diff --git a/Seq2SeqSharp/Corpus/ParallelCorpus.cs b/Seq2SeqSharp/Corpus/ParallelCorpus.cs
index 90ed49e..ddd93eb 100644
--- a/Seq2SeqSharp/Corpus/ParallelCorpus.cs
+++ b/Seq2SeqSharp/Corpus/ParallelCorpus.cs
@@ -341,6 +341,11 @@ public void PrepareDataSet()
                 Logger.WriteLine(Logger.Level.debug, $"Start to sort and shuffle data set by length.");
 
                 m_sortedIndexedDataSetFilePath = tmpDataSetFilePath + ".sorted";
+
+#if DEBUG
+                string tmp_sortedIndexedDataSetFilePath = tmpDataSetFilePath + ".sorted.txt";
+                using (StreamWriter bwt = new StreamWriter(new FileStream(tmp_sortedIndexedDataSetFilePath, FileMode.Create, FileAccess.Write, FileShare.None, 40960000)))
+#endif
                 using (BinaryWriter bw = new BinaryWriter(new FileStream(m_sortedIndexedDataSetFilePath, FileMode.Create, FileAccess.Write, FileShare.None, 40960000)))
                 using (MemoryMappedFile mmf = MemoryMappedFile.CreateFromFile(tmpDataSetFilePath))
                 using (MemoryMappedViewStream mms = mmf.CreateViewStream())
@@ -383,6 +388,12 @@ public void PrepareDataSet()
                             bw.Write(String.Join("\n", srcLines));
                             bw.Write(String.Join("\n", tgtLines));
 
+#if DEBUG
+                            bwt.WriteLine(sentSize);
+                            bwt.WriteLine(String.Join("\n", srcLines));
+                            bwt.WriteLine(String.Join("\n", tgtLines));
+#endif
+
                             m_batchNumInTotal++;
                             if (m_batchNumInTotal % 10000 == 0)
                             {