https://yy-tech.online/tags/cache/ Recent content in Cache on H&W Hugo en Thu, 28 May 2026 00:53:02 +0800 https://yy-tech.online/post/play-with-bloomfilter/ Fri, 07 Aug 2020 11:38:41 +0800 https://yy-tech.online/post/play-with-bloomfilter/ <h2 id="what-is-a-bloom-filter">What Is a Bloom Filter?</h2> <p>A Bloom filter is a space-efficient probabilistic data structure used to test whether an element is a member of a set. When an element is added, it is hashed by <strong>K independent hash functions</strong>, each mapping the element to a position in a bit array, which is then set to <code>1</code>.</p> <p>To query membership, the same K positions are checked:</p> <ul> <li>If <strong>any bit is 0</strong> → the element is <strong>definitely not</strong> in the set.</li> <li>If <strong>all bits are 1</strong> → the element is <strong>probably</strong> in the set (false positives are possible).</li> </ul> <p>The key difference from a single-hash bitmap: using K hash functions spreads the load and significantly reduces collision probability.</p>