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2021WP/HPC-03_Mele_Comm_Cleanup (diff) – NEMO

Changes between Version 3 and Version 4 of 2021WP/HPC-03_Mele_Comm_Cleanup


Ignore:
Timestamp:
2021-03-15T09:18:59+01:00 (3 years ago)
Author:
epico
Comment:

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  • 2021WP/HPC-03_Mele_Comm_Cleanup

    v3 v4  
    2626=== Implementation 
    2727 
    28 The implementation (or better the rationalization) of the lbc_lnk calls will start from DYN and ZDF modules (the TRA modue 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.  
     28The 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.  
    2929 
    30 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 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. 
     30The 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 ([attachment:NorthFold_and_Halo2.pdf.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. 
    3131 
    32 In order to preserve the bit comparion 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 whith the interested expressions. 
     32In 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. 
    3333 
    34 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 previuos one, but the differences will be only due to the changes in the order of the floating point operations, hence they should be acceptable. 
     34We 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. 
    3535 
    3636