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"""Representing suggested subjects.""" |
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import collections |
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import itertools |
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import numpy as np |
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from scipy.sparse import csr_array, dok_array |
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SubjectSuggestion = collections.namedtuple("SubjectSuggestion", "subject_id score") |
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def vector_to_suggestions(vector, limit): |
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limit = min(len(vector), limit) |
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topk_idx = np.argpartition(vector, -limit)[-limit:] |
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return ( |
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SubjectSuggestion(subject_id=idx, score=float(vector[idx])) for idx in topk_idx |
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) |
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def filter_suggestion(preds, limit=None, threshold=0.0): |
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"""filter a 2D sparse suggestion array (csr_array), retaining only the |
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top K suggestions with a score above or equal to the threshold for each |
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individual prediction; the rest will be left as zeros""" |
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filtered = dok_array(preds.shape, dtype=np.float32) |
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for row in range(preds.shape[0]): |
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arow = preds.getrow(row) |
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top_k = arow.data.argsort()[::-1] |
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if limit is not None: |
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top_k = top_k[:limit] |
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for idx in top_k: |
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val = arow.data[idx] |
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if val < threshold: |
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break |
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filtered[row, arow.indices[idx]] = val |
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return filtered.tocsr() |
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class SuggestionResult: |
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"""Suggestions for a single document, backed by a row of a sparse array.""" |
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def __init__(self, array, idx): |
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self._array = array |
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self._idx = idx |
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def __iter__(self): |
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_, cols = self._array[[self._idx], :].nonzero() |
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suggestions = [ |
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SubjectSuggestion(subject_id=col, score=float(self._array[self._idx, col])) |
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for col in cols |
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] |
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return iter( |
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sorted(suggestions, key=lambda suggestion: suggestion.score, reverse=True) |
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) |
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def as_vector(self): |
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return self._array[[self._idx], :].toarray()[0] |
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def __len__(self): |
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_, cols = self._array[[self._idx], :].nonzero() |
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return len(cols) |
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class SuggestionBatch: |
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"""Subject suggestions for a batch of documents.""" |
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def __init__(self, array): |
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"""Create a new SuggestionBatch from a csr_array""" |
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assert isinstance(array, csr_array) |
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self.array = array |
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@classmethod |
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def from_sequence(cls, suggestion_results, subject_index, limit=None): |
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"""Create a new SuggestionBatch from a sequence where each item is |
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a sequence of SubjectSuggestion objects.""" |
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deprecated = set(subject_index.deprecated_ids()) |
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ar = dok_array((len(suggestion_results), len(subject_index)), dtype=np.float32) |
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for idx, result in enumerate(suggestion_results): |
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for suggestion in itertools.islice(result, limit): |
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if suggestion.subject_id in deprecated or suggestion.score <= 0.0: |
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continue |
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ar[idx, suggestion.subject_id] = min(suggestion.score, 1.0) |
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return cls(ar.tocsr()) |
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@classmethod |
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def from_averaged(cls, batches, weights): |
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"""Create a new SuggestionBatch where the subject scores are the |
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weighted average of scores in several SuggestionBatches""" |
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avg_array = sum( |
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[batch.array * weight for batch, weight in zip(batches, weights)] |
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) / sum(weights) |
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return SuggestionBatch(avg_array) |
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def filter(self, limit=None, threshold=0.0): |
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"""Return a subset of the hits, filtered by the given limit and |
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score threshold, as another SuggestionBatch object.""" |
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return SuggestionBatch(filter_suggestion(self.array, limit, threshold)) |
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def __getitem__(self, idx): |
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if idx < 0 or idx >= len(self): |
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raise IndexError |
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return SuggestionResult(self.array, idx) |
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def __len__(self): |
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return self.array.shape[0] |
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class SuggestionResults: |
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"""Subject suggestions for a potentially very large number of documents.""" |
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def __init__(self, batches): |
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"""Initialize a new SuggestionResults from an iterable that provides |
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SuggestionBatch objects.""" |
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self.batches = batches |
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def filter(self, limit=None, threshold=0.0): |
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"""Return a view of these suggestions, filtered by the given limit |
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and/or threshold, as another SuggestionResults object.""" |
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return SuggestionResults( |
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(batch.filter(limit, threshold) for batch in self.batches) |
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) |
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129
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def __iter__(self): |
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return iter(itertools.chain.from_iterable(self.batches)) |
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NatLibFi /
Annif
