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coarray fortran wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 implementation in compilers 2 examples 3 an alternate perspective 4 see also 5 references toggle references subsection 5 1 general toggle the table of contents coarray fortran 3 languages deutsch 日本語 українська edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia fortran parallel programming extension this article has multiple issues please help improve it or discuss these issues on the talk page learn how and when to remove these messages this article includes a list of general references but lacks sufficient corresponding inline citations please help improve this article by introducing more precise citations august 2011 learn how and when to remove this message this article may lack focus or be about more than one topic please help improve this article possibly by splitting it or creating a disambiguation page relevant discussion may be found on the talk page november 2021 learn how and when to remove this message learn how and when to remove this message coarray fortran paradigm multi paradigm parallel message passing imperative procedural object oriented structured designed by robert numrich and john reid developer pl22 3 fortran committee stable release fortran 2008 iso iec 1539 1 2010 typing discipline strong static os cross platform major implementations cray g95 gnu fortran intel fortran compiler rice caf 2 0 openuh nag fortran compiler influenced by fortran coarray fortran caf formerly known as f started as an extension of fortran 95 2003 for parallel processing created by robert numrich and john reid in the 1990s the fortran 2008 standard iso iec 1539 1 2010 now includes coarrays spelled without hyphen as decided at the may 2005 meeting of the iso fortran committee the syntax in the fortran 2008 standard is slightly different from the original caf proposal a caf program is interpreted as if it were replicated a number of times and all copies were executed asynchronously each copy has its own set of data objects and is termed an image the array syntax of fortran is extended with additional trailing subscripts in square brackets to provide a concise representation of references to data that is spread across images the caf extension was implemented in some fortran compilers such as those from cray since release 3 1 since the inclusion of coarrays in the fortran 2008 standard the number of implementations is growing the first open source compiler which implemented coarrays as specified in the fortran 2008 standard for linux architectures is g95 currently gnu fortran provides wide coverage of fortran s coarray features in single and multi image configuration the latter based on the opencoarrays library another implementation of coarrays and related parallel extensions from fortran 2008 is available in the openuh compiler a branch of open64 developed at the university of houston implementation in compilers edit caf is often implemented on top of a message passing interface mpi library for portability some implementations such as the ones available in the gnu fortran and openuh compilers may run on top of other low level layers for example gasnet designed for supporting partitioned global address space languages examples edit a simple example is given below caf is used in cgpack an open source package for simulating polycrystalline materials developed at the university of bristol 1 program hello_world implicit none integer i local variable character len 20 name scalar coarray one name for each image note name is the local variable while name index accesses the variable in a specific image name this_image is the same as name interact with the user on image 1 execution for all others pass by if this_image 1 then write a advance no enter your name read a name distribute information to other images do i 2 num_images name i name end do end if sync all barrier to make sure the data have arrived i o from all images executing in any order but each record written is intact write 3a i0 hello trim name from image this_image end program hello_world the program above scales poorly because the loop that distributes information executes sequentially writing scalable programs often requires a sophisticated understanding of parallel algorithms a detailed knowledge of the underlying network characteristics and special tuning for application characteristics such as the size of data transfers for most application developers letting the compiler or runtime library decide the best algorithm proves more robust and high performing fortran 2018 will offer collective communication subroutines that empower compiler and runtime library teams to encapsulate efficient parallel algorithms for collective communication and distributed computation in a set of collective subroutines these subroutines and other new parallel programming features are summarized in a technical specification 2 that the fortran standards committee has voted to incorporate into fortran 2018 these enable the user to write a more efficient version of the above algorithm program hello_world implicit none character len 20 name scalar coarray one name for each image note name is the local variable while name index accesses the variable in a specific image name this_image is the same as name interact with the user on image 1 execution for all others pass by if this_image 1 then write a advance no enter your name read a name end if distribute information to all images call co_broadcast name source_image 1 i o from all images executing in any order but each record written is intact write 3a i0 hello trim name from image this_image end program hello_world where the lack of explicit synchronization offers the potential for higher performance due to less coordination between the images furthermore ts 18508 guarantees that a transfer from an image cannot occur before the collective subroutine has been invoked on that image this implies some partial synchronization inside co_broadcast but could be higher performing than the sync all in the prior example ts 18508 also incorporates several other new features that address issues targeted by the caf 2 0 effort described below examples include teams of images and events an alternate perspective edit this section may be unbalanced towards certain viewpoints please help improve it by adding information on neglected viewpoints relevant discussion may be found on the talk page september 2018 this section may rely excessively on sources too closely associated with the subject potentially preventing it from being verifiable and neutral please help improve this article by replacing such sources with more appropriate citations to reliable independent sources november 2021 learn how and when to remove this message in 2011 rice university pursued an alternate vision of coarray extensions for the fortran language 3 their perspective is that the fortran 2008 standard committee s design choices were shaped more by the desire to introduce as few modifications to the language as possible than to assemble the best set of extensions to support parallel programming in their view both numrich and reid s original design and the coarray extensions proposed for fortran 2008 suffer from the following shortcomings there is no support for processor subsets for instance coarrays must be allocated over all images the coarray extensions lack any notion of global pointers which are essential for creating and manipulating any kind of linked data structure reliance on named critical sections for mutual exclusion hinders scalable parallelism by associating mutual exclusion with code regions rather than data objects fortran 2008 s sync images statement does not provide a safe synchronization space as a result synchronization operations in user s code that are pending when a library call is made can interfere with synchronization in the library call there are no mechanisms to avoid or tolerate latency when manipulating data on remote images there is no support for collective communication to address these shortcomings the rice university group is developing a clean slate redesign of the coarray fortran programming model rice s new design for coarray fortran which they call coarray fortran 2 0 is an expressive set of coarray based extensions to fortran designed to provide a productive parallel programming model compared to fortran 2008 rice s new coarray based language extensions include some additional features process subsets known as teams which support coarrays collective communication and relative indexing of process images for pair wise operations topologies which augment teams with a logical communication structure dynamic allocation deallocation of coarrays and other shared data team based coarray allocation and deallocation global pointers in support of dynamic data structures support for latency hiding and avoidance and asynchronous copies asynchronous collective operations and function shipping enhanced support for synchronization for fine grain control over program execution safe and scalable support for mutual exclusion including locks and lock sets events which provide a safe space for point to point synchronization cofence which forces local completion of asynchronous operations finish a barrier like spmd construct that forces completion of asynchronous operations across a team see also edit array programming chapel fortress parallel computing partitioned global address space unified parallel c x10 references edit a shterenlikht fortran coarray library for 3d cellular automata microstructure simulation archived 2016 03 04 at the wayback machine 2013 in proc 7th pgas conf eds m weiland a jackson n johnson published by the university of edinburgh isbn 978 0 9926615 0 2 ts 18508 additional parallel features in fortran coarray fortran 2 0 general edit iso fortran committee archived 2011 04 23 at the wayback machine ansi incits fortran committee instructional videos on caf in the fortran standard by john reid see appendix b coarray in gnu fortran coarraylib in gnu fortran opencoarrays library nag fortran compiler v t e parallel computing general distributed computing parallel computing parallel algorithm massively parallel cloud computing high performance computing multiprocessing manycore processor gpgpu computer network systolic array levels bit instruction thread task data memory loop pipeline multithreading temporal simultaneous smt simultaneous and heterogenous speculative spmt preemptive cooperative clustered multi thread cmt hardware scout theory pram model pem model analysis of parallel algorithms amdahl s law gustafson s law cost efficiency karp flatt metric slowdown speedup elements process thread fiber instruction window array coordination multiprocessing memory coherence cache coherence cache invalidation barrier synchronization application checkpointing programming stream processing dataflow programming models implicit parallelism explicit parallelism concurrency non blocking algorithm hardware flynn s taxonomy sisd simd array processing simt pipelined processing associative processing misd mimd dataflow architecture pipelined processor superscalar processor vector processor multiprocessor symmetric asymmetric memory shared distributed distributed shared uma numa coma massively parallel computer computer cluster beowulf cluster grid computer hardware acceleration apis ateji px boost chapel hpx charm cilk coarray fortran cuda dryad c amp global arrays gpuopen mpi openmp opencl openhmpp openacc parallel extensions pvm pthreads raftlib rocm upc tbb zpl problems automatic parallelization cache stampede deadlock deterministic algorithm embarrassingly parallel parallel slowdown race condition software lockout scalability starvation category parallel computing retrieved from https en wikipedia org w index php title coarray_fortran oldid 1375542344 category fortran programming language family hidden categories articles with short description short description is different from wikidata articles lacking in text citations from august 2011 all articles lacking in text citations wikipedia articles lacking focus from november 2021 all wikipedia articles lacking focus articles with multiple maintenance issues webarchive template wayback links articles needing more viewpoints from september 2018 articles lacking reliable references from november 2021 all articles lacking reliable references this page was last edited on 18 september 2026 at 12 46 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is a registered trademark of the wikimedia foundation inc a non profit organization privacy policy about wikipedia disclaimers contact wikipedia legal safety contacts code of conduct developers statistics cookie statement mobile view search search toggle the table of contents coarray fortran 3 languages add topic