Switch infer spaces from doubles to floats

This change will consume about half the memory that the previous
doubles consumed. The change in precision shouldn't affect the results
of word splitting.

src/metabase/util/infer_spaces.clj

@@ -20,7 +20,7 @@
   (let [log-count (Math/log (count words))]
     (into (sorted-map)
           (map-indexed (fn [idx word]
-                         [(hash word) (Math/log (* (inc idx) log-count))])
+                         [(hash word) (float (Math/log (* (inc idx) log-count)))])
                        words))))
 
 ;; # Build arrays for a cost lookup, assuming Zipf's law and cost = -math.log(probability).
@@ -35,9 +35,9 @@
     "Array of word hash values, ordered by that hash value"
     (int-array (keys sorted-words)))
 
-  (def ^:private ^"[D" word-cost
-    "Array of word cost doubles, ordered by the hash value for that word"
-    (double-array (vals sorted-words)))
+  (def ^:private ^"[F" word-cost
+    "Array of word cost floats, ordered by the hash value for that word"
+    (float-array (vals sorted-words)))
 
   ;; maxword = max(len(x) for x in words)
   (def ^:private max-word
@@ -97,7 +97,7 @@
   [input]
   (let [s (s/lower-case input)
         cost (build-cost-array s)]
-    (loop [i (double (count s))
+    (loop [i (float (count s))
            out []]
       (if-not (pos? i)
         (reverse out)