spaCy/spacy/syntax/_beam_utils.pyx

# cython: infer_types=True, profile=True
cimport numpy as np
from cpython.ref cimport PyObject, Py_XDECREF
from thinc.extra.search cimport Beam
from thinc.extra.search cimport MaxViolation

from thinc.extra.search import MaxViolation
import numpy

from ..typedefs cimport hash_t, class_t
from .transition_system cimport TransitionSystem, Transition
from ..gold cimport GoldParse
from .stateclass cimport StateC, StateClass

from ..errors import Errors


# These are passed as callbacks to thinc.search.Beam
cdef int transition_state(void* _dest, void* _src, class_t clas, void* _moves) except -1:
    dest = <StateC*>_dest
    src = <StateC*>_src
    moves = <const Transition*>_moves
    dest.clone(src)
    moves[clas].do(dest, moves[clas].label)
    dest.push_hist(clas)


cdef int check_final_state(void* _state, void* extra_args) except -1:
    state = <StateC*>_state
    return state.is_final()


cdef hash_t hash_state(void* _state, void* _) except 0:
    state = <StateC*>_state
    if state.is_final():
        return 1
    else:
        return state.hash()


def collect_states(beams):
    cdef StateClass state
    cdef Beam beam
    states = []
    for state_or_beam in beams:
        if isinstance(state_or_beam, StateClass):
            states.append(state_or_beam)
        else:
            beam = state_or_beam
            state = StateClass.borrow(<StateC*>beam.at(0))
            states.append(state)
    return states


cdef class ParserBeam(object):
    cdef public TransitionSystem moves
    cdef public object states
    cdef public object golds
    cdef public object beams
    cdef public object dones

    def __init__(self, TransitionSystem moves, states, golds,
                 int width, float density=0.):
        self.moves = moves
        self.states = states
        self.golds = golds
        self.beams = []
        cdef Beam beam
        cdef StateClass state
        cdef StateC* st
        for state in states:
            beam = Beam(self.moves.n_moves, width, min_density=density)
            beam.initialize(self.moves.init_beam_state,
                            self.moves.del_beam_state, state.c.length,
                            state.c._sent)
            for i in range(beam.width):
                st = <StateC*>beam.at(i)
                st.offset = state.c.offset
            self.beams.append(beam)
        self.dones = [False] * len(self.beams)

    @property
    def is_done(self):
        return all(b.is_done or self.dones[i]
                   for i, b in enumerate(self.beams))

    def __getitem__(self, i):
        return self.beams[i]

    def __len__(self):
        return len(self.beams)

    def advance(self, scores, follow_gold=False):
        cdef Beam beam
        for i, beam in enumerate(self.beams):
            if beam.is_done or not scores[i].size or self.dones[i]:
                continue
            self._set_scores(beam, scores[i])
            if self.golds is not None:
                self._set_costs(beam, self.golds[i], follow_gold=follow_gold)
            beam.advance(transition_state, hash_state, <void*>self.moves.c)
            beam.check_done(check_final_state, NULL)
            # This handles the non-monotonic stuff for the parser.
            if beam.is_done and self.golds is not None:
                for j in range(beam.size):
                    state = StateClass.borrow(<StateC*>beam.at(j))
                    if state.is_final():
                        try:
                            if self.moves.is_gold_parse(state, self.golds[i]):
                                beam._states[j].loss = 0.0
                        except NotImplementedError:
                            break

    def _set_scores(self, Beam beam, float[:, ::1] scores):
        cdef float* c_scores = &scores[0, 0]
        cdef int nr_state = min(scores.shape[0], beam.size)
        cdef int nr_class = scores.shape[1]
        for i in range(nr_state):
            state = <StateC*>beam.at(i)
            if not state.is_final():
                for j in range(nr_class):
                    beam.scores[i][j] = c_scores[i * nr_class + j]
                self.moves.set_valid(beam.is_valid[i], state)
            else:
                for j in range(beam.nr_class):
                    beam.scores[i][j] = 0
                    beam.costs[i][j] = 0

    def _set_costs(self, Beam beam, GoldParse gold, int follow_gold=False):
        for i in range(beam.size):
            state = StateClass.borrow(<StateC*>beam.at(i))
            if not state.is_final():
                self.moves.set_costs(beam.is_valid[i], beam.costs[i],
                                     state, gold)
                if follow_gold:
                    min_cost = 0
                    for j in range(beam.nr_class):
                        if beam.is_valid[i][j] and beam.costs[i][j] < min_cost:
                            min_cost = beam.costs[i][j]
                    for j in range(beam.nr_class):
                        if beam.costs[i][j] > min_cost:
                            beam.is_valid[i][j] = 0


def get_token_ids(states, int n_tokens):
    cdef StateClass state
    cdef np.ndarray ids = numpy.zeros((len(states), n_tokens),
                                      dtype='int32', order='C')
    c_ids = <int*>ids.data
    for i, state in enumerate(states):
        if not state.is_final():
            state.c.set_context_tokens(c_ids, n_tokens)
        else:
            ids[i] = -1
        c_ids += ids.shape[1]
    return ids


nr_update = 0


def update_beam(TransitionSystem moves, int nr_feature, int max_steps,
                states, golds,
                state2vec, vec2scores,
                int width, losses=None, drop=0.,
                early_update=True, beam_density=0.0):
    global nr_update
    cdef MaxViolation violn
    nr_update += 1
    pbeam = ParserBeam(moves, states, golds, width=width, density=beam_density)
    gbeam = ParserBeam(moves, states, golds, width=width, density=beam_density)
    cdef StateClass state
    beam_maps = []
    backprops = []
    violns = [MaxViolation() for _ in range(len(states))]
    for t in range(max_steps):
        if pbeam.is_done and gbeam.is_done:
            break
        # The beam maps let us find the right row in the flattened scores
        # arrays for each state. States are identified by (example id,
        # history). We keep a different beam map for each step (since we'll
        # have a flat scores array for each step). The beam map will let us
        # take the per-state losses, and compute the gradient for each (step,
        # state, class).
        beam_maps.append({})
        # Gather all states from the two beams in a list. Some stats may occur
        # in both beams. To figure out which beam each state belonged to,
        # we keep two lists of indices, p_indices and g_indices
        states, p_indices, g_indices = get_states(pbeam, gbeam, beam_maps[-1],
                                                  nr_update)
        if not states:
            break
        # Now that we have our flat list of states, feed them through the model
        token_ids = get_token_ids(states, nr_feature)
        vectors, bp_vectors = state2vec.begin_update(token_ids, drop=drop)
        scores, bp_scores = vec2scores.begin_update(vectors, drop=drop)

        # Store the callbacks for the backward pass
        backprops.append((token_ids, bp_vectors, bp_scores))

        # Unpack the flat scores into lists for the two beams. The indices arrays
        # tell us which example and state the scores-row refers to.
        p_scores = [numpy.ascontiguousarray(scores[indices], dtype='f')
                    for indices in p_indices]
        g_scores = [numpy.ascontiguousarray(scores[indices], dtype='f')
                    for indices in g_indices]
        # Now advance the states in the beams. The gold beam is constrained to
        # to follow only gold analyses.
        pbeam.advance(p_scores)
        gbeam.advance(g_scores, follow_gold=True)
        # Track the "maximum violation", to use in the update.
        for i, violn in enumerate(violns):
            violn.check_crf(pbeam[i], gbeam[i])
    histories = []
    losses = []
    for violn in violns:
        if violn.p_hist:
            histories.append(violn.p_hist + violn.g_hist)
            losses.append(violn.p_probs + violn.g_probs)
        else:
            histories.append([])
            losses.append([])
    states_d_scores = get_gradient(moves.n_moves, beam_maps, histories, losses)
    beams = list(pbeam.beams) + list(gbeam.beams)
    return states_d_scores, backprops[:len(states_d_scores)], beams


def get_states(pbeams, gbeams, beam_map, nr_update):
    seen = {}
    states = []
    p_indices = []
    g_indices = []
    cdef Beam pbeam, gbeam
    if len(pbeams) != len(gbeams):
        raise ValueError(Errors.E079.format(pbeams=len(pbeams), gbeams=len(gbeams)))
    for eg_id, (pbeam, gbeam) in enumerate(zip(pbeams, gbeams)):
        p_indices.append([])
        g_indices.append([])
        for i in range(pbeam.size):
            state = StateClass.borrow(<StateC*>pbeam.at(i))
            if not state.is_final():
                key = tuple([eg_id] + pbeam.histories[i])
                if key in seen:
                    raise ValueError(Errors.E080.format(key=key))
                seen[key] = len(states)
                p_indices[-1].append(len(states))
                states.append(state)
        beam_map.update(seen)
        for i in range(gbeam.size):
            state = StateClass.borrow(<StateC*>gbeam.at(i))
            if not state.is_final():
                key = tuple([eg_id] + gbeam.histories[i])
                if key in seen:
                    g_indices[-1].append(seen[key])
                else:
                    g_indices[-1].append(len(states))
                    beam_map[key] = len(states)
                    states.append(state)
    p_idx = [numpy.asarray(idx, dtype='i') for idx in p_indices]
    g_idx = [numpy.asarray(idx, dtype='i') for idx in g_indices]
    return states, p_idx, g_idx


def get_gradient(nr_class, beam_maps, histories, losses):
    """The global model assigns a loss to each parse. The beam scores
    are additive, so the same gradient is applied to each action
    in the history. This gives the gradient of a single *action*
    for a beam state -- so we have "the gradient of loss for taking
    action i given history H."

    Histories: Each hitory is a list of actions
    Each candidate has a history
    Each beam has multiple candidates
    Each batch has multiple beams
    So history is list of lists of lists of ints
    """
    grads = []
    nr_steps = []
    for eg_id, hists in enumerate(histories):
        nr_step = 0
        for loss, hist in zip(losses[eg_id], hists):
            if loss != 0.0 and not numpy.isnan(loss):
                nr_step = max(nr_step, len(hist))
        nr_steps.append(nr_step)
    for i in range(max(nr_steps)):
        grads.append(numpy.zeros((max(beam_maps[i].values())+1, nr_class),
                                 dtype='f'))
    if len(histories) != len(losses):
        raise ValueError(Errors.E081.format(n_hist=len(histories), losses=len(losses)))
    for eg_id, hists in enumerate(histories):
        for loss, hist in zip(losses[eg_id], hists):
            if loss == 0.0 or numpy.isnan(loss):
                continue
            key = tuple([eg_id])
            # Adjust loss for length
            # We need to do this because each state in a short path is scored
            # multiple times, as we add in the average cost when we run out
            # of actions.
            avg_loss = loss / len(hist)
            loss += avg_loss * (nr_steps[eg_id] - len(hist))
            for j, clas in enumerate(hist):
                i = beam_maps[j][key]
                # In step j, at state i action clas
                # resulted in loss
                grads[j][i, clas] += loss
                key = key + tuple([clas])
    return grads


def cleanup_beam(Beam beam):
    cdef StateC* state
    # Once parsing has finished, states in beam may not be unique. Is this
    # correct?
    seen = set()
    for i in range(beam.width):
        addr = <size_t>beam._parents[i].content
        if addr not in seen:
            state = <StateC*>addr
            del state
            seen.add(addr)
        else:
            raise ValueError(Errors.E023.format(addr=addr, i=i))
        addr = <size_t>beam._states[i].content
        if addr not in seen:
            state = <StateC*>addr
            del state
            seen.add(addr)
        else:
            raise ValueError(Errors.E023.format(addr=addr, i=i))