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Embarrassingly parallel
View on WikipediaIn parallel computing, an embarrassingly parallel workload or problem (also called embarrassingly parallelizable, perfectly parallel, delightfully parallel or pleasingly parallel) is one where little or no effort is needed to split the problem into a number of parallel tasks.[1] This is due to minimal or no dependency upon communication between the parallel tasks, or for results between them.[2]
These differ from distributed computing problems, which need communication between tasks, especially communication of intermediate results. They are easier to perform on server farms which lack the special infrastructure used in a true supercomputer cluster. They are well-suited to large, Internet-based volunteer computing platforms such as BOINC, and suffer less from parallel slowdown. The opposite of embarrassingly parallel problems are inherently serial problems, which cannot be parallelized at all.
A common example of an embarrassingly parallel problem is 3D video rendering handled by a graphics processing unit, where each frame (forward method) or pixel (ray tracing method) can be handled with no interdependency.[3] Some forms of password cracking are another embarrassingly parallel task that is easily distributed on central processing units, CPU cores, or clusters.
Etymology
[edit]"Embarrassingly" is used here to refer to parallelization problems which are "embarrassingly easy".[4] The term may imply embarrassment on the part of developers or compilers: "Because so many important problems remain unsolved mainly due to their intrinsic computational complexity, it would be embarrassing not to develop parallel implementations of polynomial homotopy continuation methods."[5] The term is first found in the literature in a 1986 book on multiprocessors by MATLAB's creator Cleve Moler,[6] who claims to have invented the term.[7]
An alternative term, pleasingly parallel, has gained some use, perhaps to avoid the negative connotations of embarrassment in favor of a positive reflection on the parallelizability of the problems: "Of course, there is nothing embarrassing about these programs at all."[8]
Examples
[edit]A trivial example involves serving static data. It would take very little effort to have many processing units produce the same set of bits. Indeed, the famous Hello World problem could easily be parallelized with few programming considerations or computational costs.
Some examples of embarrassingly parallel problems include:
- Monte Carlo method[9]
- Distributed relational database queries using distributed set processing.
- Numerical integration[10]
- Bulk processing of unrelated files of similar nature in general, such as photo gallery resizing and conversion.
- The Mandelbrot set, Perlin noise and similar images, where each point is calculated independently.
- Rendering of computer graphics. In computer animation, each frame or pixel may be rendered independently .
- Some brute-force searches in cryptography.[11] Notable real-world examples include distributed.net and proof-of-work systems used in cryptocurrency.
- BLAST searches in bioinformatics with split databases.[12]
- Large scale facial recognition systems that compare thousands of arbitrary acquired faces (e.g., a security or surveillance video via closed-circuit television) with similarly large number of previously stored faces (e.g., a rogues gallery or similar watch list).[13]
- Computer simulations comparing many independent scenarios.
- Genetic algorithms.[14]
- Ensemble calculations of numerical weather prediction.
- Event simulation and reconstruction in particle physics.
- The marching squares algorithm.
- Sieving step of the quadratic sieve and the number field sieve.
- Tree growth step of the random forest machine learning technique.
- Discrete Fourier transform where each harmonic is independently calculated.
- Convolutional neural networks running on GPUs.
- Parallel search in constraint programming[15]
Implementations
[edit]- In R (programming language) – The Simple Network of Workstations (SNOW) package implements a simple mechanism for using a set of workstations or a Beowulf cluster for embarrassingly parallel computations.[16] Similar R packages include "future", "parallel" and others.
See also
[edit]- Amdahl's law defines value P, which would be almost or exactly equal to 1 for embarrassingly parallel problems.
- Cellular automaton
- Connection Machine
- CUDA framework
- Manycore processor
- Map (parallel pattern)
- Massively parallel
- Multiprocessing
- Parallel computing
- Process-oriented programming
- Shared-nothing architecture (SN)
- Symmetric multiprocessing (SMP)
- Vector processor
References
[edit]- ^ Herlihy, Maurice; Shavit, Nir (2012). The Art of Multiprocessor Programming, Revised Reprint (revised ed.). Elsevier. p. 14. ISBN 9780123977953. Retrieved 28 February 2016.
Some computational problems are "embarrassingly parallel": they can easily be divided into components that can be executed concurrently.
- ^ Section 1.4.4 of: Foster, Ian (1995). Designing and Building Parallel Programs. Addison–Wesley. ISBN 9780201575941. Archived from the original on 2011-03-01.
- ^ Alan Chalmers; Erik Reinhard; Tim Davis (21 March 2011). Practical Parallel Rendering. CRC Press. ISBN 978-1-4398-6380-0.
- ^ Matloff, Norman (2011). The Art of R Programming: A Tour of Statistical Software Design, p.347. No Starch. ISBN 9781593274108.
- ^ Leykin, Anton; Verschelde, Jan; Zhuang, Yan (2006). "Parallel Homotopy Algorithms to Solve Polynomial Systems". Mathematical Software - ICMS 2006. Lecture Notes in Computer Science. Vol. 4151. pp. 225–234. doi:10.1007/11832225_22. ISBN 978-3-540-38084-9.
- ^ Moler, Cleve (1986). "Matrix Computation on Distributed Memory Multiprocessors". In Heath, Michael T. (ed.). Hypercube Multiprocessors. Society for Industrial and Applied Mathematics, Philadelphia. ISBN 978-0898712094.
- ^ The Intel hypercube part 2 reposted on Cleve's Corner blog on The MathWorks website
- ^ Kepner, Jeremy (2009). Parallel MATLAB for Multicore and Multinode Computers, p.12. SIAM. ISBN 9780898716733.
- ^ Erricos John Kontoghiorghes (21 December 2005). Handbook of Parallel Computing and Statistics. CRC Press. ISBN 978-1-4200-2868-3.
- ^ Yuefan Deng (2013). Applied Parallel Computing. World Scientific. ISBN 978-981-4307-60-4.
- ^ Josefsson, Simon; Percival, Colin (August 2016). "The scrypt Password-Based Key Derivation Function". tools.ietf.org. doi:10.17487/RFC7914. Retrieved 2016-12-12.
- ^ Mathog, DR (22 September 2003). "Parallel BLAST on split databases". Bioinformatics. 19 (14): 1865–6. doi:10.1093/bioinformatics/btg250. PMID 14512366.
- ^ How we made our face recognizer 25 times faster (developer blog post)
- ^ Shigeyoshi Tsutsui; Pierre Collet (5 December 2013). Massively Parallel Evolutionary Computation on GPGPUs. Springer Science & Business Media. ISBN 978-3-642-37959-8.
- ^ Youssef Hamadi; Lakhdar Sais (5 April 2018). Handbook of Parallel Constraint Reasoning. Springer. ISBN 978-3-319-63516-3.
- ^ Simple Network of Workstations (SNOW) package
External links
[edit]- Embarrassingly Parallel Computations, Engineering a Beowulf-style Compute Cluster
- "Star-P: High Productivity Parallel Computing"
Embarrassingly parallel
View on GrokipediaDefinition and Concepts
Definition
Parallel computing involves the simultaneous use of multiple compute resources, such as processors or cores, to solve a computational problem by dividing it into discrete parts that can be executed concurrently, thereby reducing overall execution time.[6] This approach requires breaking the problem into independent instructions executed on different processing units, coordinated by an overall mechanism to manage the parallelism.[6] Embarrassingly parallel problems, also known as ideally parallel problems, are a subset of parallel computations where the workload can be decomposed into a set of completely independent subtasks that require little or no coordination beyond initial data distribution and final result aggregation.[6][7] In these cases, each subtask operates in isolation without inter-task dependencies, communication, synchronization, or load balancing during execution, distinguishing them from other parallelization models like message-passing systems, which rely on explicit data exchange between processes, or shared-memory parallelism, which necessitates synchronization mechanisms to manage concurrent access to common resources.[6][7][8] The basic workflow for embarrassingly parallel computations typically begins with partitioning the input data into independent subsets, followed by executing each subtask concurrently across multiple processors, and concluding with a simple combination of results, such as summation or concatenation, to form the final output.[1] This structure exploits the obvious concurrency inherent in the problem once tasks are defined, making it straightforward to achieve near-linear speedup with increasing numbers of processors.[1]Key Characteristics
Embarrassingly parallel problems are defined by the fundamental independence of their constituent tasks, where subtasks execute without any need for intercommunication, data sharing, or coordination during computation. This property enables straightforward assignment of tasks to multiple processors, achieving perfect load distribution and scalability limited only by the number of available processing units. As a result, such problems can theoretically utilize all processors fully from the outset, without dependencies that could cause idle time or bottlenecks.[6] A key advantage stems from the minimal overhead associated with parallelization, as there are no communication costs, synchronization barriers, or mechanisms for conflict resolution required. This leads to near-linear speedup in practice, closely approximating the ideal predicted by Amdahl's law when the serial fraction of the computation approaches zero. Under Amdahl's formulation, the speedup for processors is given by where is the serial fraction; for embarrassingly parallel workloads, , yielding . However, real-world implementations may encounter minor limitations from input/output operations or task setup, slightly deviating from perfect linearity.[9][10] Despite these strengths, embarrassingly parallel approaches have notable limitations. If individual tasks are too granular or short-lived, the overhead from task dispatching, memory allocation, and result collection can dominate execution time, eroding efficiency and making parallelization counterproductive. Uneven partitioning of the workload may also introduce load imbalances, where some processors finish early and idle while others process larger shares, necessitating dynamic balancing techniques to mitigate. Fundamentally, these problems are unsuitable for applications with inherent task dependencies, as any required interaction would violate the independence assumption and introduce synchronization challenges.[10][1][6] In terms of scalability, embarrassingly parallel problems particularly benefit from Gustafson's law, which emphasizes scaling problem size alongside processor count to sustain efficiency. This contrasts with Amdahl's focus on fixed-size problems, allowing embarrassingly parallel computations to exploit larger datasets or more iterations with additional resources, achieving speedups that grow with while keeping the scaled serial fraction low.[9]History and Etymology
Origin of the Term
The term "embarrassingly parallel" was coined by Cleve Moler in the mid-1980s while working on parallel computing applications at Intel's Scientific Computers division, particularly in the context of the iPSC Hypercube system. Moler first publicly used the phrase in his presentation titled "Matrix Computation on Distributed Memory Multiprocessors" at the Knoxville Conference on Hypercube Multiprocessors, held in August 1985. He applied it to matrix computations, where many independent tasks could be distributed across multiple processors without inter-processor communication, exemplifying a level of parallelism that required no sophisticated algorithmic redesign. The paper was published in the conference proceedings by SIAM in 1986.[11] The choice of "embarrassing" in the term underscores the trivial nature of parallelizing such problems, implying that the ease borders on being almost too straightforward for the complexities typically associated with parallel algorithms, which often involve challenging issues like load balancing and synchronization. This humorous connotation captured the informal spirit of early discussions in computing conferences, where researchers grappled with harnessing emerging hardware for scientific workloads.[12] Following its introduction, the term rapidly entered the literature of supercomputing in the late 1980s, appearing in papers on applications amenable to hypercube and vector processor architectures, such as Monte Carlo methods for physical simulations. Moler's usage is widely recognized as the origin of the term. The phrase emerged amid the proliferation of massively parallel processing (MPP) systems and early supercomputers in the 1980s and 1990s, highlighting opportunities for simple scaling in contrast to more interdependent computational tasks.Evolution in Parallel Computing
The roots of embarrassingly parallel computing trace back to the 1960s and 1970s, when early multiprocessing systems began enabling the execution of independent tasks without significant inter-process communication. Systems like the Burroughs D825 in 1962, a symmetric MIMD architecture with up to four CPUs connected via a crossbar switch, allowed for parallel processing of separate workloads, laying groundwork for batch processing environments where multiple jobs could run concurrently on shared hardware.[13] In the 1970s, advancements such as the ILLIAC-IV (1972), featuring 64 processing elements, supported massively parallel computations on independent data arrays, while vector processors like the Cray-1 (1976) accelerated embarrassingly parallel operations through pipelined execution of independent vector instructions.[13] These developments, though limited by hardware constraints, highlighted the potential for scaling simple parallel workloads in batch-oriented and early supercomputing contexts.[14] Formal recognition of embarrassingly parallel paradigms emerged in the 1980s alongside the rise of specialized supercomputers, shifting focus toward architectures optimized for independent task distribution. Vector supercomputers from Cray Research, such as the Cray X-MP (1982), enabled efficient handling of data-parallel workloads with minimal synchronization, achieving peak performances like 800 MFLOPS through parallel pipelines.[15] Massively parallel processors (MPPs) like the Connection Machine CM-1 (1985) from Thinking Machines, with 65,536 single-bit processors, further exemplified this by executing vast numbers of independent operations simultaneously, influencing applications in simulation and modeling.[13] By the late 1980s, Amdahl's Law (formalized in 1967 but widely applied then) underscored the efficiency gains for workloads with low communication overhead, solidifying embarrassingly parallel as a key category in parallel computing taxonomies.[13] The 1990s marked widespread adoption through distributed computing, particularly with Beowulf clusters, which democratized access to parallel processing for embarrassingly parallel tasks. Originating at NASA Goddard in 1994, these commodity PC-based clusters interconnected via Ethernet supported scalable execution of independent jobs, such as scientific simulations, without custom hardware, achieving teraflop-scale performance by the decade's end.[16] In the 2000s, grid computing extended this to heterogeneous networks, while frameworks like Hadoop's MapReduce (introduced in 2004) revolutionized big data processing by treating map phases as embarrassingly parallel operations across distributed nodes, enabling petabyte-scale independent task execution with fault tolerance.[17] These milestones emphasized scalability for data-intensive applications, contrasting with earlier communication-bound systems.[18] This evolution influenced parallel computing by promoting a shift from communication-intensive models like MPI, which required explicit synchronization, to data-parallel frameworks that minimized overhead for independent tasks. MapReduce and successors like Apache Spark (2010) prioritized "embarrassingly parallel" map operations over MPI's message-passing, reducing programming complexity for large-scale analytics and achieving near-linear speedups on clusters.[19] By the 2010s, this paradigm contributed to cloud computing's rise, where platforms like AWS and Google Cloud supported elastic allocation for embarrassingly parallel jobs, as seen in hybrid batch systems processing terabytes with sub-minute latencies.[20] Recent developments through 2025 have integrated embarrassingly parallel concepts with AI accelerators, serverless architectures, and edge computing, expanding beyond traditional HPC. GPUs and TPUs, as in modern AI training pipelines, exploit massive parallelism for independent inference tasks, with frameworks like TensorFlow enabling distributed execution across accelerators for workloads scaling to exaflops.[21] Serverless platforms, such as AWS Lambda, have adopted this for real-time embarrassingly parallel problems, like patient monitoring simulations, achieving sub-second latencies for thousands of independent streams without infrastructure management.[22] In edge computing, post-2010 expansions facilitate on-device AI processing, where neuromorphic chips and federated learning handle independent tasks at the network periphery, reducing latency for IoT applications while preserving privacy.[23]Examples
Computational Examples
One classic example of an embarrassingly parallel computation is Monte Carlo integration, where the value of a definite integral is approximated by generating and evaluating numerous independent random samples. In the specific case of estimating π, random points are thrown into a unit square enclosing a quarter-circle, and the ratio of points falling inside the circle to the total points yields an approximation of π/4 after scaling by 4; each point's evaluation is isolated from others, allowing parallel execution across processors with minimal synchronization beyond final averaging.[24][25] The following pseudocode illustrates a parallel implementation for the π approximation using Monte Carlo methods, where random number generation is forked independently per task and results are aggregated:function monte_carlo_pi(num_samples):
inside_count = 0
for i in 1 to num_samples:
x = random_uniform(0, 1)
y = random_uniform(0, 1)
if x² + y² ≤ 1:
inside_count += 1
return 4 * (inside_count / num_samples)
# Parallel version ([pseudocode](/page/Pseudocode)):
parallel_tasks = [fork](/page/Fork)(num_processors)
for task in parallel_tasks:
task_pi = monte_carlo_pi(num_samples / num_processors)
parallel_results = collect(task_pi from all tasks)
pi_estimate = average(parallel_results)
function monte_carlo_pi(num_samples):
inside_count = 0
for i in 1 to num_samples:
x = random_uniform(0, 1)
y = random_uniform(0, 1)
if x² + y² ≤ 1:
inside_count += 1
return 4 * (inside_count / num_samples)
# Parallel version ([pseudocode](/page/Pseudocode)):
parallel_tasks = [fork](/page/Fork)(num_processors)
for task in parallel_tasks:
task_pi = monte_carlo_pi(num_samples / num_processors)
parallel_results = collect(task_pi from all tasks)
pi_estimate = average(parallel_results)
Real-World Applications
Embarrassingly parallel techniques have found widespread application in bioinformatics through projects like Folding@home, which since 2000 has utilized distributed computing to simulate protein folding by running independent trajectory simulations across volunteer-hosted machines, enabling the exploration of vast conformational spaces without inter-task dependencies.[31] These simulations treat each folding trajectory as an autonomous computation, scaling to millions of CPU hours contributed globally to study diseases such as Alzheimer's and COVID-19. In quantitative finance, Monte Carlo methods for portfolio risk assessment exemplify embarrassingly parallel workloads, where thousands of independent simulation paths are generated to model asset price evolutions under stochastic processes, allowing parallel execution on clusters to achieve near-linear speedups in valuing complex derivatives.[32] This approach handles the high dimensionality of financial models by distributing path computations across processors, reducing computation time from days to hours for real-time trading decisions.[33] Search engines leverage embarrassingly parallel processing in web crawling and indexing, as seen in early Google infrastructure using MapReduce to distribute the fetching and parsing of independent web pages across commodity clusters, enabling the scalable indexing of billions of documents.[17] Each mapper processes isolated URLs without synchronization, facilitating efficient handling of the web's growth and supporting rapid query responses.[34] High-throughput genomic sequencing relies on embarrassingly parallel read alignment, where millions of short DNA reads from sequencers are independently mapped to a reference genome using tools like BWA or Bowtie, distributed across compute nodes to process terabytes of data in parallel.[35] This independence allows for straightforward scaling on HPC systems, accelerating variant calling in projects like the 1000 Genomes Project.[36] In the 2020s, climate modeling has increasingly adopted embarrassingly parallel ensemble runs for weather and climate predictions, as in cloud-based systems generating independent simulations of atmospheric variables to quantify uncertainty in forecasts.[37] These ensembles, comprising hundreds of perturbed initial condition runs, enable probabilistic outputs for events like hurricanes, with parallelization on platforms like AWS reducing ensemble creation from weeks to days.[38] Cryptocurrency mining, particularly for proof-of-work blockchains like Bitcoin, operates as an embarrassingly parallel task by distributing nonce hashing attempts across GPU or ASIC arrays, where each core independently computes SHA-256 double hashes without communication until a valid block is found.[39] This structure has driven the proliferation of specialized hardware, with mining pools coordinating parallel efforts to solve blocks in seconds rather than years on single machines.[40]Implementations
Software Approaches
Data-parallel libraries facilitate the implementation of embarrassingly parallel workloads by distributing independent computations across multiple processing units. Apache Spark, an open-source unified analytics engine, supports such workloads through its core abstraction of Resilient Distributed Datasets (RDDs), where transformations likemap and flatMap apply functions independently to each data partition in parallel across a cluster, with minimal coordination beyond data shuffling for subsequent operations. This approach leverages Spark's lazy evaluation to optimize execution, making it ideal for large-scale data processing tasks such as independent simulations or feature extractions on partitioned datasets. Similarly, OpenMP, a standard API for shared-memory multiprocessing, enables loop-level parallelism via the #pragma omp parallel for directive, which automatically divides independent loop iterations among threads without requiring explicit synchronization, as long as iterations have no data dependencies.[41]
High-level frameworks simplify the orchestration of embarrassingly parallel tasks by abstracting away low-level details like thread management or network communication. In Python, the multiprocessing module provides a Pool class for creating worker process pools that execute tasks concurrently, bypassing the Global Interpreter Lock (GIL) and supporting independent function applications to iterables via methods like map or imap, which distribute work evenly across available cores.[42] For distributed environments, Ray, a unified framework for scaling AI and Python applications, implements dynamic task graphs where remote functions (@ray.remote) can be invoked asynchronously and executed in parallel across a cluster with fault tolerance, requiring no inter-task dependencies for embarrassingly parallel scenarios like hyperparameter tuning or Monte Carlo simulations. Dask, another Python-native library, extends NumPy and Pandas to larger-than-memory datasets by building task graphs of delayed computations, allowing seamless scaling from single machines to clusters for independent operations on partitioned arrays or dataframes with minimal synchronization overhead.[43]
Cloud-native tools further democratize embarrassingly parallel execution by providing serverless platforms that automatically scale independent function invocations. AWS Lambda allows developers to deploy functions that run in isolated execution environments, scaling horizontally to handle thousands of concurrent invocations without provisioning infrastructure; each invocation processes an event independently, making it suitable for tasks like image resizing or data validation across distributed inputs.[44] Google Cloud Functions operates similarly, executing event-driven code in a fully managed environment where multiple instances can run in parallel to process independent requests, such as API-triggered computations, with built-in concurrency controls to manage load.
Effective implementation of embarrassingly parallel workloads relies on best practices for workload distribution and result handling. Data partitioning strategies ensure balanced load across processors: round-robin partitioning cyclically assigns data items to partitions for uniform distribution, preventing hotspots in scenarios with variable task durations, while hash-based partitioning uses a hash function on keys to co-locate related data, though it risks skew if keys are unevenly distributed.[45] Results from parallel tasks are typically aggregated using reduction operations, such as summing values from independent computations in Spark's reduce or Dask's compute, which collect and combine outputs post-execution with low overhead.
Post-2020 advancements in containerized environments have enhanced support for embarrassingly parallel jobs through Kubernetes operators, which automate the deployment and scaling of parallel workloads. For instance, Kubernetes Jobs natively support fine-grained parallel processing by launching multiple pods to consume from a shared work queue, enabling independent task execution across nodes; extensions like Argo Workflows, updated in versions post-2020, provide declarative DAGs for orchestrating parallel steps in containerized pipelines, facilitating scalable execution of independent subtasks in cloud-native HPC applications.[46]
