From c10f3579c66a3cabad0b9baecb8f9fc9a579ed69 Mon Sep 17 00:00:00 2001
From: Filip Gralinski <filipg@amu.edu.pl>
Date: Wed, 4 Oct 2017 21:56:17 +0200
Subject: [PATCH] fix BLEU for empty output

---
 src/GEval/Core.hs                                  | 1 +
 test/Spec.hs                                       | 2 ++
 test/bleu-empty/bleu-empty-solution/test-A/out.tsv | 4 ++++
 test/bleu-empty/bleu-empty/config.txt              | 1 +
 test/bleu-empty/bleu-empty/test-A/expected.tsv     | 4 ++++
 5 files changed, 12 insertions(+)
 create mode 100644 test/bleu-empty/bleu-empty-solution/test-A/out.tsv
 create mode 100644 test/bleu-empty/bleu-empty/config.txt
 create mode 100644 test/bleu-empty/bleu-empty/test-A/expected.tsv

diff --git a/src/GEval/Core.hs b/src/GEval/Core.hs
index 307ca0b..1e97b1c 100644
--- a/src/GEval/Core.hs
+++ b/src/GEval/Core.hs
@@ -226,6 +226,7 @@ gevalCore' BLEU _ = gevalCoreWithoutInput (Prelude.map Prelude.words . DLS.split
         bleuFuse (a1, a2, a3, a4, a5, a6, a7, a8, a9) (b1, b2, b3, b4, b5, b6, b7, b8, b9) = (a1+b1, a2+b2, a3+b3, a4+b4, a5+b5, a6+b6, a7+b7, a8+b8, a9+b9)
         brevityPenalty c r
           | c >= r = 1.0
+          | c == 0 && r > 0 = 0.0
           | otherwise = exp (1.0 - (r /. c))
 
 gevalCore' Accuracy _ = gevalCoreWithoutInput strip strip hitOrMiss averageC id
diff --git a/test/Spec.hs b/test/Spec.hs
index 74421cc..fbaa0e6 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -48,6 +48,8 @@ main = hspec $ do
       runGEvalTest "bleu-complex" `shouldReturnAlmost` 0.6211
     it "perfect translation" $
       runGEvalTest "bleu-perfect" `shouldReturnAlmost` 1.0000
+    it "empty translation" $
+      runGEvalTest "bleu-empty" `shouldReturnAlmost` 0.0000
   describe "Accuracy" $ do
     it "simple example" $
       runGEvalTest "accuracy-simple" `shouldReturnAlmost` 0.6
diff --git a/test/bleu-empty/bleu-empty-solution/test-A/out.tsv b/test/bleu-empty/bleu-empty-solution/test-A/out.tsv
new file mode 100644
index 0000000..fd40910
--- /dev/null
+++ b/test/bleu-empty/bleu-empty-solution/test-A/out.tsv
@@ -0,0 +1,4 @@
+
+
+
+
diff --git a/test/bleu-empty/bleu-empty/config.txt b/test/bleu-empty/bleu-empty/config.txt
new file mode 100644
index 0000000..32a1b93
--- /dev/null
+++ b/test/bleu-empty/bleu-empty/config.txt
@@ -0,0 +1 @@
+--metric BLEU
diff --git a/test/bleu-empty/bleu-empty/test-A/expected.tsv b/test/bleu-empty/bleu-empty/test-A/expected.tsv
new file mode 100644
index 0000000..25af67b
--- /dev/null
+++ b/test/bleu-empty/bleu-empty/test-A/expected.tsv
@@ -0,0 +1,4 @@
+Litwo, Ojczyzno moja! ty jesteś jak zdrowie;
+Ile cię trzeba cenić, ten tylko się dowie,
+Kto cię stracił. Dziś piękność twą w całej ozdobie
+Widzę i opisuję, bo tęsknię po tobie.