spaCy/spacy/syntax/arc_eager.pyx

from __future__ import unicode_literals

from ._state cimport State
from ._state cimport has_head, get_idx, get_s0, get_n0, get_left, get_right
from ._state cimport is_final, at_eol, pop_stack, push_stack, add_dep
from ._state cimport head_in_buffer, children_in_buffer
from ._state cimport head_in_stack, children_in_stack
from ._state cimport count_left_kids

from ..structs cimport TokenC

from .transition_system cimport do_func_t, get_cost_func_t
from .conll cimport GoldParse


DEF NON_MONOTONIC = True
DEF USE_BREAK = True

cdef weight_t MIN_SCORE = -90000

# Break transition from here
# http://www.aclweb.org/anthology/P13-1074
cdef enum:
    SHIFT
    REDUCE
    LEFT
    RIGHT

    BREAK

    CONSTITUENT
    ADJUST

    N_MOVES


MOVE_NAMES = [None] * N_MOVES
MOVE_NAMES[SHIFT] = 'S'
MOVE_NAMES[REDUCE] = 'D'
MOVE_NAMES[LEFT] = 'L'
MOVE_NAMES[RIGHT] = 'R'
MOVE_NAMES[BREAK] = 'B'
MOVE_NAMES[CONSTITUENT] = 'C'
MOVE_NAMES[ADJUST] = 'A'


cdef do_func_t[N_MOVES] do_funcs
cdef get_cost_func_t[N_MOVES] get_cost_funcs


cdef class ArcEager(TransitionSystem):
    @classmethod
    def get_labels(cls, gold_parses):
        move_labels = {SHIFT: {'': True}, REDUCE: {'': True}, RIGHT: {},
                       LEFT: {'ROOT': True}, BREAK: {'ROOT': True},
                       CONSTITUENT: {}, ADJUST: {'': True}}
        for raw_text, segmented, (ids, words, tags, heads, labels, iob), ctnts in gold_parses:
            for child, head, label in zip(ids, heads, labels):
                if label != 'ROOT':
                    if head < child:
                        move_labels[RIGHT][label] = True
                    elif head > child:
                        move_labels[LEFT][label] = True
            for start, end, label in ctnts:
                move_labels[CONSTITUENT][label] = True
        return move_labels

    cdef int preprocess_gold(self, GoldParse gold) except -1:
        for i in range(gold.length):
            gold.c_heads[i] = gold.heads[i]
            gold.c_labels[i] = self.strings[gold.labels[i]]
        for end, brackets in gold.brackets.items():
            for start, label_strs in brackets.items():
                gold.c_brackets[start][end] = 1
                for label_str in label_strs:
                    # Add the encoded label to the set
                    gold.brackets[end][start].add(self.strings[label_str])

    cdef Transition lookup_transition(self, object name) except *:
        if '-' in name:
            move_str, label_str = name.split('-', 1)
            label = self.label_ids[label_str]
        else:
            label = 0
        move = MOVE_NAMES.index(move_str)
        for i in range(self.n_moves):
            if self.c[i].move == move and self.c[i].label == label:
                return self.c[i]

    def move_name(self, int move, int label):
        label_str = self.strings[label]
        if label_str:
            return MOVE_NAMES[move] + '-' + label_str
        else:
            return MOVE_NAMES[move]

    cdef Transition init_transition(self, int clas, int move, int label) except *:
        # TODO: Apparent Cython bug here when we try to use the Transition()
        # constructor with the function pointers
        cdef Transition t
        t.score = 0
        t.clas = clas
        t.move = move
        t.label = label
        t.do = do_funcs[move]
        t.get_cost = get_cost_funcs[move]
        return t

    cdef int initialize_state(self, State* state) except -1:
        push_stack(state)

    cdef int finalize_state(self, State* state) except -1:
        cdef int root_label = self.strings['ROOT']
        for i in range(state.sent_len):
            if state.sent[i].head == 0 and state.sent[i].dep == 0:
                state.sent[i].dep = root_label

    cdef Transition best_valid(self, const weight_t* scores, const State* s) except *:
        cdef bint[N_MOVES] is_valid
        is_valid[SHIFT] = _can_shift(s)
        is_valid[REDUCE] = _can_reduce(s)
        is_valid[LEFT] = _can_left(s)
        is_valid[RIGHT] = _can_right(s)
        is_valid[BREAK] = _can_break(s)
        is_valid[CONSTITUENT] = _can_constituent(s)
        is_valid[ADJUST] = _can_adjust(s)
        cdef Transition best
        cdef weight_t score = MIN_SCORE
        cdef int i
        for i in range(self.n_moves):
            if scores[i] > score and is_valid[self.c[i].move]:
                best = self.c[i]
                score = scores[i]
        assert best.clas < self.n_moves
        assert score > MIN_SCORE
        # Label Shift moves with the best Right-Arc label, for non-monotonic
        # actions
        if best.move == SHIFT:
            score = MIN_SCORE
            for i in range(self.n_moves):
                if self.c[i].move == RIGHT and scores[i] > score:
                    best.label = self.c[i].label
                    score = scores[i]
        return best


cdef int _do_shift(const Transition* self, State* state) except -1:
    # Set the dep label, in case we need it after we reduce
    if NON_MONOTONIC:
        state.sent[state.i].dep = self.label
    push_stack(state)


cdef int _do_left(const Transition* self, State* state) except -1:
    # Interpret left-arcs from EOL as attachment to root
    if at_eol(state):
        add_dep(state, state.stack[0], state.stack[0], self.label)
    else:
        add_dep(state, state.i, state.stack[0], self.label)
    pop_stack(state)


cdef int _do_right(const Transition* self, State* state) except -1:
    add_dep(state, state.stack[0], state.i, self.label)
    push_stack(state)


cdef int _do_reduce(const Transition* self, State* state) except -1:
    if NON_MONOTONIC and not has_head(get_s0(state)):
        add_dep(state, state.stack[-1], state.stack[0], get_s0(state).dep)
    pop_stack(state)


cdef int _do_break(const Transition* self, State* state) except -1:
    state.sent[state.i-1].sent_end = True
    while state.stack_len != 0:
        if get_s0(state).head == 0:
            get_s0(state).dep = self.label
        state.stack -= 1
        state.stack_len -= 1
    if not at_eol(state):
        push_stack(state)


cdef int _do_constituent(const Transition* self, State* state) except -1:
    cdef const TokenC* s0 = get_s0(state)
    if state.ctnt.head == get_idx(state, s0):
        start = state.ctnt.start
    else:
        start = get_idx(state, s0)
    state.ctnt += 1
    state.ctnt.start = start
    state.ctnt.end = s0.r_edge
    state.ctnt.head = get_idx(state, s0)
    state.ctnt.label = self.label


cdef int _do_adjust(const Transition* self, State* state) except -1:
    cdef const TokenC* child
    cdef const TokenC* s0 = get_s0(state)
    cdef int n_left = count_left_kids(s0)
    for i in range(1, n_left):
        child = get_left(state, s0, i)
        assert child is not NULL
        if child.l_edge < state.ctnt.start:
            state.ctnt.start = child.l_edge
            break
    else:
        msg = ("Error moving bracket --- Move should be invalid if "
               "no left edge to move to.")
        raise Exception(msg)


do_funcs[SHIFT] = _do_shift
do_funcs[REDUCE] = _do_reduce
do_funcs[LEFT] = _do_left
do_funcs[RIGHT] = _do_right
do_funcs[BREAK] = _do_break
do_funcs[CONSTITUENT] = _do_constituent
do_funcs[ADJUST] = _do_adjust


cdef int _shift_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_shift(s):
        return 9000
    cost = 0
    cost += head_in_stack(s, s.i, gold.c_heads)
    cost += children_in_stack(s, s.i, gold.c_heads)
    if NON_MONOTONIC:
        cost += gold.c_heads[s.stack[0]] == s.i
    # If we can break, and there's no cost to doing so, we should
    if _can_break(s) and _break_cost(self, s, gold) == 0:
        cost += 1
    return cost


cdef int _right_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_right(s):
        return 9000
    cost = 0
    if gold.c_heads[s.i] == s.stack[0]:
        cost += self.label != gold.c_labels[s.i]
        return cost
    cost += head_in_buffer(s, s.i, gold.c_heads)
    cost += children_in_stack(s, s.i, gold.c_heads)
    cost += head_in_stack(s, s.i, gold.c_heads)
    if NON_MONOTONIC:
        cost += gold.c_heads[s.stack[0]] == s.i
    return cost


cdef int _left_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_left(s):
        return 9000
    cost = 0
    if gold.c_heads[s.stack[0]] == s.i:
        cost += self.label != gold.c_labels[s.stack[0]]
        return cost
    # If we're at EOL, then the left arc will add an arc to ROOT.
    elif at_eol(s):
        # Are we root?
        cost += gold.c_heads[s.stack[0]] != s.stack[0]
        # Are we labelling correctly?
        cost += self.label != gold.c_labels[s.stack[0]]
        return cost

    cost += head_in_buffer(s, s.stack[0], gold.c_heads)
    cost += children_in_buffer(s, s.stack[0], gold.c_heads)
    if NON_MONOTONIC and s.stack_len >= 2:
        cost += gold.c_heads[s.stack[0]] == s.stack[-1]
    cost += gold.c_heads[s.stack[0]] == s.stack[0]
    return cost


cdef int _reduce_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_reduce(s):
        return 9000
    cdef int cost = 0
    cost += children_in_buffer(s, s.stack[0], gold.c_heads)
    if NON_MONOTONIC:
        cost += head_in_buffer(s, s.stack[0], gold.c_heads)
    return cost


cdef int _break_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_break(s):
        return 9000
    # When we break, we Reduce all of the words on the stack.
    cdef int cost = 0
    # Number of deps between S0...Sn and N0...Nn
    for i in range(s.i, s.sent_len):
        cost += children_in_stack(s, i, gold.c_heads)
        cost += head_in_stack(s, i, gold.c_heads)
    return cost


cdef int _constituent_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_constituent(s):
        return 9000
    # The gold standard is indexed by end, then by start, then a set of labels
    brackets = gold.brackets(get_s0(s).r_edge, {})
    if not brackets:
        return 2 # 2 loss for bad bracket, only 1 for good bracket bad label
    # Index the current brackets in the state
    existing = set()
    for i in range(s.ctnt_len):
        if ctnt.end == s.r_edge and ctnt.label == self.label:
            existing.add(ctnt.start)
    cdef int loss = 2
    cdef const TokenC* child
    cdef const TokenC* s0 = get_s0(s)
    cdef int n_left = count_left_kids(s0)
    # Iterate over the possible start positions, and check whether we have a
    # (start, end, label) match to the gold tree
    for i in range(1, n_left):
        child = get_left(s, s0, i)
        if child.l_edge in brackets and child.l_edge not in existing:
            if self.label in brackets[child.l_edge]
                return 0
            else:
                loss = 1 # If we see the start position, set loss to 1
    return loss
 

cdef int _adjust_cost(const Transition* self, const State* s, GoldParse gold) except -1:
    if not _can_adjust(s):
        return 9000
    # The gold standard is indexed by end, then by start, then a set of labels
    gold_starts = gold.brackets(get_s0(s).r_edge, {})
    # Case 1: There are 0 brackets ending at this word.
    # --> Cost is sunk, but must allow brackets to begin
    if not gold_starts:
        return 0
    # Is the top bracket correct?
    gold_labels = gold_starts.get(s.ctnt.start, set())
    # TODO: Case where we have a unary rule
    # TODO: Case where two brackets end on this word, with top bracket starting
    # before

    cdef const TokenC* child
    cdef const TokenC* s0 = get_s0(s)
    cdef int n_left = count_left_kids(s0)
    cdef int i
    # Iterate over the possible start positions, and check whether we have a
    # (start, end, label) match to the gold tree
    for i in range(1, n_left):
        child = get_left(s, s0, i)
        if child.l_edge in brackets:
            if self.label in brackets[child.l_edge]:
                return 0
            else:
                loss = 1 # If we see the start position, set loss to 1
    return loss


get_cost_funcs[SHIFT] = _shift_cost
get_cost_funcs[REDUCE] = _reduce_cost
get_cost_funcs[LEFT] = _left_cost
get_cost_funcs[RIGHT] = _right_cost
get_cost_funcs[BREAK] = _break_cost
get_cost_funcs[CONSTITUENT] = _constituent_cost
get_cost_funcs[ADJUST] = _adjust_cost


cdef inline bint _can_shift(const State* s) nogil:
    return not at_eol(s)


cdef inline bint _can_right(const State* s) nogil:
    return s.stack_len >= 1 and not at_eol(s)


cdef inline bint _can_left(const State* s) nogil:
    if NON_MONOTONIC:
        return s.stack_len >= 1
    else:
        return s.stack_len >= 1 and not has_head(get_s0(s))


cdef inline bint _can_reduce(const State* s) nogil:
    if NON_MONOTONIC:
        return s.stack_len >= 2
    else:
        return s.stack_len >= 2 and has_head(get_s0(s))


cdef inline bint _can_break(const State* s) nogil:
    cdef int i
    if not USE_BREAK:
        return False
    elif at_eol(s):
        return False
    else:
        # If stack is disconnected, cannot break
        seen_headless = False
        for i in range(s.stack_len):
            if s.sent[s.stack[-i]].head == 0:
                if seen_headless:
                    return False
                else:
                    seen_headless = True
        return True


cdef inline bint _can_constituent(const State* s) nogil:
    return s.stack_len >= 1


cdef inline bint _can_adjust(const State* s) nogil:
    # Need a left child to move the bracket to
    cdef const TokenC* child
    cdef const TokenC* s0 = get_s0(s)
    cdef int n_left = count_left_kids(s0)
    cdef int i
    for i in range(1, n_left):
        child = get_left(s, s0, i)
        if child.l_edge < s.ctnt.start:
            return True
    else:
        return False