| /* |
| * 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. |
| */ |
| |
| /** |
| * The hllmap package contains a space efficient HLL mapping sketch of keys to approximate unique |
| * count of identifiers. For example, counting the number of unique users (identifiers) per IP |
| * address. |
| * |
| * <p>In cases where the number of keys is very large, having an individual HLL sketch per key may |
| * not be practical. If the distribution of values per key is highly skewed where the vast |
| * majority of keys have only a few values then this mapping sketch will make sense as it will be |
| * far more space efficient than dedicating individual HLL sketches per key. |
| * |
| * <p>From our own testing, sketching 100 million IPv4 addresses with such a |
| * highly skewed distribution of identifiers per IP uses only 1.4GB of memory. This translates to |
| * an average of about 10 bytes per IP allocated to the equivalent of a full k=1024 HLL sketch |
| * and provides an RSE of less than 2.5%. Your results will vary depending on the actual |
| * distribution of identifiers per key. |
| * |
| * @see org.apache.datasketches.hllmap.UniqueCountMap |
| * |
| * @author Lee Rhodes |
| * @author Kevin Lang |
| * @author Alexander Saydakov |
| */ |
| package org.apache.datasketches.hllmap; |
