Quotient filter: a first test case (no implementation yet)

Author: thomasmueller

fastfilter/src/test/java/org/fastfilter/quotient/InsertOrderTest.java

@@ -0,0 +1,78 @@
+package org.fastfilter.quotient;
+
+import java.util.Arrays;
+
+public class InsertOrderTest {
+    public static void main(String... args) {
+        for(int size = 1_000_000; size <= 100_000_000; size *= 10) {
+            long[] keys = new long[size];
+            for(int i=0; i<size; i++) {
+                // guaranteed unique
+                keys[i] = hash64(i, 0);
+            }
+            System.out.print(size + " unsorted keys:");
+            for (double fillRatePercent = 99; fillRatePercent > 50; fillRatePercent--) {
+                boolean success = test(keys, fillRatePercent / 100.0);
+                if (success) {
+                    System.out.println(" success at fill rate " + fillRatePercent + "%");
+                    break;
+                }
+            }
+            Arrays.sort(keys);
+            System.out.print(size + " sorted keys:");
+            for (double fillRatePercent = 99; fillRatePercent > 50; fillRatePercent--) {
+                boolean success = test(keys, fillRatePercent / 100.0);
+                if (success) {
+                    System.out.println(" success at fill rate " + fillRatePercent + "%");
+                    break;
+                }
+            }
+        }
+    }
+
+    public static long hash64(long x, long seed) {
+        x += seed;
+        x = (x ^ (x >>> 33)) * 0xff51afd7ed558ccdL;
+        x = (x ^ (x >>> 33)) * 0xc4ceb9fe1a85ec53L;
+        x = x ^ (x >>> 33);
+        return x;
+    }
+
+    public static int reduce(int hash, int n) {
+        // http://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+        return (int) (((hash & 0xffffffffL) * n) >>> 32);
+    }
+
+    static boolean test(long[] keys, double fillRate) {
+        // System.out.println("fillRate " + fillRate);
+        int slotsPerBlock = 48;
+        int slots = (int) (keys.length / fillRate);
+        int blocks = (slots + slotsPerBlock) / slotsPerBlock;
+        slots = blocks * slotsPerBlock;
+
+        int[] used = new int[blocks];
+        for (int i = 0; i < keys.length; i++) {
+//            if ((i % (keys.length / 10)) == 0) {
+//                for (int j = 0; j < used.length; j += 10) {
+//                    System.out.print(used[j] / 10);
+//                }
+//                System.out.println();
+//            }
+            long k = keys[i];
+            int index = reduce((int) k, blocks);
+            int index2 = reduce((int) (k >> 32), blocks);
+            if (used[index] < used[index2]) {
+                used[index]++;
+                if (used[index] > slotsPerBlock) {
+                    return false;
+                }
+            } else {
+                used[index2]++;
+                if (used[index2] > slotsPerBlock) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}