fix simulator's bloom filter table minumum sizing

The table index is calculated by shifting the hashed value. As no
modulus is applied, the negation bit may lead the minimum index
to be 0 or 1, while the table size is one. Either the index has
to be modulated (via a mask) or the smallest table should be 2
to avoid this off-by-one error. Increasing the minimum allows for
simplifying the code.

caffeine/build.gradle

@@ -48,6 +48,7 @@ dependencies {
   javaAgent libraries.jamm
 
   jmh libraries.jamm
+  jmh libraries.guava
   jmh libraries.tcache
   jmh libraries.cache2k
   jmh libraries.ehcache3

caffeine/src/jmh/java/com/github/benmanes/caffeine/cache/impl/Cache2k.java

@@ -28,7 +28,7 @@ public final class Cache2k<K, V> implements BasicCache<K, V> {
 
   @SuppressWarnings("unchecked")
   public Cache2k(int maximumSize) {
-    cache = Cache2kBuilder.forUnknownTypes()
+    cache = (Cache<K, V>) Cache2kBuilder.forUnknownTypes()
         .entryCapacity(maximumSize)
         .eternal(true)
         .build();

gradle/dependencies.gradle

@@ -26,7 +26,7 @@
 ext {
   versions = [
     akka: '2.6.10',
-    cache2k: '1.9.1.Alpha',
+    cache2k: '1.9.3.Alpha',
     checkerFramework: '3.7.1',
     coherence: '20.06',
     collision: '0.3.3',

gradle/jmh.gradle

@@ -9,10 +9,6 @@ idea.module {
   scopes.PROVIDED.plus += [ configurations.jmh ]
 }
 
-plugins.withType(EclipsePlugin) {
-  project.eclipse.classpath.plusConfigurations += [ configurations.jmh ]
-}
-
 eclipse.classpath.file.whenMerged {
   entries.find { it.path == 'src/jmh/java' }.entryAttributes['test'] = 'true'
 }
@@ -57,9 +53,9 @@ jmh {
   resultsFile = file("${buildDir}/reports/jmh/results.json")
 
   jvmArgs = '-server -Xmx2G -XX:+UseG1GC -XX:-UseBiasedLocking'
-  warmupIterations = 10
+  warmupIterations = 3
   failOnError = true
-  iterations = 10
+  iterations = 3
   forceGC = true
   fork = 1
 }

simulator/src/main/java/com/github/benmanes/caffeine/cache/simulator/membership/bloom/BloomFilter.java

@@ -44,6 +44,12 @@ public final class BloomFilter implements Membership {
   int tableShift;
   long[] table;
 
+  /**
+   * Creates a lazily initialized membership sketch, requiring {@link #ensureCapacity} be called
+   * when the expected number of insertions and the false positive probability have been determined.
+   */
+  public BloomFilter() {}
+
   /**
    * Creates a membership sketch based on the expected number of insertions and the false positive
    * probability.
@@ -61,18 +67,15 @@ public BloomFilter(Config config) {
    * @param expectedInsertions the number of expected insertions
    * @param fpp the false positive probability, where 0.0 > fpp < 1.0
    */
-  void ensureCapacity(@NonNegative long expectedInsertions, @NonNegative double fpp) {
+  public void ensureCapacity(@NonNegative long expectedInsertions, @NonNegative double fpp) {
     checkArgument(expectedInsertions >= 0);
     checkArgument(fpp > 0 && fpp < 1);
 
     double optimalBitsFactor = -Math.log(fpp) / (Math.log(2) * Math.log(2));
     int optimalNumberOfBits = (int) (expectedInsertions * optimalBitsFactor);
-    int optimalSize = optimalNumberOfBits >>> BITS_PER_LONG_SHIFT;
+    int optimalSize = Math.max(2, optimalNumberOfBits >>> BITS_PER_LONG_SHIFT);
     if ((table != null) && (table.length >= optimalSize)) {
       return;
-    } else if (optimalSize == 0) {
-      tableShift = Integer.SIZE - 1;
-      table = new long[2];
     } else {
       int powerOfTwoShift = Integer.SIZE - Integer.numberOfLeadingZeros(optimalSize - 1);
       tableShift = Integer.SIZE - powerOfTwoShift;

simulator/src/main/java/com/github/benmanes/caffeine/cache/simulator/parser/Rewriter.java

@@ -61,7 +61,6 @@ public final class Rewriter implements Runnable {
   private OutputFormat outputFormat;
 
   @Override
-  @SuppressWarnings("PMD.ForLoopCanBeForeach")
   public void run() {
     Stopwatch stopwatch = Stopwatch.createStarted();
     try (OutputStream output = new BufferedOutputStream(Files.newOutputStream(outputFile));

simulator/src/test/java/com/github/benmanes/caffeine/cache/simulator/admission/bloom/MembershipTest.java

@@ -22,15 +22,18 @@
 import static org.hamcrest.Matchers.lessThan;
 
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
+import java.util.stream.IntStream;
 
 import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;
 
 import com.github.benmanes.caffeine.cache.simulator.membership.FilterType;
 import com.github.benmanes.caffeine.cache.simulator.membership.Membership;
+import com.github.benmanes.caffeine.cache.simulator.membership.bloom.BloomFilter;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.jakewharton.fliptables.FlipTable;
@@ -74,6 +77,18 @@ public void bloomFilterTest(FilterType filterType) {
     }
   }
 
+  @Test(dataProvider = "ensureCapacity")
+  public void caffeine_ensureCapacity(int expectedInsertions, double fpp) {
+    BloomFilter filter = new BloomFilter();
+    filter.ensureCapacity(expectedInsertions, fpp);
+    filter.put(-1);
+  }
+
+  @DataProvider(name = "ensureCapacity")
+  public Iterator<Object[]> providesExpectedInsertions() {
+    return IntStream.range(0,  25).boxed().map(i -> new Object[] { i, FPP }).iterator();
+  }
+
   @DataProvider(name = "filterTypes")
   public Object[] providesFilterTypes() {
     return FilterType.values();