/[MITgcm]/MITgcm/eesupp/inc/BARRIER.h
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Contents of /MITgcm/eesupp/inc/BARRIER.h

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Revision 1.1.1.1 - (show annotations) (download) (vendor branch)
Wed Apr 22 19:15:30 1998 UTC (25 years, 10 months ago) by cnh
Branch: cnh
CVS Tags: baseline, start
Changes since 1.1: +0 -0 lines
File MIME type: text/plain
Imported working release

1 C $Id$
2 C
3 C /==========================================================\
4 C | FBAR.h |
5 C | o Globals used by Fortran barrier routine. |
6 C |==========================================================|
7 C | These variables support a simple Fortran shared memory |
8 C | barrier routine. They do busy waiting, that is the |
9 C | thread that is waiting sits in a tight loop reading |
10 C | some memory location and waiting for all other threads. |
11 C | On some systems this is sometimes a good method to use. |
12 C | On the T3E memory is not shared so the routine should |
13 C | use the T3E "eureka" barriers. On CRAY and NEC there are |
14 C | hardware barriers that are accessed through a compiler |
15 C | directives. Finally proper multi-threading compilers |
16 C | support barrier compile directives - sometimes these |
17 C | are good, sometimes they are lousy. |
18 C | The barrier mechanism is used as follows |
19 C | 1. In the single-threaded part of the code |
20 C | CALL FBAR_INIT |
21 C | on CRAY, NEC this routine does nothing |
22 C | on T3E there is no single-threaded code |
23 C | but there may be barrier initialisation - |
24 C | need to check. |
25 C | 2. When we need to synchronize everybody just |
26 C | CALL FBAR( myThid ) |
27 C | where myThid is myThreadId |
28 C | on CRAY, NEC FBAR will just do C$DIR BARRIER |
29 C | or the like. |
30 C | on T3E FBAR does CALL BARRIER(...) or something |
31 C | need to check this. |
32 C \==========================================================/
33 COMMON / BARRIER_COMMON / key1, key2, key3,
34 & door1, door2, door3
35 INTEGER key1(lShare4,MAX_NO_THREADS)
36 INTEGER key2(lShare4,MAX_NO_THREADS)
37 INTEGER key3(lShare4,MAX_NO_THREADS)
38 INTEGER door1
39 INTEGER door2
40 INTEGER door3
41 INTEGER VALID
42 PARAMETER ( VALID = 1 )
43 INTEGER INVALID
44 PARAMETER ( INVALID = 0 )
45 INTEGER OPEN
46 PARAMETER ( OPEN = 1 )
47 INTEGER SHUT
48 PARAMETER ( SHUT = 0 )

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