# Why is consistent-consistent mapping not supported in parallel?

**URL:** <https://precice.discourse.group/t/why-is-consistent-consistent-mapping-not-supported-in-parallel/922>\
**Category:** Using preCICE\
**Tags:** data-mapping, parallel\
**Created:** [February 16, 2022, 3:55am UTC](https://precice.discourse.group/t/why-is-consistent-consistent-mapping-not-supported-in-parallel/922 "2022-02-16T03:55:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![belgiansteve](https://avatars.discourse-cdn.com/v4/letter/b/a4c791/32.png) [@belgiansteve](https://precice.discourse.group/u/belgiansteve)\
**Post date:** [February 16, 2022, 3:55am UTC](https://precice.discourse.group/t/why-is-consistent-consistent-mapping-not-supported-in-parallel/922/1 "2022-02-16T03:55:00Z")

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Hi,

We are working on a coupled FSI code where OpenFOAM is coupled via precice to a custom solid mechanics solver. We are interested in using a consistent mapping of stress with a consistent mapping of displacements. Although this method works on a single core, when trying to run in parallel, the following error appears:

[precice] For a parallel participant, only the mapping combinations read-consistent and write-conservative are allowed.

We’d like to understand why this limitation exists, and if there is a work-around? I attached the precice config file. I do want to add that although this particular config file uses nearest-neighbor mapping, we are also interested in nearest-projection mapping.

Any insight is appreciated! TIA!

Steve  
[precice-config.xml](https://precice.discourse.group/uploads/short-url/nhCfv7BcwKMPDqwPjqR3YSb0grL.xml) (2.3 KB)

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**Author:** ![ajaust](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/ajaust/32/160_2.png) [@ajaust](https://precice.discourse.group/u/ajaust)\
**Post date:** [February 16, 2022, 7:27am UTC](https://precice.discourse.group/t/why-is-consistent-consistent-mapping-not-supported-in-parallel/922/2 "2022-02-16T07:27:58Z")

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There is some information in the [preCICE documentation](https://precice.org/configuration-mapping.html#restrictions-for-parallel-participants) and especially in the linked PhD thesis. It also describes a solution to the problem (move the mapping to the other participant to be `read-consistent`).

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/precice/original/1X/67d2a5fa6f80e597e2267ff17fa8c1673cd11caa.svg) [@system](https://precice.discourse.group/u/system)\
**Post date:** [February 22, 2022, 8:16pm UTC](https://precice.discourse.group/t/why-is-consistent-consistent-mapping-not-supported-in-parallel/922/3 "2022-02-22T20:16:45Z")

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