Issue ReactiveX#7 RingBitSet optimisation

* test coverage added + jacoco excludes for benchmark classes

* Issue ReactiveX#7 RingBitSet optimisation + benchmark results

* Issue ReactiveX#7 cleanup

Author: storozhukBM

README.adoc

@@ -240,7 +240,7 @@ static <T> Supplier<T> decorateSupplier(Supplier<T> supplier, CircuitBreaker cir
 The state of the CircuitBreaker changes from `CLOSED` to `OPEN` when the failure rate is above a (configurable) threshold.
 Then, all access to the backend is blocked for a (configurable) time duration. `CircuitBreaker::isCallPermitted()` throws a `CircuitBreakerOpenException`, if the CircuitBreaker is `OPEN`.
 
-The CircuitBreaker uses a Ring Bit Buffer in the `CLOSED` state to store the success or failure statuses of the calls. A successful call is stored as a `0` bit and a failed call is stored as a `1` bit. The Ring Bit Buffer has a (configurable) fixed-size. The Ring Bit Buffer uses internally a https://docs.oracle.com/javase/8/docs/api/java/util/BitSet.html[BitSet] to store the bits which is saving memory compared to a boolean array. The BitSet uses a long[] array to store the bits. That means the BitSet only needs an array of 16 long (64-bit) values to store the status of 1024 calls.
+The CircuitBreaker uses a Ring Bit Buffer in the `CLOSED` state to store the success or failure statuses of the calls. A successful call is stored as a `0` bit and a failed call is stored as a `1` bit. The Ring Bit Buffer has a (configurable) fixed-size. The Ring Bit Buffer uses internally a https://docs.oracle.com/javase/8/docs/api/java/util/BitSet.html[BitSet] like data structure to store the bits which is saving memory compared to a boolean array. The BitSet uses a long[] array to store the bits. That means the BitSet only needs an array of 16 long (64-bit) values to store the status of 1024 calls.
 
 image::src/docs/asciidoc/images/ring_buffer.jpg[Ring Bit Buffer]
 
@@ -279,7 +279,7 @@ So you can easily restrict not only network calls but your local in-memory opera
 
 == License
 
-Copyright 2016 Robert Winkler
+Copyright 2016 Robert Winkler and Bohdan Storozhuk
 
 Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
 

build.gradle

@@ -105,12 +105,6 @@ artifacts {
 
 cobertura {
     coverageFormats = ['html', 'xml']
-//    afterEvaluate {
-//        classDirectories = files(classDirectories.files.collect {
-//            fileTree(dir: it,
-//                    exclude: ['**/**Benchmark**'])
-//        })
-//    }
 }
 
 tasks.coveralls {

src/docs/asciidoc/usage_guide.adoc

@@ -342,7 +342,7 @@ static <T> Supplier<T> decorateSupplier(Supplier<T> supplier, CircuitBreaker cir
 The state of the CircuitBreaker changes from `CLOSED` to `OPEN` when the failure rate is above a (configurable) threshold.
 Then, all access to the backend is blocked for a (configurable) time duration. `CircuitBreaker::isCallPermitted()` throws a `CircuitBreakerOpenException`, if the CircuitBreaker is `OPEN`.
 
-The CircuitBreaker uses a Ring Bit Buffer in the `CLOSED` state to store the success or failure statuses of the calls. A successful call is stored as a `0` bit and a failed call is stored as a `1` bit. The Ring Bit Buffer has a (configurable) fixed-size. The Ring Bit Buffer uses internally a https://docs.oracle.com/javase/8/docs/api/java/util/BitSet.html[BitSet] to store the bits which is saving memory compared to a boolean array. The BitSet uses a long[] array to store the bits. That means the BitSet only needs an array of 16 long (64-bit) values to store the status of 1024 calls.
+The CircuitBreaker uses a Ring Bit Buffer in the `CLOSED` state to store the success or failure statuses of the calls. A successful call is stored as a `0` bit and a failed call is stored as a `1` bit. The Ring Bit Buffer has a (configurable) fixed-size. The Ring Bit Buffer uses internally a https://docs.oracle.com/javase/8/docs/api/java/util/BitSet.html[BitSet] like data structure to store the bits which is saving memory compared to a boolean array. The BitSet uses a long[] array to store the bits. That means the BitSet only needs an array of 16 long (64-bit) values to store the status of 1024 calls.
 
 image::images/ring_buffer.jpg[Ring Bit Buffer]
 

src/jmh/java/io/github/robwin/circuitbreaker/CircularBufferBenchmark.java

@@ -1,6 +1,6 @@
 /*
  *
- *  Copyright 2016 Robert Winkler
+ *  Copyright 2016 Robert Winkler and Bohdan Storozhuk
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -19,24 +19,38 @@
 package io.github.robwin.circuitbreaker;
 
 import io.github.robwin.circuitbreaker.internal.RingBitSet;
-import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Group;
+import org.openjdk.jmh.annotations.GroupThreads;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
 
 import java.util.concurrent.TimeUnit;
 
 @State(Scope.Benchmark)
-@OutputTimeUnit(TimeUnit.MILLISECONDS)
-@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@BenchmarkMode(Mode.All)
 public class RingBitSetBenchmark {
 
-    private RingBitSet ringBitSet;
+    private static final int CAPACITY = 1000;
     private static final int ITERATION_COUNT = 10;
     private static final int WARMUP_COUNT = 10;
-    private static final int THREAD_COUNT = 10;
-    private static final int FORK_COUNT = 1;
+    private static final int THREAD_COUNT = 2;
+    private static final int FORK_COUNT = 2;
+
+    private RingBitSet ringBitSet;
 
     @Setup
     public void setUp() {
-        ringBitSet = new RingBitSet(1000);
+        ringBitSet = new RingBitSet(CAPACITY);
     }
 
     @Benchmark
@@ -45,18 +59,21 @@ public void setUp() {
     @GroupThreads(THREAD_COUNT)
     @Warmup(iterations = WARMUP_COUNT)
     @Measurement(iterations = ITERATION_COUNT)
-    public void setBits(){
-        ringBitSet.setNextBit(true);
-        ringBitSet.setNextBit(false);
+    public void concurrentSetBits(Blackhole bh) {
+        int firstCardinality = ringBitSet.setNextBit(true);
+        bh.consume(firstCardinality);
+        int secondCardinality = ringBitSet.setNextBit(false);
+        bh.consume(secondCardinality);
     }
 
     @Benchmark
     @Fork(value = FORK_COUNT)
     @Group("ringBitSet")
-    @GroupThreads(THREAD_COUNT)
+    @GroupThreads(1)
     @Warmup(iterations = WARMUP_COUNT)
     @Measurement(iterations = ITERATION_COUNT)
-    public int cardinality(){
-        return ringBitSet.cardinality();
+    public void concurrentCardinality(Blackhole bh) {
+        int cardinality = ringBitSet.cardinality();
+        bh.consume(cardinality);
     }
 }

src/jmh/java/io/github/robwin/circuitbreaker/RingBitSetBenchmark.java

@@ -0,0 +1,68 @@
+/*
+ *
+ *  Copyright 2016 Robert Winkler and Bohdan Storozhuk
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *
+ */
+package io.github.robwin.circuitbreaker.internal;
+
+/**
+ * {@link BitSetMod} is simplified version of {@link java.util.BitSet}.
+ * It has no dynamic allocation, expanding logic, boundary checks
+ * and it's set method returns previous bit state.
+ */
+class BitSetMod {
+
+    private final static int ADDRESS_BITS_PER_WORD = 6;
+    private final int size;
+    private final long[] words;
+
+
+    BitSetMod(final int capacity) {
+        int countOfWordsRequired = wordIndex(capacity - 1) + 1;
+        size = countOfWordsRequired << ADDRESS_BITS_PER_WORD;
+        words = new long[countOfWordsRequired];
+    }
+
+    /**
+     * Given a bit index, return word index containing it.
+     */
+    private static int wordIndex(int bitIndex) {
+        return bitIndex >> ADDRESS_BITS_PER_WORD;
+    }
+
+    /**
+     * Sets the bit at the specified index to value.
+     *
+     * @param bitIndex a bit index
+     * @return previous state of bitIndex that can be {@code 1} or {@code 0}
+     * @throws IndexOutOfBoundsException if the specified index is negative
+     */
+    int set(int bitIndex, boolean value) {
+        int wordIndex = wordIndex(bitIndex);
+        long bitMask = 1L << bitIndex;
+        int previous = (words[wordIndex] & bitMask) != 0 ? 1 : 0;
+        if (value) {
+            words[wordIndex] |= bitMask;
+        } else {
+            words[wordIndex] &= ~bitMask;
+        }
+        return previous;
+    }
+
+    int size() {
+        return size;
+    }
+}