Index: MoreLikeThis.java
===================================================================
--- MoreLikeThis.java	(revision 766250)
+++ MoreLikeThis.java	(working copy)
@@ -148,6 +148,12 @@
 public final class MoreLikeThis {
 
 	/**
+     * Default term frequency cache
+     * @see #setCache
+     */
+     public static final boolean DEFAULT_CACHE = false;
+    
+    /**
 	 * Default maximum number of tokens to parse in each example doc field that is not stored with TermVector support.
 	 * @see #getMaxNumTokensParsed
 	 */
@@ -254,8 +260,12 @@
 	 */
 	private int maxNumTokensParsed=DEFAULT_MAX_NUM_TOKENS_PARSED;   
     
+    /**
+     * Whether or not to cache term frequencies
+     */
+    private boolean _useCache = DEFAULT_CACHE;
+    private static Map<String,Map<String,Integer>> _cache = new HashMap<String,Map<String,Integer>>();
 
-
     /**
      * Ignore words if less than this len.
      */
@@ -507,6 +517,13 @@
 	}
 
 
+    /**
+     * @param useCache Whether or not to cache Term frequencies
+     */
+    public void setCache( boolean useCache )
+    {
+        _useCache = useCache;
+    }
 
 
     /**
@@ -627,10 +644,26 @@
             // go through all the fields and find the largest document frequency
             String topField = fieldNames[0];
             int docFreq = 0;
-            for (int i = 0; i < fieldNames.length; i++) {
-                int freq = ir.docFreq(new Term(fieldNames[i], word));
-                topField = (freq > docFreq) ? fieldNames[i] : topField;
-                docFreq = (freq > docFreq) ? freq : docFreq;
+            for (int i = 0; i < fieldNames.length; i++)
+            {
+                Integer freq;
+                if ( _useCache )
+                {
+                    // Check the term frequency cache 
+                    if ( _cache.get(fieldNames[i]) == null ) _cache.put( fieldNames[i], new HashMap<String,Integer>() );
+                    freq = _cache.get(fieldNames[i]).get(word);
+                    if ( freq == null )
+                    {
+                        freq = ir.docFreq(new Term(fieldNames[i], word));
+                        _cache.get(fieldNames[i]).put( word, freq );
+                    }
+                }
+                else
+                {
+	                freq = ir.docFreq(new Term(fieldNames[i], word));
+	            }
+	            topField = (freq > docFreq) ? fieldNames[i] : topField;
+		        docFreq = (freq > docFreq) ? freq : docFreq;
             }
 
             if (minDocFreq > 0 && docFreq < minDocFreq) {