to seperate the two factors.
+ *
+ * Research tells us that 80% to 95% of all spelling errors have an edit
+ * distance no greater than one. Knowing this we can optimize for most
+ * cases of mistakes without taking a performance hit. Which is what we
+ * base longer edit distances off of. Opposed to the original method of
+ * I had concieved of checking everything.
+ *
+ * A little information on additional algorithms used:
+ *
+ * Initially when I implemented this corrector, it was very slow.
+ * Need I remind you this is essentially a brute force attack on strings,
+ * and since every transformation requires dynamic memory allocations,
+ * you can easily imagine where most of the runtime conflated. Yes
+ * It went right to malloc. More than THREE MILLION malloc calls are
+ * performed for an identifier about 16 bytes long. This was such a
+ * shock to me. A forward allocator (or as some call it a bump-point
+ * allocator, or just a memory pool) was implemented. To combat this.
+ *
+ * But of course even other factors were making it slow. Initially
+ * this used a hashtable. And hashtables have a good constant lookup
+ * time complexity. But the problem wasn't in the hashtable, it was
+ * in the hashing (despite having one of the fastest hash functions
+ * known). Remember those 3 million mallocs? Well for every malloc
+ * there is also a hash. After 3 million hashes .. you start to get
+ * very slow. To combat this I had suggested burst tries to Blub.
+ * The next day he had implemented them. Sure enough this brought
+ * down the runtime by a factor > 100%
+ *
+ * The trie initially was designed to work on all strings, but later it
+ * became aparent that not only was this not a requirement. It was also
+ * slowing down get/sets' for the trie. To fully understand, only
+ * correct_alpha needs to be understood by the trie system, knowing this
+ * We can combat the slowness using a very clever but evil optimization.
+ * By Setting a fixed sized amount of branches for the trie using a
+ * char-to-index map into the branches. We've complelty made the trie
+ * accesses entierly constant in lookup time. No really, a lookup is
+ * literally trie[str[0]] [str[1]] [2] .... .value.
+ *
+ *
+ * Future Work (If we really need it)
+ *
+ * Currently we can only distinguish one source of error in the
+ * language model we use. This could become an issue for identifiers
+ * that have close colliding rates, e.g colate->coat yields collate.
+ *
+ * Currently the error model has been fairly trivial, the smaller the
+ * edit distance the smaller the error. This usually causes some un-
+ * expected problems. e.g reciet->recite yields recipt. For QuakeC
+ * this could become a problem when lots of identifiers are involved.
+ */
+
+
+#define CORRECT_POOL_SIZE (128*1024*1024)
+/*
+ * A forward allcator for the corrector. This corrector requires a lot
+ * of allocations. This forward allocator combats all those allocations
+ * and speeds us up a little. It also saves us space in a way since each
+ * allocation isn't wasting a little header space for when NOTRACK isn't
+ * defined.
+ */
+static unsigned char **correct_pool_data = NULL;
+static unsigned char *correct_pool_this = NULL;
+static size_t correct_pool_addr = 0;
+
+static GMQCC_INLINE void correct_pool_new(void) {
+ correct_pool_addr = 0;
+ correct_pool_this = (unsigned char *)mem_a(CORRECT_POOL_SIZE);
+
+ vec_push(correct_pool_data, correct_pool_this);
+}
+
+static GMQCC_INLINE void *correct_pool_alloc(size_t bytes) {
+ void *data;
+ if (correct_pool_addr + bytes>= CORRECT_POOL_SIZE)
+ correct_pool_new();
+
+ data = (void*)correct_pool_this;
+ correct_pool_this += bytes;
+ correct_pool_addr += bytes;
+ return data;
+}
+
+static GMQCC_INLINE void correct_pool_delete(void) {
+ size_t i;
+ for (i = 0; i < vec_size(correct_pool_data); ++i)
+ mem_d(correct_pool_data[i]);
+
+ correct_pool_data = NULL;
+ correct_pool_this = NULL;
+ correct_pool_addr = 0;
+}
+
+
+static GMQCC_INLINE char *correct_pool_claim(const char *data) {
+ char *claim = util_strdup(data);
+ return claim;
+}
+
+/*
+ * _ is valid in identifiers. I've yet to implement numerics however
+ * because they're only valid after the first character is of a _, or
+ * alpha character.
+ */
+static const char correct_alpha[] = "abcdefghijklmnopqrstuvwxyz"
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+ "_"; /* TODO: Numbers ... */
+
+static const size_t correct_alpha_index[0x80] = {
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+ 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 52,
+ 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+ 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 0, 0, 0, 0, 0
+};
+
+/*
+ * A fast space efficent trie for a dictionary of identifiers. This is
+ * faster than a hashtable for one reason. A hashtable itself may have
+ * fast constant lookup time, but the hash itself must be very fast. We
+ * have one of the fastest hash functions for strings, but if you do a
+ * lost of hashing (which we do, almost 3 million hashes per identifier)
+ * a hashtable becomes slow.
+ */
+correct_trie_t* correct_trie_new() {
+ correct_trie_t *t = (correct_trie_t*)mem_a(sizeof(correct_trie_t));
+ t->value = NULL;
+ t->entries = NULL;
+ return t;
+}
+
+static GMQCC_INLINE void correct_trie_del_sub(correct_trie_t *t) {
+ size_t i;
+ if (!t->entries)
+ return;
+ for (i = 0; i < sizeof(correct_alpha)-1; ++i) {
+ correct_trie_del_sub(&t->entries[i]);
+ }
+ mem_d(t->entries);
+}
+
+static GMQCC_INLINE void correct_trie_del(correct_trie_t *t) {
+ size_t i;
+ if (t->entries) {
+ for (i = 0; i < sizeof(correct_alpha)-1; ++i)
+ correct_trie_del_sub(&t->entries[i]);
+ mem_d(t->entries);
+ }
+ mem_d(t);
+}
+
+static GMQCC_INLINE void* correct_trie_get(const correct_trie_t *t, const char *key) {
+ const unsigned char *data = (const unsigned char*)key;
+
+ while (*data) {
+ if (!t->entries)
+ return NULL;
+ t = t->entries + correct_alpha_index[*data];
+ ++data;
+ }
+ return t->value;
+}
+
+static GMQCC_INLINE void correct_trie_set(correct_trie_t *t, const char *key, void * const value) {
+ const unsigned char *data = (const unsigned char*)key;
+ while (*data) {
+ if (!t->entries) {
+ t->entries = (correct_trie_t*)mem_a(sizeof(correct_trie_t)*(sizeof(correct_alpha)-1));
+ memset(t->entries, 0, sizeof(correct_trie_t)*(sizeof(correct_alpha)-1));
+ }
+ t = t->entries + correct_alpha_index[*data];
+ ++data;
+ }
+ t->value = value;
+}
+
+
+/*
+ * Implementation of the corrector algorithm commences. A very efficent
+ * brute-force attack (thanks to tries and mempool :-)).
+ */
+static GMQCC_INLINE size_t *correct_find(correct_trie_t *table, const char *word) {
+ return (size_t*)correct_trie_get(table, word);
+}
+
+static GMQCC_INLINE bool correct_update(correct_trie_t* *table, const char *word) {
+ size_t *data = correct_find(*table, word);
+ if (!data)
+ return false;
+
+ (*data)++;
+ return true;
+}
+
+void correct_add(correct_trie_t* table, size_t ***size, const char *ident) {
+ size_t *data = NULL;
+ const char *add = ident;
+
+ if (!correct_update(&table, add)) {
+ data = (size_t*)mem_a(sizeof(size_t));
+ *data = 1;
+
+ vec_push((*size), data);
+ correct_trie_set(table, add, data);
+ }
+}
+
+void correct_del(correct_trie_t* dictonary, size_t **data) {
+ size_t i;
+ const size_t vs = vec_size(data);
+
+ for (i = 0; i < vs; i++)
+ mem_d(data[i]);
+
+ vec_free(data);
+ correct_trie_del(dictonary);
+}
+
+/*
+ * correcting logic for the following forms of transformations:
+ * 1) deletion
+ * 2) transposition
+ * 3) alteration
+ * 4) insertion
+ *
+ * These functions could take an additional size_t **size paramater
+ * and store back the results of their new length in an array that
+ * is the same as **array for the memcmp in correct_exists. I'm just
+ * not able to figure out how to do that just yet. As my brain is
+ * not in the mood to figure out that logic. This is a reminder to
+ * do it, or for someone else to :-) correct_edit however would also
+ * need to take a size_t ** to carry it along (would all the argument
+ * overhead be worth it?)
+ */
+static GMQCC_INLINE size_t correct_deletion(const char *ident, char **array) {
+ size_t itr = 0;
+ const size_t len = strlen(ident);
+
+ for (; itr < len; itr++) {
+ char *a = (char*)correct_pool_alloc(len+1);
+ memcpy(a, ident, itr);
+ memcpy(a + itr, ident + itr + 1, len - itr);
+ array[itr] = a;
+ }
+
+ return itr;
+}
+
+static GMQCC_INLINE size_t correct_transposition(const char *ident, char **array) {
+ size_t itr = 0;
+ const size_t len = strlen(ident);
+
+ for (; itr < len - 1; itr++) {
+ char tmp;
+ char *a = (char*)correct_pool_alloc(len+1);
+ memcpy(a, ident, len+1);
+ tmp = a[itr];
+ a[itr ] = a[itr+1];
+ a[itr+1] = tmp;
+ array[itr] = a;
+ }
+
+ return itr;
+}
+
+static GMQCC_INLINE size_t correct_alteration(const char *ident, char **array) {
+ size_t itr = 0;
+ size_t jtr = 0;
+ size_t ktr = 0;
+ const size_t len = strlen(ident);
+
+ for (; itr < len; itr++) {
+ for (jtr = 0; jtr < sizeof(correct_alpha)-1; jtr++, ktr++) {
+ char *a = (char*)correct_pool_alloc(len+1);
+ memcpy(a, ident, len+1);
+ a[itr] = correct_alpha[jtr];
+ array[ktr] = a;
+ }
+ }
+
+ return ktr;
+}
+
+static GMQCC_INLINE size_t correct_insertion(const char *ident, char **array) {
+ size_t itr = 0;
+ size_t jtr = 0;
+ const size_t len = strlen(ident);
+
+ for (; itr <= len; itr++) {
+ for (jtr = 0; jtr < sizeof(correct_alpha)-1; jtr++) {
+ char *a = (char*)correct_pool_alloc(len+2);
+ memcpy(a, ident, itr);
+ memcpy(a + itr + 1, ident + itr, len - itr + 1);
+ a[itr] = correct_alpha[jtr];
+ array[itr * (sizeof(correct_alpha)-1) + jtr] = a;
+ }
+ }
+
+ return (len+1)*(sizeof(correct_alpha)-1);
+}
+
+static GMQCC_INLINE size_t correct_size(const char *ident) {
+ /*
+ * deletion = len
+ * transposition = len - 1
+ * alteration = len * sizeof(correct_alpha)
+ * insertion = (len + 1) * sizeof(correct_alpha)
+ */
+
+ register size_t len = strlen(ident);
+ return (len) + (len - 1) + (len * (sizeof(correct_alpha)-1)) + ((len + 1) * (sizeof(correct_alpha)-1));
+}
+
+static GMQCC_INLINE char **correct_edit(const char *ident, size_t **lens) {
+ size_t next;
+ size_t size = correct_size(ident);
+ char **find = (char**)correct_pool_alloc(size * sizeof(char*));
+
+ if (!find || !(*lens = (size_t*)correct_pool_alloc(size * sizeof(size_t))))
+ return NULL;
+
+ next = correct_deletion (ident, find);
+ next += correct_transposition(ident, find+next);
+ next += correct_alteration (ident, find+next);
+ /*****/ correct_insertion (ident, find+next);
+
+ /* precompute lengths */
+ for (next = 0; next < size; next++)
+ (*lens)[next] = strlen(find[next]);
+
+ return find;
+}
+
+static GMQCC_INLINE int correct_exist(char **array, register size_t *sizes, size_t rows, char *ident, register size_t len) {
+ size_t itr;
+ for (itr = 0; itr < rows; itr++) {
+ /*
+ * We can save tons of calls to memcmp if we simply ignore comparisions
+ * that we know cannot contain the same length.
+ */
+ if (sizes[itr] == len && !memcmp(array[itr], ident, len))
+ return 1;
+ }
+
+ return 0;
+}
+
+static GMQCC_INLINE char **correct_known_resize(char **res, size_t *allocated, size_t size) {
+ size_t oldallocated = *allocated;
+ char **out;
+ if (size < oldallocated)
+ return res;
+
+ out = (char**)correct_pool_alloc(sizeof(*res) * oldallocated + 32);
+ memcpy(out, res, sizeof(*res) * oldallocated);
+
+ *allocated += 32;
+ return out;
+}
+
+static char **correct_known(correction_t *corr, correct_trie_t* table, char **array, size_t rows, size_t *next) {
+ size_t itr = 0;
+ size_t jtr = 0;
+ size_t len = 0;
+ size_t row = 0;
+ size_t nxt = 8;
+ char **res = (char**)correct_pool_alloc(sizeof(char *) * nxt);
+ char **end = NULL;
+ size_t *bit = NULL;
+
+ for (; itr < rows; itr++) {
+ if (!array[itr][0])
+ continue;
+ if (vec_size(corr->edits) > itr+1) {
+ end = corr->edits[itr+1];
+ bit = corr->lens [itr+1];
+ } else {
+ end = correct_edit(array[itr], &bit);
+ vec_push(corr->edits, end);
+ vec_push(corr->lens, bit);
+ }
+ row = correct_size(array[itr]);
+
+ for (jtr = 0; jtr < row; jtr++) {
+ if (correct_find(table, end[jtr]) && !correct_exist(res, bit, len, end[jtr], bit[jtr])) {
+ res = correct_known_resize(res, &nxt, len+1);
+ res[len++] = end[jtr];
+ }
+ }
+ }
+
+ *next = len;
+ return res;
+}
+
+static GMQCC_INLINE char *correct_maximum(correct_trie_t* table, char **array, size_t rows) {
+ char *str = NULL;
+ size_t *itm = NULL;
+ size_t itr = 0;
+ size_t top = 0;
+
+ for (; itr < rows; itr++) {
+ if ((itm = correct_find(table, array[itr])) && (*itm > top)) {
+ top = *itm;
+ str = array[itr];
+ }
+ }
+
+ return str;
+}
+
+/*
+ * This is the exposed interface:
+ * takes a table for the dictonary a vector of sizes (used for internal
+ * probability calculation), and an identifier to "correct".
+ */
+void correct_init(correction_t *c)
+{
+ correct_pool_new();
+ c->edits = NULL;
+ c->lens = NULL;
+}
+
+void correct_free(correction_t *c)
+{
+ vec_free(c->edits);
+ vec_free(c->lens);
+ correct_pool_delete();
+}
+
+char *correct_str(correction_t *corr, correct_trie_t* table, const char *ident) {
+ char **e1 = NULL;
+ char **e2 = NULL;
+ char *e1ident = NULL;
+ char *e2ident = NULL;
+ size_t e1rows = 0;
+ size_t e2rows = 0;
+ size_t *bits = NULL;
+
+ /* needs to be allocated for free later */
+ if (correct_find(table, ident))
+ return correct_pool_claim(ident);
+
+ if ((e1rows = correct_size(ident))) {
+ if (vec_size(corr->edits) > 0)
+ e1 = corr->edits[0];
+ else {
+ e1 = correct_edit(ident, &bits);
+ vec_push(corr->edits, e1);
+ vec_push(corr->lens, bits);
+ }
+
+ if ((e1ident = correct_maximum(table, e1, e1rows)))
+ return correct_pool_claim(e1ident);
+ }
+
+ e2 = correct_known(corr, table, e1, e1rows, &e2rows);
+ if (e2rows && ((e2ident = correct_maximum(table, e2, e2rows))))
+ return correct_pool_claim(e2ident);
+
+
+ return util_strdup(ident);
+}
projects / voretournament / voretournament.git / blobdiff