| Version 6 (modified by epico, 3 years ago) (diff) |
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Name and subject of the action
Last edition: Wikinfo(changed_ts)? by Wikinfo(changed_by)?
The PI is responsible to closely follow the progress of the action, and especially to contact NEMO project manager if the delay on preview (or review) are longer than the 2 weeks expected.
Summary
| Action | Communications cleanup |
|---|---|
| PI(S) | Francesca Mele, Italo Epicoco |
| Digest | This task concerns the removal/shifting of unnecessary communications within routines when using halo 2. |
| Dependencies | |
| Branch | source:/NEMO/branches/2021/dev_r14393_HPC-03_Mele_Comm_Cleanup |
| Previewer(s) | TDB |
| Reviewer(s) | TBD |
| Ticket | #2607 |
Description
This action aims at completing what was stared in 2020. Due to the halo=2 most of the lbc_lnk communications can be removed or moved earlier in the code. A careful analysis of the DO LOOP ranges leads the removal of the useless lbc_lnk calls as well.
Implementation
The implementation (or better the rationalization) of the lbc_lnk calls will start from DYN and ZDF modules (the TRA module was completed in 2020). Because we decided to support halo=1 execution, we put the lbc_lnk call inside of an IF statement condition whenever needed.
The movement of a communication earlier in the code (in the case of halo=2) often leads to a difference in the outputs when compared with the halo=1 run. This is due to the north folding algorithm. In the attached document (and Halo2.pdf) we analysed the problem and found that, due to the north fold, some expressions are evalauted correctly but with a different order of the floating point operations with respect the halo=1 case.
In order to preserve the bit comparison of the results between the cases halo=1 and halo=2, we have to "force" the order of the floating point operations in both cases by introducing round brackets whithin the interested expressions.
We propose to insert the round brackets in the expressions where needed directly into the trunk. This will cause a version of the trunk which is not bit comparable with the previous one, but the differences will be only due to the changes in the order of the floating point operations, hence they should be acceptable.
Documentation updates
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Preview
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Tests
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Review
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Attachments (1)
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NorthFold and Halo2.pdf
(841.4 KB) -
added by epico 3 years ago.
North Fold and Halo 2
Download all attachments as: .zip
