| /* |
| * 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.hudi.common.bloom; |
| |
| /** |
| * Bloom filter utils. |
| */ |
| class BloomFilterUtils { |
| |
| /** |
| * Used in computing the optimal Bloom filter size. This approximately equals 0.480453. |
| */ |
| private static final double LOG2_SQUARED = Math.log(2) * Math.log(2); |
| |
| /** |
| * @return the bitsize given the total number of entries and error rate. |
| */ |
| static int getBitSize(int numEntries, double errorRate) { |
| return (int) Math.ceil(numEntries * (-Math.log(errorRate) / LOG2_SQUARED)); |
| } |
| |
| /** |
| * @return the number of hashes given the bitsize and total number of entries. |
| */ |
| static int getNumHashes(int bitSize, int numEntries) { |
| // Number of the hash functions |
| return (int) Math.ceil(Math.log(2) * bitSize / numEntries); |
| } |
| } |