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| <li class="toctree-l3"><a class="reference internal" href="#datasketches.ebpps_sketch"><code class="docutils literal notranslate"><span class="pre">ebpps_sketch</span></code></a><ul> |
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| <section id="exact-and-bounded-probabilitiy-proportional-to-size-ebpps-sampling"> |
| <h1>Exact and Bounded, Probabilitiy Proportional to Size (EBPPS) Sampling<a class="headerlink" href="#exact-and-bounded-probabilitiy-proportional-to-size-ebpps-sampling" title="Link to this heading"></a></h1> |
| <p>An EBPPS sketch produces a randome sample of data from a stream of items, ensuring that the probability |
| of including an item is always exactly equal to the item’s size. The size of an item is defined as its |
| weight relative to the total weight of all items seen so far by the sketch. In contrast to VarOpt sampling, |
| this sketch may return fewer than <cite>k</cite> items in order to keep the probability of including an item strictly |
| proportional to its size.</p> |
| <p>This sketch is based on: B. Hentschel, P. J. Haas, Y. Tian |
| “Exact PPS Sampling with Bounded Sample Size”, |
| Information Processing Letters, 2023.</p> |
| <p>EBPPS sampling is related to reservoir sampling, but handles unequal item weights. |
| Feeding the sketch items with a uniform weight value will produce a sample equivalent to reservoir sampling.</p> |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>Serializing and deserializing this sketch requires the use of a <a class="reference internal" href="../helper/serde.html#datasketches.PyObjectSerDe" title="datasketches.PyObjectSerDe"><code class="xref py py-class docutils literal notranslate"><span class="pre">PyObjectSerDe</span></code></a>.</p> |
| </div> |
| <dl class="py class"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch"> |
| <em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">ebpps_sketch</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#datasketches.ebpps_sketch" title="Link to this definition"></a></dt> |
| <dd><p class="rubric">Static Methods:</p> |
| <dl class="py method"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.deserialize"> |
| <span class="sig-name descname"><span class="pre">deserialize</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">bytes</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">bytes</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">serde</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><a class="reference internal" href="../helper/serde.html#datasketches.PyObjectSerDe" title="_datasketches.PyObjectSerDe"><span class="pre">_datasketches.PyObjectSerDe</span></a></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><a class="reference internal" href="#datasketches.ebpps_sketch" title="_datasketches.ebpps_sketch"><span class="pre">_datasketches.ebpps_sketch</span></a></span></span><a class="headerlink" href="#datasketches.ebpps_sketch.deserialize" title="Link to this definition"></a></dt> |
| <dd><p>Reads a bytes object and returns the corresponding ebpps_sketch</p> |
| </dd></dl> |
| |
| <p class="rubric">Non-static Methods:</p> |
| <dl class="py method"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.__init__"> |
| <span class="sig-name descname"><span class="pre">__init__</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">self</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">k</span></span><span class="p"><span class="pre">:</span></span><span class="w"> </span><span class="n"><span class="pre">int</span></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><span class="pre">None</span></span></span><a class="headerlink" href="#datasketches.ebpps_sketch.__init__" title="Link to this definition"></a></dt> |
| <dd><p>Creates a new EBPPS sketch instance</p> |
| <dl class="field-list simple"> |
| <dt class="field-odd">Parameters<span class="colon">:</span></dt> |
| <dd class="field-odd"><p><strong>k</strong> (<em>int</em>) – Maximum number of samples in the sketch</p> |
| </dd> |
| </dl> |
| </dd></dl> |
| |
| <dl class="py property"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.c"> |
| <em class="property"><span class="k"><span class="pre">property</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">c</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.c" title="Link to this definition"></a></dt> |
| <dd><p>The expected number of samples returned upon a call to get_result() or the creation of an iterator. The number is a floating point value, where the fractional portion represents the probability of including a “partial item” from the sample. The value C should be no larger than the sketch’s configured value of k, although numerical precision limitations mean it may exceed k by double precision floating point error margins in certain cases.</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.get_serialized_size_bytes"> |
| <span class="sig-name descname"><span class="pre">get_serialized_size_bytes</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.get_serialized_size_bytes" title="Link to this definition"></a></dt> |
| <dd><p>Computes the size in bytes needed to serialize the current sketch</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.is_empty"> |
| <span class="sig-name descname"><span class="pre">is_empty</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.is_empty" title="Link to this definition"></a></dt> |
| <dd><p>Returns True if the sketch is empty, otherwise False</p> |
| </dd></dl> |
| |
| <dl class="py property"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.k"> |
| <em class="property"><span class="k"><span class="pre">property</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">k</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.k" title="Link to this definition"></a></dt> |
| <dd><p>The sketch’s maximum configured sample size</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.merge"> |
| <span class="sig-name descname"><span class="pre">merge</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.merge" title="Link to this definition"></a></dt> |
| <dd><p>Merges the sketch with the given sketch</p> |
| </dd></dl> |
| |
| <dl class="py property"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.n"> |
| <em class="property"><span class="k"><span class="pre">property</span></span><span class="w"> </span></em><span class="sig-name descname"><span class="pre">n</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.n" title="Link to this definition"></a></dt> |
| <dd><p>The total stream length</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.serialize"> |
| <span class="sig-name descname"><span class="pre">serialize</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.serialize" title="Link to this definition"></a></dt> |
| <dd><p>Serializes the sketch into a bytes object</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.to_string"> |
| <span class="sig-name descname"><span class="pre">to_string</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.to_string" title="Link to this definition"></a></dt> |
| <dd><p>Produces a string summary of the sketch and optionally prints the items</p> |
| </dd></dl> |
| |
| <dl class="py attribute"> |
| <dt class="sig sig-object py" id="datasketches.ebpps_sketch.update"> |
| <span class="sig-name descname"><span class="pre">update</span></span><a class="headerlink" href="#datasketches.ebpps_sketch.update" title="Link to this definition"></a></dt> |
| <dd><p>Updates the sketch with the given value and weight</p> |
| </dd></dl> |
| |
| </dd></dl> |
| |
| </section> |
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