Changes between Version 2 and Version 3 of Ticket #552


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Timestamp:
05/13/12 02:11:09 (13 years ago)
Author:
arango
Comment:

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  • Ticket #552 – Description

    v2 v3  
    1 This update includes a full revision of ROMS shared-memory pragma directives using '''OpenMP''' standard.  This is a very important and delicate update that requires expertise.  Luckly, I doubth that will affect you customized code.
     1This update includes a full revision of ROMS shared-memory pragma directives using '''OpenMP''' standard.  This is a very important and delicate update that requires expertise.  Luckly, I doubth that will affect your customized code.
    22
    33All the parallel loops of ROMS are modified to simpler directives.  For example, the old strategy:
    … …  
    1919!$OMP BARRIER
    2020}}}
    21 In shared-memory, the parallel threads are spawn at higher calling routines.  For example, we now have:
     21In shared-memory, the parallel threads are spawn in the higher calling routines (drivers).  For example, we now have:
    2222{{{
    2323!$OMP PARALLEL
    2424      CALL main3d (RunInterval)
    25 #endif
    2625!$OMP END PARALLEL
    2726}}}
    28 This directive is less restrictive and allows '''MASTER''', '''BARRIER''', and other useful '''OpenMP''' pragmas inside the parallel region.  If you are interested, please see the following discussion in the [https://www.myroms.org/forum/viewtopic.php?f=19&t=2584 Forum].
     27This directive is less restrictive and allows '''MASTER''', '''BARRIER''', and other useful '''OpenMP''' pragmas inside the parallel regions.  If you are interested, please see the following discussion in the [https://www.myroms.org/forum/viewtopic.php?f=19&t=2584 Forum].
    2928
    3029This change cleans the code and facilitates parallelization of tricky algorithms for nesting, '''MPDATA''', random number generation, point-sources, etc using the shared-memory paradigm.
    … …  
    3231'''WARNINGS:'''
    3332
    34   * The values of '''NtileX(ng)''' and '''NtileE(ng)''' are no longer equal to '''one''' in distributed-memory ('''MPI''').  They have the same values as the one specified in standard input '''NtileI(ng)''' and '''NtileJ(ng)'''. Notice that in the critical regions for global reduction operatios we now use instead the following code:
     33  * The values of '''NtileX(ng)''' and '''NtileE(ng)''' are no longer equal to '''one''' in distributed-memory ('''MPI''').  They have the same values as the ones specified in standard input: '''NtileI(ng)''' and '''NtileJ(ng)'''. Notice that in the critical regions for global reduction operations, we now use the following code instead:
    3534{{{
    3635#ifdef DISTRIBUTE
    … …  
    4544#endif
    4645}}}
    47   That is, we do a special exception for distribute-memory.  This change is necessary in your customized versions of '''ana_grid.h''' and '''ana_psource.h'''.
     46  That is, we do a special exception for distribute-memory cases.  This change is necessary in your customized versions of '''ana_grid.h''' and '''ana_psource.h'''.
    4847
    49   * Notice that we no longer use '''TILE''' (uppercase) as argument to the kernel routines.  We use '''tile''' (lowercase) instead. This was important in previous versions for distributed-memory since '''TILE''' was replaced to '''!MyRank''' during C-preprocessing.  Be careful with this one...
     48  * Notice that we no longer use the '''TILE''' (uppercase) as argument to the kernel routines.  We use '''tile''' (lowercase) instead. This was important in previous versions of distributed-memory code where '''TILE''' was replaced with '''!MyRank''' during C-preprocessing.  Be careful with this one...
    5049
    5150  * Notice that few important variables of ROMS in '''mod_scalars.F''' and '''mod_stepping.F''' use the '''THREADPRIVATE''' directive in shared-memory so all the parallel threads have a private copy of such variables to avoid parallel collisions.