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Contents of /MITgcm/eesupp/inc/GLOBAL_SUM.h

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Revision - (show annotations) (download)
Thu Apr 12 10:52:48 2001 UTC (22 years, 1 month ago) by cnh
Branch: pre38
CVS Tags: pre38tag1, pre38-close
Changes since 1.1: +33 -0 lines
File MIME type: text/plain
Changes to restore/introduce true shared memory (i.e. pure SMP model) support
for lat-lon, cartesian and cube.

 o Threads support restored for global_sum, global_max.
   Needed COMMON blocks in place of stack variables
   for work space.

 o COMMON added for temps that are exchanged
   shap_filt, solve_for_pressure

 o exch...template edits to allow multithreaded calling
   of cube exchanges. Cube exchanges are done single threaded,
   sequential at the moment and are hard coded for six-tile,
   one tile per face configuration.

 o Threading support only tested on Sun SMP (6500) system.

 o Default is SYSTEM() exists (check_threads.F), and barrier and memsync
   are used for threaded exchanges (ini_communications_patterns).

 o Killed K-level plot (ini_masks_etc.F). Overlaps not set in
   multi-threads (local array), so fails in plot_field().

 o Fixed t-ave of phihyd ( DYNAMICS() ). Can only do it for
   first tile.

 o Added commented out nTx settings to hs94.cs-32x32x5 eedata.
   Need to activate for setenv PARALLEL

 o Multi-threaded pickup is 100% validated.

Testing notes

 o Code passes "testscript" tests.

 o To get "hs94.cs-32x32x5" to run OK need to patch
   dynamics.F. Patch is in hs94.cs-32x32x5/code/dynamics.patch.

 o Multithreading only tested on Sun 6500 SMP for hs94.cs and
   hs94.128. hs94.128 was OK at c37 but has a problem under multi-threading
   at pre38 at the moment.

 o Under Solaris need one of
   setenv PARALLEL 2
   setenv PARALLEL 3
   setenv PARALLEL 6
   setenv PARALLEL 8  ( hs94.128 only )
    - and -
   setenv STACKSIZE 16384

 o Under Solaris f77 need to remove -u from Makefile FOPTS for compiling
   fftpack.o. Need to declare everything in fftpack or have
   custom compile options for fftpack.F to fix this.

1 C $Header: /u/gcmpack/models/MITgcmUV/eesupp/inc/BARRIER.h,v 1.3 2001/02/04 14:38:41 cnh Exp $
2 C $Name: checkpoint37 $
3 C
4 C /==========================================================\
5 C | GLOBA:_SUM.h |
6 C | o Globals used by Fortran global sum routine. |
7 C |==========================================================|
8 C | The global sum shared memory scheme uses global heap data|
9 C | structures (.i.e COMMON blocks ). Each thread writes to |
10 C | an its own element of the shared memory array and then |
11 C | one thread reads all the entries and sums them. The sum |
12 C | result is then read by all threads. |
13 C | Remember - you are working with regions of memory that |
14 C | are being updated concurrently by different threads. |
15 C | What happens, when it happens and who gets to see what |
16 C | happens at what stage depends on the computer systems |
17 C | memory model. Every computer has a different memory model|
18 C | and they are never simple. In all current platforms it is|
19 C | possible for one thread to see events happening in a |
20 C | different order from the order they are written in the |
21 C | code. |
22 C | Unless you understand this it is not a good idea to |
23 C | make modifications te way these header files are setup or|
24 C | the way the global sum routines work. |
25 C \==========================================================/
27 Real*8 phiGSRL(lShare8, MAX_NO_THREADS )
30 Real*4 phiGSRS(lShare4, MAX_NO_THREADS )

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