[python] MT evaluation

1 files changed, 116 insertions, 0 deletions

diff --git a/python/src/mteval.pxi b/python/src/mteval.pxi
new file mode 100644
index 00000000..dabdf927
--- /dev/null
+++ b/python/src/mteval.pxi
@@ -0,0 +1,116 @@
+cimport mteval
+
+cdef char* as_str(sentence, error_msg='Cannot convert type %s to str'):
+    cdef bytes ret
+    if isinstance(sentence, unicode):
+        ret = sentence.encode('utf8')
+    elif isinstance(sentence, str):
+        ret = sentence
+    else:
+        raise TypeError(error_msg % type(sentence))
+    return ret
+
+cdef class Candidate:
+    cdef mteval.Candidate* candidate
+    cdef public float score
+
+    property words:
+        def __get__(self):
+            return unicode(GetString(self.candidate.ewords).c_str(), encoding='utf8')
+
+    property fmap:
+        def __get__(self):
+            cdef SparseVector fmap = SparseVector()
+            fmap.vector = new FastSparseVector[weight_t](self.candidate.fmap)
+            return fmap
+
+cdef class SufficientStats:
+    cdef mteval.SufficientStats* stats
+    cdef mteval.EvaluationMetric* metric
+
+    def __dealloc__(self):
+        del self.stats
+
+    property score:
+        def __get__(self):
+            return self.metric.ComputeScore(self.stats[0])
+
+    property detail:
+        def __get__(self):
+            return self.metric.DetailedScore(self.stats[0]).c_str()
+
+    def __len__(self):
+        return self.stats.size()
+
+    def __iter__(self):
+        for i in range(len(self)):
+            yield self.stats[0][i]
+
+    def __iadd__(SufficientStats self, SufficientStats other):
+        self.stats[0] += other.stats[0]
+        return self
+
+    def __add__(SufficientStats x, SufficientStats y):
+        cdef SufficientStats result = SufficientStats()
+        result.stats = new mteval.SufficientStats(mteval.add(x.stats[0], y.stats[0]))
+        result.metric = x.metric
+        return result
+
+cdef class SegmentEvaluator:
+    cdef shared_ptr[mteval.SegmentEvaluator]* scorer
+    cdef mteval.EvaluationMetric* metric
+    
+    def __dealloc__(self):
+        del self.scorer
+
+    def evaluate(self, sentence):
+        cdef vector[WordID] hyp
+        cdef SufficientStats sf = SufficientStats()
+        sf.metric = self.metric
+        sf.stats = new mteval.SufficientStats()
+        ConvertSentence(string(as_str(sentence.strip())), &hyp)
+        self.scorer.get().Evaluate(hyp, sf.stats)
+        return sf
+
+    def candidate_set(self, Hypergraph hypergraph, unsigned k):
+        cdef mteval.CandidateSet* cs = new mteval.CandidateSet()
+        cs.AddKBestCandidates(hypergraph.hg[0], k, self.scorer.get())
+        cdef Candidate candidate
+        cdef unsigned i
+        for i in range(cs.size()):
+            candidate = Candidate()
+            candidate.candidate = &cs[0][i]
+            candidate.score = self.metric.ComputeScore(cs[0][i].eval_feats)
+            yield candidate
+        del cs
+
+cdef class Scorer:
+    cdef string* name
+
+    def __cinit__(self, char* name):
+        self.name = new string(name)
+    
+    def __call__(self, refs):
+        cdef mteval.EvaluationMetric* metric = mteval.Instance(self.name[0])
+        if isinstance(refs, unicode) or isinstance(refs, str):
+            refs = [refs]
+        cdef vector[vector[WordID]]* refsv = new vector[vector[WordID]]()
+        cdef vector[WordID]* refv
+        cdef bytes ref_str
+        for ref in refs:
+            refv = new vector[WordID]()
+            ConvertSentence(string(as_str(ref.strip())), refv)
+            refsv.push_back(refv[0])
+            del refv
+        cdef unsigned i
+        cdef SegmentEvaluator evaluator = SegmentEvaluator()
+        evaluator.metric = metric
+        evaluator.scorer = new shared_ptr[mteval.SegmentEvaluator](metric.CreateSegmentEvaluator(refsv[0]))
+        del refsv # in theory should not delete but store in SegmentEvaluator
+        return evaluator
+
+    def __str__(self):
+        return self.name.c_str()
+
+BLEU = Scorer('IBM_BLEU')
+TER = Scorer('TER')