/[MITgcm]/MITgcm/eesupp/src/barrier.F

Diff of /MITgcm/eesupp/src/barrier.F

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-revision 1.13 by cnh,
Tue Nov  8 15:53:41 2005 UTC
+revision 1.14 by jmc,
Tue Aug  4 18:01:37 2009 UTC
 Line 55 
 C     !INTERFACE:
  C     !DESCRIPTION:
  C     *==========================================================*
  C     | SUBROUTINE BARRIER
  C     | o Barrier routine that uses "busy waiting".
  C     *==========================================================*
  C     | This routine provides a pure fortran mechanism to
  C     | synchronise multiple threads in a multi-threaded code.
  C     | No thread can leave this routine before all the threads
  C     | have entered it.
  C     | Notes
  C     | =====
  C     | The door and key variables are assumed to have been
  C     | initialized once an initial state of key = INVALID
  C     | and door = SHUT.
  C     | We use the routine FOOL\_THE\_COMPILER to stop compilers
  C     | generating code which might simply set and test a
  C     | register value. Shared-memory systems only maintain
  C     | coherency over process caches and not registers.
  C     | Also we have to be a bit careful regarding sequential
  C     | consistency - or lack of it. At the moment the code
  C     | assumes a total store order memory model, which some
  C     | machines do not have! However, I have yet to find a
  C     | problem with this I think because the tolerances in
  C     | terms of memory ordering i.e. a little bit of reordering
  C     | probably will not break the barrier mechanism!
  C     | On non-cache coherent systems e.g. T3E we need to use
  C     | a library function to do barriers.
  C     | Note - The PANIC tests can be removed for working code
  C     |        I have left them in without an ifdef option
  C     |        because without them programming errors can
  C     |        lead to infinitely spinning code. If you are
  C     |        confident that your code is OK then removing
  C     |        them may increase performance. Do not remove these
  C     |        lines to make your code "work" If the code is
  C     |        stopping in these PANIC blocks then something is
  C     |        wrong with your program and it needs to be fixed.
  C     *==========================================================*
  C     !USES:
 Line 104 
 C     == Routine arguments ==
  C     !LOCAL VARIABLES:
  C     === Local variables ===
  C     nDone :: Counter for number of threads that have
  C              completed a section.
  C     I     :: Loop counter
        INTEGER nDone
 Line 119 
 CcnhDebugEnds
  C$OMP BARRIER
        bCount(myThid) = bCount(myThid) + 1
        IF ( masterSet(myThid) .NE. 0 ) THEN
         PRINT *, 'BARRIER called for master reg myThid == ',
       &   myThid, masterSet(myThid)
        ENDIF
  Cdbg C$OMP BARRIER
 Line 141 
 Cdbg C$OMP BARRIER
  C--   Check that thread number is expected range
        IF ( myThid .LT. 1 .OR. myThid .GT. nThreads ) THEN
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! CATASTROPHIC ERROR'
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! in S/R BARRIER  myThid = ',
       &  myThid, ' nThreads = ', nThreads
         STOP 'ABNROMAL END: S/R BARRIER'
        ENDIF
 Line 149 
 C--   Check that thread number is expect
  C--   When every threads key1 is valid thread 1 will open door1.
        IF ( key1(1,myThid) .EQ. VALID ) THEN
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! CATASTROPHIC ERROR'
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! in S/R BARRIER  myThid = ',
       &  myThid, ' key1 already validated'
         STOP 'ABNROMAL END: S/R BARRIER'
        ENDIF
 Line 161 
 C--   When every threads key1 is valid t
          DO I=1,nThreads
           if ( key1(1,I) .EQ. VALID ) nDone = nDone+1
          ENDDO
-         CALL FOOL_THE_COMPILER( key1 )
+         CALL FOOL_THE_COMPILER( key1(1,1) )
         IF ( nDone .LT. nThreads ) GOTO 10
         door1 = OPEN
        ELSE
 Line 189 
 C--   door3 because they have to go thro
  C--   When every threads key2 is valid thread 1 will open door2.
  C     Notes
  C     =====
  C     I think that to work with any memory model ( i.e. relaxed,
  C     partial store, total store) the variables key1, key2 and key3
  C     might need to be set to invalid by thread 1.
  C
        IF ( key2(1,myThid) .EQ. VALID ) THEN
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! CATASTROPHIC ERROR'
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! in S/R BARRIER  myThid = ',
       &  myThid, ' key2 already validated'
         STOP 'ABNROMAL END: S/R BARRIER'
        ENDIF
 Line 207 
 C
          DO I=1,nThreads
           if ( key2(1,I) .EQ. VALID ) nDone = nDone+1
          ENDDO
-         CALL FOOL_THE_COMPILER( key2 )
+         CALL FOOL_THE_COMPILER( key2(1,1) )
         IF ( nDone .LT. nThreads ) GOTO 20
         door2 = OPEN
        ELSE
 Line 226 
 C--   door1 because they have to go thro
        IF ( myThid .EQ. 1 ) THEN
         door1 = SHUT
        ENDIF
  C--   When every threads key3 is valid thread 1 will open door3.
        IF ( key3(1,myThid) .EQ. VALID ) THEN
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! CATASTROPHIC ERROR'
         WRITE(*,*) '!!!!!!! PANIC !!!!!!! in S/R BARRIER  myThid = ',
       &  myThid, ' key3 already validated'
         STOP 'ABNROMAL END: S/R BARRIER'
        ENDIF
 Line 243 
 C
          DO I=1,nThreads
           if ( key3(1,I) .EQ. VALID ) nDone = nDone+1
          ENDDO
-         CALL FOOL_THE_COMPILER( key3 )
+         CALL FOOL_THE_COMPILER( key3(1,1) )
         IF ( nDone .LT. nThreads ) GOTO 30
         door3 = OPEN
        ELSE
 Line 266 
 C--   door2 because they have to go thro
  CcnhDebugStarts
  C      WRITE(myThid,*) ' Barrier exited '
  CcnhDebugEnds
        RETURN
        END

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