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Core sketch algorithms used alone and by other Java repositories in the DataSketches library.
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/*
 * 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.datasketches.quantilescommon;

import static org.apache.datasketches.quantilescommon.QuantileSearchCriteria.INCLUSIVE;

/**
 * This enables the special functions for performing efficient partitioning of massive data.
 */
public interface PartitioningFeature {

  /**
   * This method returns an instance of
   * {@link GenericPartitionBoundaries GenericPartitionBoundaries} which provides
   * sufficient information for the user to create the given number of equally sized partitions, where "equally sized"
   * refers to an approximately equal number of items per partition.
   *
   * This method is equivalent to
   * {@link #getPartitionBoundaries(int, QuantileSearchCriteria) getPartitionBoundaries(numEquallySized, INCLUSIVE)}.
   * 
   *
   * @param numEquallySized an integer that specifies the number of equally sized partitions between
   * {@link GenericPartitionBoundaries#getMinItem() getMinItem()} and
   * {@link GenericPartitionBoundaries#getMaxItem() getMaxItem()}.
   * This must be a positive integer greater than zero.
   * 
   * A 1 will return: minItem, maxItem.
   * A 2 will return: minItem, median quantile, maxItem.
   * Etc.
   * 
   *
   * @return an instance of {@link GenericPartitionBoundaries GenericPartitionBoundaries}.
   * @throws IllegalArgumentException if sketch is empty.
   * @throws IllegalArgumentException if numEquallySized is less than 1.
   */
  default GenericPartitionBoundaries getPartitionBoundaries(int numEquallySized) {
    return getPartitionBoundaries(numEquallySized, INCLUSIVE);
  }

  /**
   * This method returns an instance of
   * {@link GenericPartitionBoundaries GenericPartitionBoundaries} which provides
   * sufficient information for the user to create the given number of equally sized partitions, where "equally sized"
   * refers to an approximately equal number of items per partition.
   *
   * @param numEquallySized an integer that specifies the number of equally sized partitions between
   * {@link GenericPartitionBoundaries#getMinItem() getMinItem()} and
   * {@link GenericPartitionBoundaries#getMaxItem() getMaxItem()}.
   * This must be a positive integer greater than zero.
   * 
   * A 1 will return: minItem, maxItem.
   * A 2 will return: minItem, median quantile, maxItem.
   * Etc.
   * 
   *
   * @param searchCrit
   * If INCLUSIVE, all the returned quantiles are the upper boundaries of the equally sized partitions
   * with the exception of the lowest returned quantile, which is the lowest boundary of the lowest ranked partition.
   * If EXCLUSIVE, all the returned quantiles are the lower boundaries of the equally sized partitions
   * with the exception of the highest returned quantile, which is the upper boundary of the highest ranked partition.
   *
   * @return an instance of {@link GenericPartitionBoundaries GenericPartitionBoundaries}.
   * @throws IllegalArgumentException if sketch is empty.
   * @throws IllegalArgumentException if numEquallySized is less than 1.
   */
  GenericPartitionBoundaries getPartitionBoundaries(int numEquallySized, QuantileSearchCriteria searchCrit);

}