From 98e13188c40adf13b73ca994d3410f3e87d20355 Mon Sep 17 00:00:00 2001
From: Victor Chahuneau <vchahune@cs.cmu.edu>
Date: Mon, 4 Jun 2012 02:16:59 -0400
Subject: Python module: initial version

---
 python/cdec/scfg/features.py | 62 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 python/cdec/scfg/features.py

(limited to 'python/cdec/scfg/features.py')

diff --git a/python/cdec/scfg/features.py b/python/cdec/scfg/features.py
new file mode 100644
index 00000000..6419cdd8
--- /dev/null
+++ b/python/cdec/scfg/features.py
@@ -0,0 +1,62 @@
+from __future__ import division
+import math
+import sym
+
+def contextless(feature):
+    feature.compute_contextless_score = feature
+    return feature
+
+MAXSCORE = 99
+
+def EgivenF(fphrase, ephrase, paircount, fcount, fsample_count): # p(e|f)
+    return -math.log10(paircount/fcount)
+
+def CountEF(fphrase, ephrase, paircount, fcount, fsample_count):
+    return math.log10(1 + paircount)
+
+def SampleCountF(fphrase, ephrase, paircount, fcount, fsample_count):
+    return math.log10(1 + fsample_count)
+
+def EgivenFCoherent(fphrase, ephrase, paircount, fcount, fsample_count):
+    prob = paircount/fsample_count
+    return -math.log10(prob) if prob > 0 else MAXSCORE
+
+def CoherenceProb(fphrase, ephrase, paircount, fcount, fsample_count):
+    return -math.log10(fcount/fsample_count)
+
+def MaxLexEgivenF(ttable):
+    def feature(fphrase, ephrase, paircount, fcount, fsample_count):
+        fwords = [sym.tostring(w) for w in fphrase if not sym.isvar(w)] + ['NULL']
+        ewords = (sym.tostring(w) for w in ephrase if not sym.isvar(w))
+        def score():
+            for e in ewords:
+              maxScore = max(ttable.get_score(f, e, 0) for f in fwords)
+              yield -math.log10(maxScore) if maxScore > 0 else MAXSCORE
+        return sum(score())
+    return feature
+
+def MaxLexFgivenE(ttable):
+    def feature(fphrase, ephrase, paircount, fcount, fsample_count):
+        fwords = (sym.tostring(w) for w in fphrase if not sym.isvar(w))
+        ewords = [sym.tostring(w) for w in ephrase if not sym.isvar(w)] + ['NULL']
+        def score():
+            for f in fwords:
+              maxScore = max(ttable.get_score(f, e, 1) for e in ewords)
+              yield -math.log10(maxScore) if maxScore > 0 else MAXSCORE
+        return sum(score())
+    return feature
+
+def IsSingletonF(fphrase, ephrase, paircount, fcount, fsample_count):
+    return (fcount == 1)
+
+def IsSingletonFE(fphrase, ephrase, paircount, fcount, fsample_count):
+    return (paircount == 1)
+
+def IsNotSingletonF(fphrase, ephrase, paircount, fcount, fsample_count):
+    return (fcount > 1)
+
+def IsNotSingletonFE(fphrase, ephrase, paircount, fcount, fsample_count):
+    return (paircount > 1)
+
+def IsFEGreaterThanZero(fphrase, ephrase, paircount, fcount, fsample_count):
+    return (paircount > 0.01)
-- 
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