From abbe3e44b0dd860c23a2d691a0658b2a751bc944 Mon Sep 17 00:00:00 2001
From: Matthew Honnibal <honnibal@gmail.com>
Date: Wed, 5 Nov 2014 00:37:59 +1100
Subject: [PATCH] * Move spacy.pos tagger to spacy.tagger, and generalize it so
 that it can take on other tagging tasks, given a different set of feature
 templates.

---
 spacy/tagger.pxd | 32 +++++++++++++++++
 spacy/tagger.pyx | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 123 insertions(+)
 create mode 100644 spacy/tagger.pxd
 create mode 100644 spacy/tagger.pyx

diff --git a/spacy/tagger.pxd b/spacy/tagger.pxd
new file mode 100644
index 000000000..514e9693e
--- /dev/null
+++ b/spacy/tagger.pxd
@@ -0,0 +1,32 @@
+from cymem.cymem cimport Pool
+
+from thinc.learner cimport LinearModel
+from thinc.features cimport Extractor
+from thinc.typedefs cimport atom_t, feat_t, weight_t, class_t
+
+from .tokens cimport Tokens
+
+
+cdef enum TagType:
+    POS
+    ENTITY
+    SENSE
+
+
+cdef class Tagger:
+    cpdef int set_tags(self, Tokens tokens) except -1
+    cpdef class_t predict(self, int i, Tokens tokens) except 0
+    cpdef int tell_answer(self, class_t gold) except -1
+ 
+    cpdef readonly Pool mem
+    cpdef readonly Extractor extractor
+    cpdef readonly LinearModel model
+
+    cpdef readonly TagType tag_type
+    cpdef readonly list tag_names
+
+    cdef class_t _guess
+    cdef atom_t* _context
+    cdef feat_t* _feats
+    cdef weight_t* _values
+    cdef weight_t* _scores
diff --git a/spacy/tagger.pyx b/spacy/tagger.pyx
new file mode 100644
index 000000000..55f46fa67
--- /dev/null
+++ b/spacy/tagger.pyx
@@ -0,0 +1,91 @@
+# cython: profile=True
+from os import path
+import os
+import shutil
+import random
+import codecs
+import gzip
+import json
+import cython
+
+
+from thinc.features cimport ConjFeat
+
+NULL_TAG = 0
+
+
+cdef class Tagger:
+    """Assign part-of-speech, named entity or supersense tags, using greedy
+    decoding.  The tagger reads its model and configuration from disk.
+    """
+    def __init__(self, model_dir):
+        self.mem = Pool()
+        cfg = json.load(path.join(model_dir, 'config.json'))
+        templates = cfg['templates']
+        self.tag_names = cfg['tag_names']
+        self.tag_type = cfg['tag_type']
+        self.model = LinearModel(len(self.tag_names))
+        if path.exists(path.join(model_dir, 'model')):
+            self.model.load(path.join(model_dir, 'model'))
+        self.extractor = Extractor(templates, [ConjFeat] * len(templates))
+
+        self._feats = <feat_t*>self.mem.alloc(self.extractor.n+1, sizeof(feat_t))
+        self._values = <weight_t*>self.mem.alloc(self.extractor.n+1, sizeof(weight_t))
+        self._scores = <weight_t*>self.mem.alloc(len(self.cfg.tags), sizeof(weight_t))
+        self._guess = NULL_TAG
+
+    cpdef int set_tags(self, Tokens tokens) except -1:
+        """Assign tags to a Tokens object.
+
+        >>> tokens = EN.tokenize(u'An example sentence.')
+        >>> assert tokens[0].pos == 'NO_TAG'
+        >>> EN.pos_tagger.set_tags(tokens)
+        >>> assert tokens[0].pos == 'DT'
+        """
+        cdef int i
+        for i in range(tokens.length):
+            tokens.set_tag(i, self.tag_type, self.predict(i, tokens))
+
+    cpdef class_t predict(self, int i, Tokens tokens) except 0:
+        """Predict the tag of tokens[i].  The tagger remembers the features and
+        prediction, in case you later call tell_answer.
+
+        >>> tokens = EN.tokenize(u'An example sentence.')
+        >>> tag = EN.pos_tagger.predict(0, tokens)
+        >>> assert tag == EN.pos_tagger.tag_id('DT') == 5
+        """
+        #if self.tag_type == POS:
+        #    _pos_feats.fill_context(self._context, i, tokens)
+        self.extractor.extract(self._feats, self._values, self._context, NULL)
+        self._guess = self.model.score(self._scores, self._feats, self._values)
+        return self._guess
+
+    cpdef int tell_answer(self, class_t gold) except -1:
+        """Provide the correct tag for the word the tagger was last asked to predict.
+        During Tagger.predict, the tagger remembers the features and prediction
+        for the example. These are used to calculate a weight update given the
+        correct label.
+
+        >>> tokens = EN.tokenize('An example sentence.')
+        >>> guess = EN.pos_tagger.predict(1, tokens)
+        >>> JJ = EN.pos_tagger.tag_id('JJ')
+        >>> JJ
+        7
+        >>> EN.pos_tagger.tell_answer(JJ)
+        """
+        cdef class_t guess = self._guess
+        if gold == guess or gold == NULL_TAG:
+            self.model.update({})
+            return 0
+        counts = {guess: {}, gold: {}}
+        self.extractor.count(counts[gold], self._feats, 1)
+        self.extractor.count(counts[guess], self._feats, -1)
+        self.model.update(counts)
+
+    def tag_id(self, object tag_name):
+        """Encode tag_name into a tag ID integer."""
+        tag_id = self.tag_names.index(tag_name)
+        if tag_id == -1:
+            tag_id = len(self.tag_names)
+            self.tag_names.append(tag_name)
+        return tag_id