| /* |
| * 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. |
| */ |
| |
| #ifndef _HLL_HPP_ |
| #define _HLL_HPP_ |
| |
| #include "common_defs.hpp" |
| #include "HllUtil.hpp" |
| |
| #include <memory> |
| #include <iostream> |
| #include <vector> |
| |
| namespace datasketches { |
| |
| /** |
| * This is a high performance implementation of Phillipe Flajolet’s HLL sketch but with |
| * significantly improved error behavior. If the ONLY use case for sketching is counting |
| * uniques and merging, the HLL sketch is a reasonable choice, although the highest performing in terms of accuracy for |
| * storage space consumed is CPC (Compressed Probabilistic Counting). For large enough counts, this HLL version (with HLL_4) can be 2 to |
| * 16 times smaller than the Theta sketch family for the same accuracy. |
| * |
| * <p>This implementation offers three different types of HLL sketch, each with different |
| * trade-offs with accuracy, space and performance. These types are specified with the |
| * {@link TgtHllType} parameter. |
| * |
| * <p>In terms of accuracy, all three types, for the same <i>lg_config_k</i>, have the same error |
| * distribution as a function of <i>n</i>, the number of unique values fed to the sketch. |
| * The configuration parameter <i>lg_config_k</i> is the log-base-2 of <i>K</i>, |
| * where <i>K</i> is the number of buckets or slots for the sketch. |
| * |
| * <p>During warmup, when the sketch has only received a small number of unique items |
| * (up to about 10% of <i>K</i>), this implementation leverages a new class of estimator |
| * algorithms with significantly better accuracy. |
| * |
| * <p>This sketch also offers the capability of operating off-heap. Given a WritableMemory object |
| * created by the user, the sketch will perform all of its updates and internal phase transitions |
| * in that object, which can actually reside either on-heap or off-heap based on how it is |
| * configured. In large systems that must update and merge many millions of sketches, having the |
| * sketch operate off-heap avoids the serialization and deserialization costs of moving sketches |
| * to and from off-heap memory-mapped files, for example, and eliminates big garbage collection |
| * delays. |
| * |
| * author Jon Malkin |
| * author Lee Rhodes |
| * author Kevin Lang |
| */ |
| |
| |
| /** |
| * Specifies the target type of HLL sketch to be created. It is a target in that the actual |
| * allocation of the HLL array is deferred until sufficient number of items have been received by |
| * the warm-up phases. |
| * |
| * <p>These three target types are isomorphic representations of the same underlying HLL algorithm. |
| * Thus, given the same value of <i>lg_config_k</i> and the same input, all three HLL target types |
| * will produce identical estimates and have identical error distributions.</p> |
| * |
| * <p>The memory (and also the serialization) of the sketch during this early warmup phase starts |
| * out very small (8 bytes, when empty) and then grows in increments of 4 bytes as required |
| * until the full HLL array is allocated. This transition point occurs at about 10% of K for |
| * sketches where lg_config_k is > 8.</p> |
| * |
| * <ul> |
| * <li><b>HLL_8</b> This uses an 8-bit byte per HLL bucket. It is generally the |
| * fastest in terms of update time, but has the largest storage footprint of about |
| * <i>K</i> bytes.</li> |
| * |
| * <li><b>HLL_6</b> This uses a 6-bit field per HLL bucket. It is the generally the next fastest |
| * in terms of update time with a storage footprint of about <i>3/4 * K</i> bytes.</li> |
| * |
| * <li><b>HLL_4</b> This uses a 4-bit field per HLL bucket and for large counts may require |
| * the use of a small internal auxiliary array for storing statistical exceptions, which are rare. |
| * For the values of <i>lg_config_k > 13</i> (<i>K</i> = 8192), |
| * this additional array adds about 3% to the overall storage. It is generally the slowest in |
| * terms of update time, but has the smallest storage footprint of about |
| * <i>K/2 * 1.03</i> bytes.</li> |
| * </ul> |
| */ |
| enum target_hll_type { |
| HLL_4, ///< 4 bits per entry (most compact, size may vary) |
| HLL_6, ///< 6 bits per entry (fixed size) |
| HLL_8 ///< 8 bits per entry (fastest, fixed size) |
| }; |
| |
| template<typename A> |
| class HllSketchImpl; |
| |
| template<typename A> |
| class hll_union_alloc; |
| |
| template<typename A> using AllocU8 = typename std::allocator_traits<A>::template rebind_alloc<uint8_t>; |
| template<typename A> using vector_u8 = std::vector<uint8_t, AllocU8<A>>; |
| |
| template<typename A = std::allocator<uint8_t> > |
| class hll_sketch_alloc final { |
| public: |
| /** |
| * Constructs a new HLL sketch. |
| * @param lg_config_k Sketch can hold 2^lg_config_k rows |
| * @param tgt_type The HLL mode to use, if/when the sketch reaches that state |
| * @param start_full_size Indicates whether to start in HLL mode, |
| * keeping memory use constant (if HLL_6 or HLL_8) at the cost of |
| * starting out using much more memory |
| */ |
| explicit hll_sketch_alloc(uint8_t lg_config_k, target_hll_type tgt_type = HLL_4, bool start_full_size = false, const A& allocator = A()); |
| |
| /** |
| * Copy constructor |
| */ |
| hll_sketch_alloc(const hll_sketch_alloc<A>& that); |
| |
| /** |
| * Copy constructor to a new target type |
| */ |
| hll_sketch_alloc(const hll_sketch_alloc<A>& that, target_hll_type tgt_type); |
| |
| /** |
| * Move constructor |
| */ |
| hll_sketch_alloc(hll_sketch_alloc<A>&& that) noexcept; |
| |
| /** |
| * Reconstructs a sketch from a serialized image on a stream. |
| * @param is An input stream with a binary image of a sketch |
| */ |
| static hll_sketch_alloc deserialize(std::istream& is, const A& allocator = A()); |
| |
| /** |
| * Reconstructs a sketch from a serialized image in a byte array. |
| * @param is bytes An input array with a binary image of a sketch |
| * @param len Length of the input array, in bytes |
| */ |
| static hll_sketch_alloc deserialize(const void* bytes, size_t len, const A& allocator = A()); |
| |
| //! Class destructor |
| virtual ~hll_sketch_alloc(); |
| |
| //! Copy assignment operator |
| hll_sketch_alloc operator=(const hll_sketch_alloc<A>& other); |
| |
| //! Move assignment operator |
| hll_sketch_alloc operator=(hll_sketch_alloc<A>&& other); |
| |
| /** |
| * Resets the sketch to an empty state in coupon collection mode. |
| * Does not re-use existing internal objects. |
| */ |
| void reset(); |
| |
| typedef vector_u8<A> vector_bytes; // alias for users |
| |
| /** |
| * Serializes the sketch to a byte array, compacting data structures |
| * where feasible to eliminate unused storage in the serialized image. |
| * @param header_size_bytes Allows for PostgreSQL integration |
| */ |
| vector_bytes serialize_compact(unsigned header_size_bytes = 0) const; |
| |
| /** |
| * Serializes the sketch to a byte array, retaining all internal |
| * data structures in their current form. |
| */ |
| vector_bytes serialize_updatable() const; |
| |
| /** |
| * Serializes the sketch to an ostream, compacting data structures |
| * where feasible to eliminate unused storage in the serialized image. |
| * @param os std::ostream to use for output. |
| */ |
| void serialize_compact(std::ostream& os) const; |
| |
| /** |
| * Serializes the sketch to an ostream, retaining all internal data |
| * structures in their current form. |
| * @param os std::ostream to use for output. |
| */ |
| void serialize_updatable(std::ostream& os) const; |
| |
| /** |
| * Human readable summary with optional detail |
| * @param summary if true, output the sketch summary |
| * @param detail if true, output the internal data array |
| * @param auxDetail if true, output the internal Aux array, if it exists. |
| * @param all if true, outputs all entries including empty ones |
| * @return human readable string with optional detail. |
| */ |
| string<A> to_string(bool summary = true, |
| bool detail = false, |
| bool aux_detail = false, |
| bool all = false) const; |
| |
| /** |
| * Present the given std::string as a potential unique item. |
| * The string is converted to a byte array using UTF8 encoding. |
| * If the string is null or empty no update attempt is made and the method returns. |
| * @param datum The given string. |
| */ |
| void update(const std::string& datum); |
| |
| /** |
| * Present the given unsigned 64-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint64_t datum); |
| |
| /** |
| * Present the given unsigned 32-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint32_t datum); |
| |
| /** |
| * Present the given unsigned 16-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint16_t datum); |
| |
| /** |
| * Present the given unsigned 8-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint8_t datum); |
| |
| /** |
| * Present the given signed 64-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int64_t datum); |
| |
| /** |
| * Present the given signed 32-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int32_t datum); |
| |
| /** |
| * Present the given signed 16-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int16_t datum); |
| |
| /** |
| * Present the given signed 8-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int8_t datum); |
| |
| /** |
| * Present the given 64-bit floating point value as a potential unique item. |
| * @param datum The given double. |
| */ |
| void update(double datum); |
| |
| /** |
| * Present the given 32-bit floating point value as a potential unique item. |
| * @param datum The given float. |
| */ |
| void update(float datum); |
| |
| /** |
| * Present the given data array as a potential unique item. |
| * @param data The given array. |
| * @param length_bytes The array length in bytes. |
| */ |
| void update(const void* data, size_t length_bytes); |
| |
| /** |
| * Returns the current cardinality estimate |
| * @return the cardinality estimate |
| */ |
| double get_estimate() const; |
| |
| /** |
| * This is less accurate than the getEstimate() method |
| * and is automatically used when the sketch has gone through |
| * union operations where the more accurate HIP estimator cannot |
| * be used. |
| * |
| * This is made public only for error characterization software |
| * that exists in separate packages and is not intended for normal |
| * use. |
| * @return the composite cardinality estimate |
| */ |
| double get_composite_estimate() const; |
| |
| /** |
| * Returns the approximate lower error bound given the specified |
| * number of standard deviations. |
| * @param num_std_dev Number of standard deviations, an integer from the set {1, 2, 3}. |
| * @return The approximate lower bound. |
| */ |
| double get_lower_bound(uint8_t num_std_dev) const; |
| |
| /** |
| * Returns the approximate upper error bound given the specified |
| * number of standard deviations. |
| * @param num_std_dev Number of standard deviations, an integer from the set {1, 2, 3}. |
| * @return The approximate upper bound. |
| */ |
| double get_upper_bound(uint8_t num_std_dev) const; |
| |
| /** |
| * Returns sketch's configured lg_k value. |
| * @return Configured lg_k value. |
| */ |
| uint8_t get_lg_config_k() const; |
| |
| /** |
| * Returns the sketch's target HLL mode (from #target_hll_type). |
| * @return The sketch's target HLL mode. |
| */ |
| target_hll_type get_target_type() const; |
| |
| /** |
| * Indicates if the sketch is currently stored compacted. |
| * @return True if the sketch is stored in compact form. |
| */ |
| bool is_compact() const; |
| |
| /** |
| * Indicates if the sketch is currently empty. |
| * @return True if the sketch is empty. |
| */ |
| bool is_empty() const; |
| |
| /** |
| * Returns the size of the sketch serialized in compact form. |
| * @return Size of the sketch serialized in compact form, in bytes. |
| */ |
| uint32_t get_compact_serialization_bytes() const; |
| |
| /** |
| * Returns the size of the sketch serialized without compaction. |
| * @return Size of the sketch serialized without compaction, in bytes. |
| */ |
| uint32_t get_updatable_serialization_bytes() const; |
| |
| /** |
| * Returns the maximum size in bytes that this sketch can grow to |
| * given lg_config_k. However, for the HLL_4 sketch type, this |
| * value can be exceeded in extremely rare cases. If exceeded, it |
| * will be larger by only a few percent. |
| * |
| * @param lg_config_k The Log2 of K for the target HLL sketch. This value must be |
| * between 4 and 21 inclusively. |
| * @param tgt_type the desired Hll type |
| * @return the maximum size in bytes that this sketch can grow to. |
| */ |
| static uint32_t get_max_updatable_serialization_bytes(uint8_t lg_k, target_hll_type tgt_type); |
| |
| /** |
| * Gets the current (approximate) Relative Error (RE) asymptotic values given several |
| * parameters. This is used primarily for testing. |
| * @param upper_bound return the RE for the Upper Bound, otherwise for the Lower Bound. |
| * @param unioned set true if the sketch is the result of a union operation. |
| * @param lg_config_k the configured value for the sketch. |
| * @param num_std_dev the given number of Standard Deviations. This must be an integer between |
| * 1 and 3, inclusive. |
| * @return the current (approximate) RelativeError |
| */ |
| static double get_rel_err(bool upper_bound, bool unioned, |
| uint8_t lg_config_k, uint8_t num_std_dev); |
| |
| private: |
| explicit hll_sketch_alloc(HllSketchImpl<A>* that); |
| |
| void coupon_update(uint32_t coupon); |
| |
| std::string type_as_string() const; |
| std::string mode_as_string() const; |
| |
| hll_mode get_current_mode() const; |
| uint8_t get_serialization_version() const; |
| bool is_out_of_order_flag() const; |
| bool is_estimation_mode() const; |
| |
| typedef typename std::allocator_traits<A>::template rebind_alloc<hll_sketch_alloc> AllocHllSketch; |
| |
| HllSketchImpl<A>* sketch_impl; |
| friend hll_union_alloc<A>; |
| }; |
| |
| /** |
| * This performs union operations for HLL sketches. This union operator is configured with a |
| * <i>lgMaxK</i> instead of the normal <i>lg_config_k</i>. |
| * |
| * <p>This union operator does permit the unioning of sketches with different values of |
| * <i>lg_config_k</i>. The user should be aware that the resulting accuracy of a sketch returned |
| * at the end of the unioning process will be a function of the smallest of <i>lg_max_k</i> and |
| * <i>lg_config_k</i> that the union operator has seen. |
| * |
| * <p>This union operator also permits unioning of any of the three different target hll_sketch |
| * types. |
| * |
| * <p>Although the API for this union operator parallels many of the methods of the |
| * <i>HllSketch</i>, the behavior of the union operator has some fundamental differences. |
| * |
| * <p>First, the user cannot specify the #tgt_hll_type as an input parameter. |
| * Instead, it is specified for the sketch returned with #get_result(tgt_hll_tyope). |
| * |
| * <p>Second, the internal effective value of log-base-2 of <i>k</i> for the union operation can |
| * change dynamically based on the smallest <i>lg_config_k</i> that the union operation has seen. |
| * |
| * author Jon Malkin |
| * author Lee Rhodes |
| * author Kevin Lang |
| */ |
| |
| template<typename A = std::allocator<uint8_t> > |
| class hll_union_alloc { |
| public: |
| /** |
| * Construct an hll_union operator with the given maximum log2 of k. |
| * @param lg_max_k The maximum size, in log2, of k. The value must |
| * be between 7 and 21, inclusive. |
| */ |
| explicit hll_union_alloc(uint8_t lg_max_k, const A& allocator = A()); |
| |
| /** |
| * Returns the current cardinality estimate |
| * @return the cardinality estimate |
| */ |
| double get_estimate() const; |
| |
| /** |
| * This is less accurate than the get_estimate() method |
| * and is automatically used when the union has gone through |
| * union operations where the more accurate HIP estimator cannot |
| * be used. |
| * |
| * This is made public only for error characterization software |
| * that exists in separate packages and is not intended for normal |
| * use. |
| * @return the composite cardinality estimate |
| */ |
| double get_composite_estimate() const; |
| |
| /** |
| * Returns the approximate lower error bound given the specified |
| * number of standard deviations. |
| * @param num_std_dev Number of standard deviations, an integer from the set {1, 2, 3}. |
| * @return The approximate lower bound. |
| */ |
| double get_lower_bound(uint8_t num_std_dev) const; |
| |
| /** |
| * Returns the approximate upper error bound given the specified |
| * number of standard deviations. |
| * @param num_std_dev Number of standard deviations, an integer from the set {1, 2, 3}. |
| * @return The approximate upper bound. |
| */ |
| double get_upper_bound(uint8_t num_std_dev) const; |
| |
| /** |
| * Returns union's configured lg_k value. |
| * @return Configured lg_k value. |
| */ |
| uint8_t get_lg_config_k() const; |
| |
| /** |
| * Returns the union's target HLL mode (from #target_hll_type). |
| * @return The union's target HLL mode. |
| */ |
| target_hll_type get_target_type() const; |
| |
| /** |
| * Indicates if the union is currently empty. |
| * @return True if the union is empty. |
| */ |
| bool is_empty() const; |
| |
| /** |
| * Resets the union to an empty state in coupon collection mode. |
| * Does not re-use existing internal objects. |
| */ |
| void reset(); |
| |
| /** |
| * Returns the result of this union operator with the specified |
| * #tgt_hll_type. |
| * @param The tgt_hll_type enum value of the desired result (Default: HLL_4) |
| * @return The result of this union with the specified tgt_hll_type |
| */ |
| hll_sketch_alloc<A> get_result(target_hll_type tgt_type = HLL_4) const; |
| |
| /** |
| * Update this union operator with the given sketch. |
| * @param The given sketch. |
| */ |
| void update(const hll_sketch_alloc<A>& sketch); |
| |
| /** |
| * Update this union operator with the given temporary sketch. |
| * @param The given sketch. |
| */ |
| void update(hll_sketch_alloc<A>&& sketch); |
| |
| /** |
| * Present the given std::string as a potential unique item. |
| * The string is converted to a byte array using UTF8 encoding. |
| * If the string is null or empty no update attempt is made and the method returns. |
| * @param datum The given string. |
| */ |
| void update(const std::string& datum); |
| |
| /** |
| * Present the given unsigned 64-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint64_t datum); |
| |
| /** |
| * Present the given unsigned 32-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint32_t datum); |
| |
| /** |
| * Present the given unsigned 16-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint16_t datum); |
| |
| /** |
| * Present the given unsigned 8-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(uint8_t datum); |
| |
| /** |
| * Present the given signed 64-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int64_t datum); |
| |
| /** |
| * Present the given signed 32-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int32_t datum); |
| |
| /** |
| * Present the given signed 16-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int16_t datum); |
| |
| /** |
| * Present the given signed 8-bit integer as a potential unique item. |
| * @param datum The given integer. |
| */ |
| void update(int8_t datum); |
| |
| /** |
| * Present the given 64-bit floating point value as a potential unique item. |
| * @param datum The given double. |
| */ |
| void update(double datum); |
| |
| /** |
| * Present the given 32-bit floating point value as a potential unique item. |
| * @param datum The given float. |
| */ |
| void update(float datum); |
| |
| /** |
| * Present the given data array as a potential unique item. |
| * @param data The given array. |
| * @param length_bytes The array length in bytes. |
| */ |
| void update(const void* data, size_t length_bytes); |
| |
| /** |
| * Gets the current (approximate) Relative Error (RE) asymptotic values given several |
| * parameters. This is used primarily for testing. |
| * @param upper_bound return the RE for the Upper Bound, otherwise for the Lower Bound. |
| * @param unioned set true if the sketch is the result of a union operation. |
| * @param lg_config_k the configured value for the sketch. |
| * @param num_std_dev the given number of Standard Deviations. This must be an integer between |
| * 1 and 3, inclusive. |
| * @return the current (approximate) RelativeError |
| */ |
| static double get_rel_err(bool upper_bound, bool unioned, |
| uint8_t lg_config_k, uint8_t num_std_dev); |
| |
| private: |
| |
| /** |
| * Union the given source and destination sketches. This method examines the state of |
| * the current internal gadget and the incoming sketch and determines the optimal way to |
| * perform the union. This may involve swapping, down-sampling, transforming, and / or |
| * copying one of the arguments and may completely replace the internals of the union. |
| * |
| * @param incoming_impl the given incoming sketch, which may not be modified. |
| * @param lg_max_k the maximum value of log2 K for this union. |
| */ |
| inline void union_impl(const hll_sketch_alloc<A>& sketch, uint8_t lg_max_k); |
| |
| static HllSketchImpl<A>* copy_or_downsample(const HllSketchImpl<A>* src_impl, uint8_t tgt_lg_k); |
| |
| void coupon_update(uint32_t coupon); |
| |
| hll_mode get_current_mode() const; |
| bool is_out_of_order_flag() const; |
| bool is_estimation_mode() const; |
| |
| // calls couponUpdate on sketch, freeing the old sketch upon changes in hll_mode |
| static HllSketchImpl<A>* leak_free_coupon_update(HllSketchImpl<A>* impl, uint32_t coupon); |
| |
| uint8_t lg_max_k_; |
| hll_sketch_alloc<A> gadget_; |
| }; |
| |
| /// convenience alias for hll_sketch with default allocator |
| typedef hll_sketch_alloc<> hll_sketch; |
| |
| /// convenience alias for hll_union with default allocator |
| typedef hll_union_alloc<> hll_union; |
| |
| } // namespace datasketches |
| |
| #include "hll.private.hpp" |
| |
| #endif // _HLL_HPP_ |
