Artificial intelligence and data

Particle swarm optimization

Particle swarm optimization (PSO) is a population-based metaheuristic algorithm introduced by James Kennedy and Russell Eberhart in 1995, inspired by the social behavior of bird flocks and fish schools.

Partition (database)

A partition in a database is one of the smaller physical pieces into which a large table is divided, stored and managed separately while remaining one logical table to queries.

Partition problem

The partition problem asks whether a multiset of positive integers can be divided into two subsets with equal sums. It is a classical NP-complete problem, proved by Karp in 1972.

PASCAL VOC

PASCAL VOC was a series of annual computer vision benchmark challenges run from 2005 to 2012, pairing annotated image datasets with standardized evaluation; its 20 object classes and detection metric remain in wide use.

Path tracing

Path tracing is a Monte Carlo rendering algorithm, introduced by James Kajiya in 1986, that traces random light paths from the camera to produce physically based, photorealistic images.

Path-planning algorithm

A path-planning algorithm computes a collision-free route for a robot or agent from a start to a goal position. Main approaches include graph search such as A, sampling-based planners such as RRT, and potential fields.

Pathfinding

Pathfinding is the computational problem of finding a route through a graph or map from a start to a goal, minimizing costs such as distance or travel time.

Pattern recognition

Pattern recognition, also called statistical pattern recognition, is the science of learning to distinguish patterns of interest from their background and classifying them, underpinning machine learning.

Paxos (computer science)

Paxos is a family of distributed consensus algorithms presented by Leslie Lamport in 1998, which keeps replicated systems safe despite crashes and lost messages and underlies Google's Chubby and Spanner.

PCP (complexity class)

PCP(r, q) is a complexity class of languages checkable by a probabilistic verifier using O(r) random bits and O(q) proof queries; the PCP theorem states NP equals PCP(O(log n), O(1)).

PCP (complexity)

PCP, or probabilistically checkable proof, is a proof format for NP statements that a randomized verifier can check by reading only a few positions of the proof.

PCP theorem

The PCP theorem is a result in computational complexity theory stating that NP equals PCP(log n, 1), so NP proofs can be verified by reading constant bits.

PDDL

PDDL, or Planning Domain Definition Language, is a standardized formal language for describing planning domains and problem instances to automated planners, created in 1998 for the AIPS-98 planning competition.

Peak detection (signal processing)

Peak detection is the computational identification of local maxima in measured signals, estimating each peak's position, height, width, and significance; it is standard in processing mass spectra and chromatograms.

Peak signal-to-noise ratio

Peak signal-to-noise ratio (PSNR) is a decibel metric that quantifies how faithfully a compressed or reconstructed image matches the original, widely used in image and video compression.

PEAQ

PEAQ (Perceptual Evaluation of Audio Quality), standardized as ITU-R BS.1387 in 1998, objectively measures perceived audio quality by comparing a processed signal against the original.

Penn Treebank

The Penn Treebank is an annotated corpus of over 4.5 million words of American English, tagged for part of speech and syntactic structure, built at the University of Pennsylvania.

Pentaho

Pentaho is a Java-based business-intelligence and data-integration software suite combining ETL, reporting, OLAP analysis, and data mining; founded in 2004, it has been owned by Hitachi Vantara since 2017.

Perceptron

The perceptron is a linear binary classifier described by Frank Rosenblatt in 1957, which learns by adjusting its weights only when it misclassifies a training example.

Perceptual hashing

A perceptual hash is a short fingerprint of an image, video, or audio file that stays similar under resizing, compression, and noise, enabling near-duplicate detection and media retrieval.

Perfect hash function

A perfect hash function, or perfect hashing, maps a fixed set of keys to distinct integers with no collisions, allowing lookup in a single probe.

Performer (transformer architecture)

The Performer is a 2020 transformer architecture from Google Research that approximates softmax attention with linear time and memory complexity via its FAVOR+ mechanism, and was presented at ICLR 2021.

Periodogram

The periodogram is a nonparametric estimator of a signal's power spectral density, computed from the squared magnitude of its Fourier transform; Arthur Schuster introduced it in 1898.

Permanent account number

The permanent account number (PAN) is a ten-character identifier issued by the Indian Income Tax Department, issued as a laminated PAN card or electronic e-PAN and valid for the holder's lifetime.

Permutation feature importance

Permutation feature importance, or permutation importance, is a model-agnostic machine learning technique, introduced by Leo Breiman in 2001, that measures feature importance by shuffling values and observing the drop in model performance.

Perplexity

Perplexity (PPL) is the standard evaluation metric for language models, measuring how surprised a model is by unseen text; introduced in 1977, it applies to autoregressive models.

Persistent data structure

A persistent data structure preserves every previous version of itself when updated, letting all versions be accessed; techniques include fat nodes, path copying, and structural sharing.

Persistent homology

Persistent homology is a topological data analysis method that tracks features like connected components, loops, and voids across scales, summarizing them as a barcode; long-lived features count as signal, short-lived ones as noise.

Person re-identification

Person re-identification (re-ID) is a computer vision task that assigns the same identity to a person seen in images or videos from different cameras, supporting multi-camera surveillance.