hll

HLL is an acronym used in several contexts in computing and data processing. It may refer to high-level languages or to HyperLogLog, a probabilistic data structure for cardinality estimation, among other uses.

As a general term, high-level language (HLL) denotes a programming language designed to be easy for humans to read and write, abstracting most hardware details. Such languages enable platform independence, automatic memory management, and rich abstractions. They contrast with low-level languages that provide finer control over hardware.

HyperLogLog is a compact algorithm for estimating the number of distinct elements in a data set. It uses hash functions and a small number of registers to produce an approximate count with a controlled error that scales with the size of the register array. The standard error is approximately 1.04 divided by the square root of m, where m is the number of registers (often a power of two). HyperLogLog is widely used in database systems, analytics pipelines, and streaming platforms to track cardinalities in large-scale data without storing all elements. Variants such as HyperLogLog++ improve accuracy and implementational details.

In practice, the meaning of HLL depends on the context, and articles or software naming conventions should specify which interpretation is intended.