common/bloom_filter: unit tests

Fun facts:

- fpp = false positive probability
- fpp is a function of insert count only
- at .1% fpp, we pay about 2 bytes per insert
- at 1-2% fpp, we pay about 1 byte per insert
- at 15% fpp, we pay about .5 bytes per insert

Signed-off-by: Sage Weil <sage@inktank.com>

src/common/bloom_filter.hpp

@@ -26,6 +26,7 @@
 #include <algorithm>
 #include <cmath>
 #include <limits>
+#include <list>
 #include <string>
 #include <vector>
 
@@ -470,7 +471,7 @@ public:
    void encode(bufferlist& bl) const;
    void decode(bufferlist::iterator& bl);
    void dump(Formatter *f) const;
-   static void generate_test_instances(list<bloom_filter*>& ls);
+   static void generate_test_instances(std::list<bloom_filter*>& ls);
 };
 WRITE_CLASS_ENCODER(bloom_filter)
 

src/test/Makefile.am

@@ -258,6 +258,11 @@ unittest_addrs_CXXFLAGS = $(UNITTEST_CXXFLAGS)
 unittest_addrs_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL)
 check_PROGRAMS += unittest_addrs
 
+unittest_bloom_filter_SOURCES = test/common/test_bloom_filter.cc
+unittest_bloom_filter_CXXFLAGS = $(UNITTEST_CXXFLAGS)
+unittest_bloom_filter_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL)
+check_PROGRAMS += unittest_bloom_filter
+
 unittest_sharedptr_registry_SOURCES = test/common/test_sharedptr_registry.cc
 unittest_sharedptr_registry_CXXFLAGS = $(UNITTEST_CXXFLAGS)
 unittest_sharedptr_registry_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL)

src/test/common/test_bloom_filter.cc

@@ -0,0 +1,62 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2013 Inktank <info@inktank.com>
+ *
+ * LGPL2.1 (see COPYING-LGPL2.1) or later
+ */
+
+#include <iostream>
+#include <gtest/gtest.h>
+
+#include "include/stringify.h"
+#include "common/bloom_filter.hpp"
+
+TEST(BloomFilter, Basic) {
+  bloom_filter bf(10, .1, 1);
+  bf.insert("foo");
+  bf.insert("bar");
+
+  ASSERT_TRUE(bf.contains("foo"));
+  ASSERT_TRUE(bf.contains("bar"));
+}
+
+TEST(BloomFilter, Sweep) {
+  std::cout << "# max\tfpp\tactual\tsize\tB/insert" << std::endl;
+  for (int ex = 3; ex < 12; ex++) {
+    for (float fpp = .001; fpp < .5; fpp *= 2.0) {
+      int max = 2 << ex;
+      bloom_filter bf(max, fpp, 1);
+      bf.insert("foo");
+      bf.insert("bar");
+
+      ASSERT_TRUE(bf.contains("foo"));
+      ASSERT_TRUE(bf.contains("bar"));
+
+      for (int n = 0; n < max; n++)
+	bf.insert("ok" + stringify(n));
+
+      int test = max * 100;
+      int hit = 0;
+      for (int n = 0; n < test; n++)
+	if (bf.contains("asdf" + stringify(n)))
+	  hit++;
+
+      ASSERT_TRUE(bf.contains("foo"));
+      ASSERT_TRUE(bf.contains("bar"));
+
+      double actual = (double)hit / (double)test;
+
+      bufferlist bl;
+      ::encode(bf, bl);
+
+      double byte_per_insert = (double)bl.length() / (double)max;
+
+      std::cout << max << "\t" << fpp << "\t" << actual << "\t" << bl.length() << "\t" << byte_per_insert << std::endl;
+      ASSERT_TRUE(actual < fpp * 10);
+
+    }
+  }
+}