Merge pull request #4 from codahale/pr/CASSANDRA-1220

Improve BloomFilter efficiency

Author: abramsm

src/main/java/com/clearspring/analytics/stream/membership/BloomCalculations.java

@@ -36,7 +36,7 @@ public class BloomCalculations {
     private static final int[] optKPerBuckets =
             new int[]{1, // dummy K for 0 buckets per element
                       1, // dummy K for 1 buckets per element
-                      1, 2, 3, 3, 4, 5, 5, 6, 7, 8, 8, 8, 8, 8};
+                      1, 2, 3, 3, 4, 5, 5, 6, 7, 8, 8, 9, 10, 10, 11, 12, 12, 13, 14};
 
     /**
      * In the following table, the row 'i' shows false positive rates if i buckets
@@ -49,19 +49,24 @@ public class BloomCalculations {
         {1.0}, // dummy row representing 0 buckets per element
         {1.0, 1.0}, // dummy row representing 1 buckets per element
         {1.0, 0.393,  0.400},
-        {1.0, 0.283,  0.237,  0.253},
-        {1.0, 0.221,  0.155,  0.147,   0.160},
-        {1.0, 0.181,  0.109,  0.092,   0.092,   0.101}, // 5
-        {1.0, 0.154,  0.0804, 0.0609,  0.0561,  0.0578,  0.0638},
-        {1.0, 0.133,  0.0618, 0.0423,  0.0359,  0.0347,  0.0364},
-        {1.0, 0.118,  0.0489, 0.0306,  0.024,   0.0217,  0.0216,  0.0229},
-        {1.0, 0.105,  0.0397, 0.0228,  0.0166,  0.0141,  0.0133,  0.0135,  0.0145}, // 9
-        {1.0, 0.0952, 0.0329, 0.0174,  0.0118,  0.00943, 0.00844, 0.00819, 0.00846},
-        {1.0, 0.0869, 0.0276, 0.0136,  0.00864, 0.0065,  0.00552, 0.00513, 0.00509},
-        {1.0, 0.08,   0.0236, 0.0108,  0.00646, 0.00459, 0.00371, 0.00329, 0.00314},
-        {1.0, 0.074,  0.0203, 0.00875, 0.00492, 0.00332, 0.00255, 0.00217, 0.00199},
-        {1.0, 0.0689, 0.0177, 0.00718, 0.00381, 0.00244, 0.00179, 0.00146, 0.00129},
-        {1.0, 0.0645, 0.0156, 0.00596, 0.003,   0.00183, 0.00128, 0.001,   0.000852} // 15
+        {1.0, 0.283,  0.237,   0.253},
+        {1.0, 0.221,  0.155,   0.147,   0.160},
+        {1.0, 0.181,  0.109,   0.092,   0.092,   0.101}, // 5
+        {1.0, 0.154,  0.0804,  0.0609,  0.0561,  0.0578,   0.0638},
+        {1.0, 0.133,  0.0618,  0.0423,  0.0359,  0.0347,   0.0364},
+        {1.0, 0.118,  0.0489,  0.0306,  0.024,   0.0217,   0.0216,   0.0229},
+        {1.0, 0.105,  0.0397,  0.0228,  0.0166,  0.0141,   0.0133,   0.0135,   0.0145},
+        {1.0, 0.0952, 0.0329,  0.0174,  0.0118,  0.00943,  0.00844,  0.00819,  0.00846}, // 10
+        {1.0, 0.0869, 0.0276,  0.0136,  0.00864, 0.0065,   0.00552,  0.00513,  0.00509},
+        {1.0, 0.08,   0.0236,  0.0108,  0.00646, 0.00459,  0.00371,  0.00329,  0.00314},
+        {1.0, 0.074,  0.0203,  0.00875, 0.00492, 0.00332,  0.00255,  0.00217,  0.00199,  0.00194},
+        {1.0, 0.0689, 0.0177,  0.00718, 0.00381, 0.00244,  0.00179,  0.00146,  0.00129,  0.00121,  0.0012},
+        {1.0, 0.0645, 0.0156,  0.00596, 0.003,   0.00183,  0.00128,  0.001,    0.000852, 0.000775, 0.000744}, // 15
+        {1.0, 0.0606, 0.0138,  0.005,   0.00239, 0.00139,  0.000935, 0.000702, 0.000574, 0.000505, 0.00047,  0.000459},
+        {1.0, 0.0571, 0.0123,  0.00423, 0.00193, 0.00107,  0.000692, 0.000499, 0.000394, 0.000335, 0.000302, 0.000287, 0.000284},
+        {1.0, 0.054,  0.0111,  0.00362, 0.00158, 0.000839, 0.000519, 0.00036,  0.000275, 0.000226, 0.000198, 0.000183, 0.000176},
+        {1.0, 0.0513, 0.00998, 0.00312, 0.0013,  0.000663, 0.000394, 0.000264, 0.000194, 0.000155, 0.000132, 0.000118, 0.000111, 0.000109},
+        {1.0, 0.0488, 0.00906, 0.0027,  0.00108, 0.00053,  0.000303, 0.000196, 0.00014,  0.000108, 8.89e-05, 7.77e-05, 7.12e-05, 6.79e-05, 6.71e-05} // 20
     };  // the first column is a dummy column representing K=0.
 
     /**