svn commit: r1388403 - /mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java

[srowen]

Author: srowen
Date: Fri Sep 21 10:16:00 2012
New Revision: 1388403

URL: http://svn.apache.org/viewvc?rev=1388403&view=rev
Log:
Prevent NaN in corner case of nDCG calculation

Modified:
    
mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java

Modified: 
mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java
URL: 
http://svn.apache.org/viewvc/mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java?rev=1388403&r1=1388402&r2=1388403&view=diff
==============================================================================
--- 
mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java
 (original)
+++ 
mahout/trunk/core/src/main/java/org/apache/mahout/cf/taste/impl/eval/GenericRecommenderIRStatsEvaluator.java
 Fri Sep 21 10:16:00 2012
@@ -191,7 +191,9 @@ public final class GenericRecommenderIRS
           idealizedGain += discount;
         }
       }
-      nDCG.addDatum(cumulativeGain / idealizedGain);
+      if (idealizedGain > 0.0) {
+        nDCG.addDatum(cumulativeGain / idealizedGain);
+      }
       
       // Reach
       numUsersRecommendedFor++;