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Manycore processors are special kinds of multi-core processors designed for a high degree of parallel processing, containing numerous simpler, independent processor cores (from a few tens of cores to thousands or more). Manycore processors are used extensively in embedded computers and high-performance computing.

Contrast with multicore architecture

Manycore processors are distinct from multi-core processors in being optimized from the outset for a higher degree of explicit parallelism, and for higher throughput (or lower power consumption) at the expense of latency and lower single-thread performance.

The broader category of multi-core processors, by contrast, are usually designed to efficiently run both parallel and serial code, and therefore place more emphasis on high single-thread performance (e.g. devoting more silicon to out-of-order execution, deeper pipelines, more superscalar execution units, and larger, more general caches), and shared memory. These techniques devote runtime resources toward figuring out implicit parallelism in a single thread. They are used in systems where they have evolved continuously (with backward compatibility) from single core processors. They usually have a 'few' cores (e.g. 2, 4, 8) and may be complemented by a manycore accelerator (such as a GPU) in a heterogeneous system.

Motivation

Cache coherency is an issue limiting the scaling of multicore processors. Manycore processors may bypass this with methods such as message passing,^[1] scratchpad memory, DMA,^[2] partitioned global address space,^[3] or read-only/non-coherent caches. A manycore processor using a network on a chip and local memories gives software the opportunity to explicitly optimise the spatial layout of tasks (e.g. as seen in tooling developed for TrueNorth).^[4]

Manycore processors may have more in common (conceptually) with technologies originating in high-performance computing such as clusters and vector processors.^[5]

GPUs may be considered a form of manycore processor having multiple shader processing units, and only being suitable for highly parallel code (high throughput, but extremely poor single thread performance).

Suitable programming models

• Message passing interface
• OpenCL^[6] or other APIs supporting compute kernels
• Partitioned global address space
• Actor model
• OpenMP^[7]
• Dataflow

Classes of manycore systems

• GPUs, which can be described as manycore vector processors
• Massively parallel processor array
• Asynchronous array of simple processors

Specific manycore architectures

• ZettaScaler [1], Japanese PEZY Computing 2,048-core modules
• Xeon Phi coprocessor, which has MIC (Many Integrated Cores) architecture
• Tilera
• Adapteva Epiphany Architecture, a manycore chip using PGAS scratchpad memory
• Coherent Logix hx3100 Processor, a 100-core DSP/GPP processor based on HyperX Architecture
• Movidius Myriad 2, a manycore vision processing unit (VPU)
• Kalray, a manycore PCI-e accelerator for data-intensive tasks
• Teraflops Research Chip, a manycore processor using message passing
• TrueNorth, an AI accelerator with a manycore network on a chip architecture
• Green arrays, a manycore processor using message passing aimed at low power applications
• Sunway SW26010, a 260-core manycore processor used in the then top 1 supercomputer Sunway TaihuLight
  • SW52020, an improved 520-core^[8][9] variant of SW26010, with 512-bit SIMD (also adding support for half-precision), used in a prototype, meant for an exascale system (and in the future 10 exascale system), and according to datacenterdynamics China is rumored to already have two separate exascale systems secretly^{[citation needed]}
• Eyeriss, a manycore processor designed for running convolutional neural nets for embedded vision applications^[10]
• Graphcore, a manycore AI accelerator

Specific manycore computers with 1M+ CPU cores

A number of computers built from multicore processors have one million or more individual CPU cores. Examples include:

• Gyoukou (Japanese: 暁光 Hepburn: gyōkō, dawn light), a supercomputer developed by ExaScaler and PEZY Computing, with 20,480,000 processing elements total plus the 1,250 Intel Xeon D host processors.
• SpiNNaker, a massively parallel (1 million CPU cores) manycore processor (ARM-based) built as part of the Human Brain Project.

Specific computers with 5 million or more CPU cores

Quite a few supercomputers have over 5 million CPU cores. When there are also coprocessors, e.g. GPUs used with, then those cores are not listed in the core-count, then quite a few more computers would hit those targets.

• Frontier
• Fugaku, a Japanese supercomputer using Fujitsu A64FX ARM-based cores, 7,630,848 in total.
• Sunway TaihuLight, a massively parallel (10 million CPU cores) Chinese supercomputer, once one of the fastest supercomputers in the world, using a custom manycore architecture.^{[citation needed]} As of November 2018, it was the world's third fastest supercomputer (as ranked by the TOP500 list), obtaining its performance from 40,960 SW26010 manycore processors, each containing 256 cores.

See also

• Multi-core processor
• Vector processor
• SIMD
• High-performance computing
• Computer cluster
• Multiprocessor system on a chip
• Vision processing unit
• Memory access pattern
• Cache coherency
• Embarrassingly parallel
• Massively parallel
• CUDA

References

External links

• Architecting solutions for the Manycore future, published on Feb 19, 2010 (more than one dead link in the slide)
• Eyeriss architecture