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Use a 2D array for memoization, gives clearer code

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Kovid Goyal 2014-03-05 08:44:02 +05:30
parent ed45f1a6aa
commit 4398dda15f
1 changed files with 24 additions and 9 deletions
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33
src/calibre/gui2/tweak_book/matcher.c
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@ -37,7 +37,7 @@ typedef struct {
UChar *needle; UChar *needle;
int32_t needle_len; int32_t needle_len;
double max_score_per_char; double max_score_per_char;
double *memo; double **memo;
UChar *level1; UChar *level1;
UChar *level2; UChar *level2;
UChar *level3; UChar *level3;
@ -58,7 +58,7 @@ static double recursive_match(MatchInfo *m, int32_t haystack_idx, int32_t needle
bool found; bool found;
// do we have a memoized result we can return? // do we have a memoized result we can return?
memoized = m->memo[needle_idx * m->needle_len + haystack_idx]; memoized = m->memo[needle_idx][haystack_idx];
if (memoized != DBL_MAX) if (memoized != DBL_MAX)
return memoized; return memoized;
@ -125,15 +125,29 @@ static double recursive_match(MatchInfo *m, int32_t haystack_idx, int32_t needle
score = score > seen_score ? score : seen_score; score = score > seen_score ? score : seen_score;
memoize: memoize:
m->memo[needle_idx * m->needle_len + haystack_idx] = score; m->memo[needle_idx][haystack_idx] = score;
return score; return score;
} }
static double** alloc_memo(size_t rows, size_t cols) {
double **array, *data; /* Declare this first so we can use it with sizeof. */
size_t i;
const size_t row_pointers_bytes = rows * sizeof(*array);
const size_t row_elements_bytes = cols * sizeof(**array);
array = malloc(row_pointers_bytes + rows * row_elements_bytes);
if (array != NULL) {
data = (double*)(array + rows);
for(i = 0; i < rows; i++) array[i] = data + i * cols;
}
return array;
}
static bool match(UChar **items, int32_t *item_lengths, uint32_t item_count, UChar *needle, int32_t needle_len, Match *match_results, UChar *level1, UChar *level2, UChar *level3) { static bool match(UChar **items, int32_t *item_lengths, uint32_t item_count, UChar *needle, int32_t needle_len, Match *match_results, UChar *level1, UChar *level2, UChar *level3) {
uint32_t i = 0, maxhl = 0, n = 0; uint32_t i = 0, maxhl = 0;
int32_t r = 0, c = 0;
MatchInfo *matches = NULL; MatchInfo *matches = NULL;
bool ok = FALSE; bool ok = FALSE;
double *memo = NULL; double **memo = NULL;
if (needle_len == 0) { if (needle_len == 0) {
for (i = 0; i < item_count; i++) match_results[i].score = 0.0; for (i = 0; i < item_count; i++) match_results[i].score = 0.0;
@ -155,13 +169,14 @@ static bool match(UChar **items, int32_t *item_lengths, uint32_t item_count, UCh
matches[i].level3 = level3; matches[i].level3 = level3;
maxhl = MAX(maxhl, matches[i].haystack_len); maxhl = MAX(maxhl, matches[i].haystack_len);
} }
maxhl *= needle_len;
memo = (double*)calloc(maxhl, sizeof(double)); memo = alloc_memo(needle_len, maxhl);
if (memo == NULL) goto end; if (memo == NULL) {PyErr_NoMemory(); goto end;}
for (i = 0; i < item_count; i++) { for (i = 0; i < item_count; i++) {
for (n = 0; n < maxhl; n++) memo[n] = DBL_MAX; for (r = 0; r < needle_len; r++) {
for (c = 0; c < maxhl; c++) memo[r][c] = DBL_MAX;
}
matches[i].memo = memo; matches[i].memo = memo;
match_results[i].score = recursive_match(&matches[i], 0, 0, 0, 0.0); match_results[i].score = recursive_match(&matches[i], 0, 0, 0, 0.0);
} }