Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/10883#discussion_r50630113
--- Diff:
common/sketch/src/main/java/org/apache/spark/util/sketch/DefaultBloomFilter.java
---
@@ -0,0 +1,220 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.spark.util.sketch;
+
+import java.io.UnsupportedEncodingException;
+import java.util.Arrays;
+
+public class DefaultBloomFilter extends BloomFilter {
+
+ private final int numHashFunctions;
+ private final BitArray bits;
+
+ public DefaultBloomFilter(int numHashFunctions, long numBits) {
+ this.numHashFunctions = numHashFunctions;
+ this.bits = new BitArray(numBits);
+ }
+
+ @Override
+ public double expectedFpp() {
+ return Math.pow((double) bits.bitCount() / bits.bitSize(),
numHashFunctions);
+ }
+
+ @Override
+ public long bitSize() {
+ return bits.bitSize();
+ }
+
+ private static long hashObjectToLong(Object item) {
+ if (item instanceof String) {
+ try {
+ byte[] bytes = ((String) item).getBytes("utf-8");
+ return hashBytesToLong(bytes);
+ } catch (UnsupportedEncodingException e) {
+ throw new RuntimeException("Only support utf-8 string", e);
+ }
+ } else {
+ long longValue;
+
+ if (item instanceof Long) {
+ longValue = (Long) item;
+ } else if (item instanceof Integer) {
+ longValue = ((Integer) item).longValue();
+ } else if (item instanceof Short) {
+ longValue = ((Short) item).longValue();
+ } else if (item instanceof Byte) {
+ longValue = ((Byte) item).longValue();
+ } else {
+ throw new IllegalArgumentException(
+ "Support for " + item.getClass().getName() + " not implemented"
+ );
+ }
+
+ int h1 = Murmur3_x86_32.hashLong(longValue, 0);
+ int h2 = Murmur3_x86_32.hashLong(longValue, h1);
+ return (((long) h1) << 32) | (h2 & 0xFFFFFFFFL);
+ }
+ }
+
+ private static long hashBytesToLong(byte[] bytes) {
+ int h1 = Murmur3_x86_32.hashUnsafeBytes(bytes,
Platform.BYTE_ARRAY_OFFSET, bytes.length, 0);
+ int h2 = Murmur3_x86_32.hashUnsafeBytes(bytes,
Platform.BYTE_ARRAY_OFFSET, bytes.length, h1);
+ return (((long) h1) << 32) | (h2 & 0xFFFFFFFFL);
+ }
+
+ @Override
+ public boolean put(Object item) {
+ long bitSize = bits.bitSize();
+ long hash64 = hashObjectToLong(item);
+ int h1 = (int) (hash64 >> 32);
+ int h2 = (int) hash64;
+
+ boolean bitsChanged = false;
+ for (int i = 1; i <= numHashFunctions; i++) {
+ int combinedHash = h1 + (i * h2);
+ // Flip all the bits if it's negative (guaranteed positive number)
+ if (combinedHash < 0) {
+ combinedHash = ~combinedHash;
+ }
+ bitsChanged |= bits.set(combinedHash % bitSize);
+ }
+ return bitsChanged;
+ }
+
+ @Override
+ public boolean mightContain(Object item) {
+ long bitSize = bits.bitSize();
+ long hash64 = hashObjectToLong(item);
+ int h1 = (int) (hash64 >> 32);
+ int h2 = (int) hash64;
+
+ for (int i = 1; i <= numHashFunctions; i++) {
+ int combinedHash = h1 + (i * h2);
+ // Flip all the bits if it's negative (guaranteed positive number)
+ if (combinedHash < 0) {
+ combinedHash = ~combinedHash;
+ }
+ if (!bits.get(combinedHash % bitSize)) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ @Override
+ public boolean isCompatible(BloomFilter other) {
+ if (other == null) {
+ return false;
+ }
+
+ if (!(other instanceof DefaultBloomFilter)) {
+ return false;
+ }
+
+ DefaultBloomFilter that = (DefaultBloomFilter) other;
+ return this.bitSize() == that.bitSize() && this.numHashFunctions ==
that.numHashFunctions;
+ }
+
+ @Override
+ public BloomFilter mergeInPlace(BloomFilter other) {
+ if (!isCompatible(other)) {
+ throw new IllegalArgumentException("Can't merge incompatible bloom
filter");
+ }
+
+ DefaultBloomFilter that = (DefaultBloomFilter) other;
+ this.bits.putAll(that.bits);
+ return this;
+ }
+
+ static final class BitArray {
--- End diff --
I'd move this out of this file and just have a BitSet class. We should have
a test suite for this too.
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