GitHub/gf-core
1
0
Fork 1
mirror of https://github.com/GrammaticalFramework/gf-core.git synced 2026-04-11 05:49:31 -06:00
Code Issues Packages Projects Releases Wiki Activity

Take a step back and do bottom up prediction only when needed. This solves the problem that some sentences were impossible to parse.

Browse Source
This commit is contained in:
krangelov
2020-11-17 10:26:00 +01:00
parent 7dc6717b5e
commit d4ccd2848c
1 changed files with 138 additions and 196 deletions
Download Patch File Download Diff File Expand all files Collapse all files

334
src/runtime/c/pgf/parser.c
View File

@@ -61,6 +61,14 @@ typedef struct {
typedef enum { BIND_NONE, BIND_HARD, BIND_SOFT } BIND_TYPE;
typedef struct {
PgfProductionIdx* idx;
size_t offset;
size_t sym_idx;
} PgfLexiconIdxEntry;
typedef GuBuf PgfLexiconIdx;
struct PgfParseState {
PgfParseState* next;
@@ -74,6 +82,8 @@ struct PgfParseState {
size_t end_offset;
prob_t viterbi_prob;
PgfLexiconIdx* lexicon_idx;
};
typedef struct PgfAnswers {
@@ -686,16 +696,6 @@ pgf_result_production(PgfParsing* ps,
static void
pgf_parsing_complete(PgfParsing* ps, PgfItem* item, PgfExprProb *ep);
static void
pgf_parsing_push_item(PgfParseState* state, PgfItem* item)
{
if (gu_buf_length(state->agenda) == 0) {
state->viterbi_prob =
item->inside_prob+item->conts->outside_prob;
}
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
}
static void
pgf_parsing_push_production(PgfParsing* ps, PgfParseState* state,
PgfItemConts* conts, PgfProduction prod)
@@ -727,7 +727,7 @@ pgf_parsing_combine(PgfParsing* ps,
}
pgf_item_advance(item, ps->pool);
pgf_parsing_push_item(before, item);
gu_buf_heap_push(before->agenda, pgf_item_prob_order, &item);
}
static PgfProduction
@@ -898,9 +898,65 @@ pgf_parsing_complete(PgfParsing* ps, PgfItem* item, PgfExprProb *ep)
}
}
PGF_INTERNAL_DECL int
pgf_symbols_cmp(PgfCohortSpot* spot,
PgfSymbols* syms, size_t* sym_idx,
bool case_sensitive);
static void
pgf_parsing_lookahead(PgfParsing *ps, PgfParseState* state,
int i, int j, ptrdiff_t min, ptrdiff_t max)
{
// This is a variation of a binary search algorithm which
// can retrieve all prefixes of a string with minimal
// comparisons, i.e. there is no need to lookup every
// prefix separately.
while (i <= j) {
int k = (i+j) / 2;
PgfSequence* seq = gu_seq_index(ps->concr->sequences, PgfSequence, k);
PgfCohortSpot start = {0, ps->sentence + state->end_offset};
PgfCohortSpot current = start;
size_t sym_idx = 0;
int cmp = pgf_symbols_cmp(&current, seq->syms, &sym_idx, ps->case_sensitive);
if (cmp < 0) {
j = k-1;
} else if (cmp > 0) {
ptrdiff_t len = current.ptr - start.ptr;
if (min <= len)
pgf_parsing_lookahead(ps, state, i, k-1, min, len);
if (len+1 <= max)
pgf_parsing_lookahead(ps, state, k+1, j, len+1, max);
break;
} else {
ptrdiff_t len = current.ptr - start.ptr;
if (min <= len-1)
pgf_parsing_lookahead(ps, state, i, k-1, min, len-1);
if (seq->idx != NULL) {
PgfLexiconIdxEntry* entry = gu_buf_extend(state->lexicon_idx);
entry->idx = seq->idx;
entry->offset = (size_t) (current.ptr - ps->sentence);
entry->sym_idx = sym_idx;
}
if (len+1 <= max)
pgf_parsing_lookahead(ps, state, k+1, j, len+1, max);
break;
}
}
}
static PgfParseState*
pgf_new_parse_state(PgfParsing* ps, size_t start_offset,
BIND_TYPE bind_type)
BIND_TYPE bind_type,
prob_t viterbi_prob)
{
PgfParseState** pstate;
if (ps->before == NULL && start_offset == 0)
@@ -953,172 +1009,36 @@ pgf_new_parse_state(PgfParsing* ps, size_t start_offset,
(start_offset == end_offset);
state->start_offset = start_offset;
state->end_offset = end_offset;
state->viterbi_prob = 0;
state->viterbi_prob = viterbi_prob;
state->lexicon_idx =
gu_new_buf(PgfLexiconIdxEntry, ps->pool);
if (ps->before == NULL && start_offset == 0)
state->needs_bind = false;
if (gu_seq_length(ps->concr->sequences) > 0) {
// Add epsilon lexical rules to the bottom up index
PgfSequence* seq = gu_seq_index(ps->concr->sequences, PgfSequence, 0);
if (gu_seq_length(seq->syms) == 0 && seq->idx != NULL) {
PgfLexiconIdxEntry* entry = gu_buf_extend(state->lexicon_idx);
entry->idx = seq->idx;
entry->offset = state->start_offset;
entry->sym_idx= 0;
}
// Add non-epsilon lexical rules to the bottom up index
if (!state->needs_bind) {
pgf_parsing_lookahead(ps, state,
0, gu_seq_length(ps->concr->sequences)-1,
1, strlen(ps->sentence)-state->end_offset);
}
}
*pstate = state;
return state;
}
PGF_INTERNAL_DECL int
pgf_symbols_cmp(PgfCohortSpot* spot,
PgfSymbols* syms, size_t* sym_idx,
bool case_sensitive);
static bool
pgf_parsing_scan_helper(PgfParsing *ps, PgfParseState* state,
int i, int j, ptrdiff_t min, ptrdiff_t max)
{
// This is a variation of a binary search algorithm which
// can retrieve all prefixes of a string with minimal
// comparisons, i.e. there is no need to lookup every
// prefix separately.
bool found = false;
while (i <= j) {
int k = (i+j) / 2;
PgfSequence* seq = gu_seq_index(ps->concr->sequences, PgfSequence, k);
PgfCohortSpot start = {0, ps->sentence+state->end_offset};
PgfCohortSpot current = start;
size_t sym_idx = 0;
int cmp = pgf_symbols_cmp(&current, seq->syms, &sym_idx, ps->case_sensitive);
if (cmp < 0) {
j = k-1;
} else if (cmp > 0) {
ptrdiff_t len = current.ptr - start.ptr;
if (min <= len)
if (pgf_parsing_scan_helper(ps, state, i, k-1, min, len))
found = true;
if (len+1 <= max)
if (pgf_parsing_scan_helper(ps, state, k+1, j, len+1, max))
found = true;
break;
} else {
ptrdiff_t len = current.ptr - start.ptr;
if (min <= len)
if (pgf_parsing_scan_helper(ps, state, i, k-1, min, len))
found = true;
// Here we do bottom-up prediction for all lexical categories.
// The epsilon productions will be predicted in top-down
// fashion while parsing.
if (seq->idx != NULL && len > 0) {
found = true;
// A new state will mark the end of the current match
PgfParseState* new_state =
pgf_new_parse_state(ps, (size_t) (current.ptr - ps->sentence), BIND_NONE);
// Bottom-up prediction for lexical rules
size_t n_entries = gu_buf_length(seq->idx);
for (size_t i = 0; i < n_entries; i++) {
PgfProductionIdxEntry* entry =
gu_buf_index(seq->idx, PgfProductionIdxEntry, i);
PgfItemConts* conts =
pgf_parsing_get_conts(state,
entry->ccat, entry->lin_idx,
ps->pool);
// Create the new category if it doesn't exist yet
PgfCCat* tmp_ccat = pgf_parsing_get_completed(new_state, conts);
PgfCCat* ccat = tmp_ccat;
if (ccat == NULL) {
ccat = pgf_parsing_create_completed(ps, new_state, conts, INFINITY);
}
// Add the production
if (ccat->prods == NULL || ccat->n_synprods >= gu_seq_length(ccat->prods)) {
ccat->prods = gu_realloc_seq(ccat->prods, PgfProduction, ccat->n_synprods+1);
}
GuVariantInfo i;
i.tag = PGF_PRODUCTION_APPLY;
i.data = entry->papp;
PgfProduction prod = gu_variant_close(i);
gu_seq_set(ccat->prods, PgfProduction, ccat->n_synprods++, prod);
// Update the category's probability to be minimum
if (ccat->viterbi_prob > entry->papp->fun->ep->prob)
ccat->viterbi_prob = entry->papp->fun->ep->prob;
#ifdef PGF_PARSER_DEBUG
GuPool* tmp_pool = gu_new_pool();
GuOut* out = gu_file_out(stderr, tmp_pool);
GuExn* err = gu_exn(tmp_pool);
if (tmp_ccat == NULL) {
gu_printf(out, err, "[");
pgf_print_range(state, new_state, out, err);
gu_puts("; ", out, err);
pgf_print_fid(conts->ccat->fid, out, err);
gu_printf(out, err, "; %d; ",
conts->lin_idx);
pgf_print_fid(ccat->fid, out, err);
gu_puts("] ", out, err);
pgf_print_fid(ccat->fid, out, err);
gu_printf(out, err, ".chunk_count=%d\n", ccat->chunk_count);
}
pgf_print_production(ccat->fid, prod, out, err);
gu_pool_free(tmp_pool);
#endif
}
}
if (len <= max)
if (pgf_parsing_scan_helper(ps, state, k+1, j, len, max))
found = true;
break;
}
}
return found;
}
static void
pgf_parsing_scan(PgfParsing *ps)
{
size_t len = strlen(ps->sentence);
PgfParseState* state =
pgf_new_parse_state(ps, 0, BIND_SOFT);
while (state != NULL && state->end_offset < len) {
if (state->needs_bind) {
// We have encountered two tokens without space in between.
// Those can be accepted only if there is a BIND token
// in between. We encode this by having one more state
// at the same offset. A transition between these two
// states is possible only with the BIND token.
state =
pgf_new_parse_state(ps, state->end_offset, BIND_HARD);
}
if (!pgf_parsing_scan_helper
(ps, state,
0, gu_seq_length(ps->concr->sequences)-1,
1, len-state->end_offset)) {
// skip one character and try again
GuString s = ps->sentence+state->end_offset;
gu_utf8_decode((const uint8_t**) &s);
pgf_new_parse_state(ps, s-ps->sentence, BIND_NONE);
}
if (state == ps->before)
state = ps->after;
else
state = state->next;
}
}
static void
pgf_parsing_add_transition(PgfParsing* ps, PgfToken tok, PgfItem* item)
{
@@ -1138,14 +1058,36 @@ pgf_parsing_add_transition(PgfParsing* ps, PgfToken tok, PgfItem* item)
if (!ps->before->needs_bind && cmp_string(&current, tok, ps->case_sensitive) == 0) {
PgfParseState* state =
pgf_new_parse_state(ps, (current.ptr - ps->sentence),
BIND_NONE);
pgf_parsing_push_item(state, item);
BIND_NONE,
item->inside_prob+item->conts->outside_prob);
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
} else {
pgf_item_free(ps, item);
}
}
}
static void
pgf_parsing_predict_lexeme(PgfParsing* ps, PgfItemConts* conts,
PgfProductionIdxEntry* entry,
size_t offset, size_t sym_idx)
{
GuVariantInfo i = { PGF_PRODUCTION_APPLY, entry->papp };
PgfProduction prod = gu_variant_close(i);
PgfItem* item =
pgf_new_item(ps, conts, prod);
PgfSymbols* syms = entry->papp->fun->lins[conts->lin_idx]->syms;
item->sym_idx = sym_idx;
pgf_item_set_curr_symbol(item, ps->pool);
prob_t prob = item->inside_prob+item->conts->outside_prob;
PgfParseState* state =
pgf_new_parse_state(ps, offset, BIND_NONE, prob);
if (state->viterbi_prob > prob) {
state->viterbi_prob = prob;
}
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
}
static void
pgf_parsing_td_predict(PgfParsing* ps,
PgfItem* item, PgfCCat* ccat, size_t lin_idx)
@@ -1193,36 +1135,34 @@ pgf_parsing_td_predict(PgfParsing* ps,
pgf_parsing_push_production(ps, ps->before, conts, prod);
}
// Top-down prediction for epsilon lexical rules if any
PgfSequence* seq = gu_seq_index(ps->concr->sequences, PgfSequence, 0);
if (gu_seq_length(seq->syms) == 0 && seq->idx != NULL) {
// Bottom-up prediction for lexical and epsilon rules
size_t n_idcs = gu_buf_length(ps->before->lexicon_idx);
for (size_t i = 0; i < n_idcs; i++) {
PgfLexiconIdxEntry* lentry =
gu_buf_index(ps->before->lexicon_idx, PgfLexiconIdxEntry, i);
PgfProductionIdxEntry key;
key.ccat = ccat;
key.lin_idx = lin_idx;
key.papp = NULL;
PgfProductionIdxEntry* value =
gu_seq_binsearch(gu_buf_data_seq(seq->idx),
gu_seq_binsearch(gu_buf_data_seq(lentry->idx),
pgf_production_idx_entry_order,
PgfProductionIdxEntry, &key);
if (value != NULL) {
GuVariantInfo i = { PGF_PRODUCTION_APPLY, value->papp };
PgfProduction prod = gu_variant_close(i);
pgf_parsing_push_production(ps, ps->before, conts, prod);
pgf_parsing_predict_lexeme(ps, conts, value, lentry->offset, lentry->sym_idx);
PgfProductionIdxEntry* start =
gu_buf_data(seq->idx);
gu_buf_data(lentry->idx);
PgfProductionIdxEntry* end =
start + gu_buf_length(seq->idx)-1;
start + gu_buf_length(lentry->idx)-1;
PgfProductionIdxEntry* left = value-1;
while (left >= start &&
value->ccat->fid == left->ccat->fid &&
value->lin_idx == left->lin_idx) {
GuVariantInfo i = { PGF_PRODUCTION_APPLY, left->papp };
PgfProduction prod = gu_variant_close(i);
pgf_parsing_push_production(ps, ps->before, conts, prod);
pgf_parsing_predict_lexeme(ps, conts, left, lentry->offset, lentry->sym_idx);
left--;
}
@@ -1230,9 +1170,7 @@ pgf_parsing_td_predict(PgfParsing* ps,
while (right <= end &&
value->ccat->fid == right->ccat->fid &&
value->lin_idx == right->lin_idx) {
GuVariantInfo i = { PGF_PRODUCTION_APPLY, right->papp };
PgfProduction prod = gu_variant_close(i);
pgf_parsing_push_production(ps, ps->before, conts, prod);
pgf_parsing_predict_lexeme(ps, conts, right, lentry->offset, lentry->sym_idx);
right++;
}
}
@@ -1271,7 +1209,7 @@ pgf_parsing_pre(PgfParsing* ps, PgfItem* item, PgfSymbols* syms)
} else {
item->alt = 0;
pgf_item_advance(item, ps->pool);
pgf_parsing_push_item(ps->before, item);
gu_buf_heap_push(ps->before->agenda, pgf_item_prob_order, &item);
}
}
@@ -1401,8 +1339,9 @@ pgf_parsing_symbol(PgfParsing* ps, PgfItem* item, PgfSymbol sym)
item->curr_sym = gu_null_variant;
item->sym_idx = gu_seq_length(syms);
PgfParseState* state =
pgf_new_parse_state(ps, offset, BIND_NONE);
pgf_parsing_push_item(state, item);
pgf_new_parse_state(ps, offset, BIND_NONE,
item->inside_prob+item->conts->outside_prob);
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
match = true;
}
}
@@ -1445,10 +1384,11 @@ pgf_parsing_symbol(PgfParsing* ps, PgfItem* item, PgfSymbol sym)
if (ps->before->start_offset == ps->before->end_offset &&
ps->before->needs_bind) {
PgfParseState* state =
pgf_new_parse_state(ps, ps->before->end_offset, BIND_HARD);
pgf_new_parse_state(ps, ps->before->end_offset, BIND_HARD,
item->inside_prob+item->conts->outside_prob);
if (state != NULL) {
pgf_item_advance(item, ps->pool);
pgf_parsing_push_item(state, item);
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
} else {
pgf_item_free(ps, item);
}
@@ -1462,10 +1402,11 @@ pgf_parsing_symbol(PgfParsing* ps, PgfItem* item, PgfSymbol sym)
if (ps->before->start_offset == ps->before->end_offset) {
if (ps->before->needs_bind) {
PgfParseState* state =
pgf_new_parse_state(ps, ps->before->end_offset, BIND_HARD);
pgf_new_parse_state(ps, ps->before->end_offset, BIND_HARD,
item->inside_prob+item->conts->outside_prob);
if (state != NULL) {
pgf_item_advance(item, ps->pool);
pgf_parsing_push_item(state, item);
gu_buf_heap_push(state->agenda, pgf_item_prob_order, &item);
} else {
pgf_item_free(ps, item);
}
@@ -1474,7 +1415,7 @@ pgf_parsing_symbol(PgfParsing* ps, PgfItem* item, PgfSymbol sym)
}
} else {
pgf_item_advance(item, ps->pool);
pgf_parsing_push_item(ps->before, item);
gu_buf_heap_push(ps->before->agenda, pgf_item_prob_order, &item);
}
break;
}
@@ -1725,7 +1666,8 @@ pgf_parsing_init(PgfConcr* concr, PgfCId cat,
ps->heuristic_factor = heuristic_factor;
}
pgf_parsing_scan(ps);
PgfParseState* state =
pgf_new_parse_state(ps, 0, BIND_SOFT, 0);
int fidString = -1;
PgfCCat* start_ccat = gu_new(PgfCCat, ps->pool);
@@ -1745,7 +1687,7 @@ pgf_parsing_init(PgfConcr* concr, PgfCId cat,
#endif
PgfItemConts* conts =
pgf_parsing_get_conts(ps->before, start_ccat, 0, ps->pool);
pgf_parsing_get_conts(state, start_ccat, 0, ps->pool);
gu_buf_push(conts->items, PgfItem*, NULL);
size_t n_ccats = gu_seq_length(cnccat->cats);