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bar2.F
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C $Header: /u/gcmpack/MITgcm/eesupp/src/bar2.F,v 1.7 2009/08/04 18:01:37 jmc Exp $
C $Name: $
#include "CPP_EEOPTIONS.h"
CBOP
C !ROUTINE: BAR2_INIT
C !INTERFACE:
SUBROUTINE BAR2_INIT( myThid )
IMPLICIT NONE
C !DESCRIPTION:
C *=====================================================================*
C | SUBROUTINE BAR2\_INIT
C | o Setup global barrier data structures.
C *=====================================================================*
C | Initialise global barrier data structures that can be used in
C | conjunction with MPI or that can also be used to create
C *=====================================================================*
C !USES:
C == Global variables ==
#include "SIZE.h"
#include "EEPARAMS.h"
#include "EESUPPORT.h"
#include "BAR2.h"
C
C !INPUT/OUTPUT PARAMETERS:
C == Routine arguments ==
C myThid :: Thread number of this instance of BAR2_INIT
INTEGER myThid
C !LOCAL VARIABLES:
C == Local variables ==
C I :: Loop counter
INTEGER I
CEOP
C
DO I = 1, lShare4
BAR2_level(I,myThid) = 0
BAR2_barrierCount(I,myThid) = 0
BAR2_spinsCount(I,myThid) = 0
BAR2_spinsCount(I,myThid) = 0
BAR2_spinsMax (I,myThid) = 0
BAR2_spinsMin (I,myThid) = 1000000000
ENDDO
C
bar2CollectStatistics = .TRUE.
C
RETURN
END
CBOP
C !ROUTINE: BAR2
C !INTERFACE:
SUBROUTINE BAR2( myThid )
IMPLICIT NONE
C !DESCRIPTION:
C *=====================================================================*
C | SUBROUTINE BAR2
C | o Global barrier routine.
C *=====================================================================*
C | Implements a simple true shared memory barrier that uses a global
C | heap array that all threads can access to synchronise. Each thread
C | writes to a predefined location. One thread polls the locations. Other
C | threads poll an all clear assertion location. Once the polling
C | thread that is looping over locations sees writes for each thread is
C | writes the all clear assertion location and everyone proceeds. A
C | cyclic series of locations is used to ensure that race conditions do
C | not occur. A few simple statistics are recorded giving number of
C | barrier calls, max, min and aggregate polling loop counts.
C *=====================================================================*
C !USES:
C == Global variables ==
#include "SIZE.h"
#include "EEPARAMS.h"
#include "EESUPPORT.h"
#include "BAR2.h"
C !INPUT/OUTPUT PARAMETERS:
C == Routine arguments ==
C myThid :: Thread number of this instance of BAR2
INTEGER myThid
C !LOCAL VARIABLES:
C == Local variables ==
C myLevel :: Temp. to hold "active" barrier level
C nDone :: Temp. for counting number of threads that
C have reached the barrier.
C I :: Loop counter
C spinCount :: Temp. for doing statistics on how many
C times barrier code looped.
INTEGER myLevel
INTEGER nDone
INTEGER I
INTEGER spinCount
CEOP
#ifdef USE_OMP_THREADING
C$OMP BARRIER
BAR2_barrierCount(1,myThid) = BAR2_barrierCount(1,myThid)+1
Cdbg C$OMP BARRIER
Cdbg DO I = 2, nThreads
Cdbg IF ( BAR2_barrierCount(1,I) .NE. BAR2_barrierCount(1,1) ) THEN
Cdbg PRINT *, BAR2_barrierCount(1,1:nThreads)
Cdbg CALL SYSTEM('sleep 1')
Cdbg PRINT *, BAR2_barrierCount(1,1:nThreads)
Cdbg Stop ' bar2 OUT OF SYNC '
Cdbg ENDIF
Cdbg ENDDO
Cdbg C$OMP BARRIER
RETURN
#endif
spinCount = 0
IF ( myThid .NE. 1 ) THEN
BAR2_level(1,myThid) = BAR2_level(1,myThid)+1
myLevel = BAR2_level(1,myThid)
10 CONTINUE
IF ( BAR2_level(1,1) .EQ. myLevel ) GOTO 11
spinCount = spinCount+1
CALL FOOL_THE_COMPILER( BAR2_level(1,1) )
GOTO 10
11 CONTINUE
ELSE
myLevel = BAR2_level(1,1)
12 CONTINUE
CALL FOOL_THE_COMPILER( BAR2_level(1,1) )
nDone = 1
DO I = 2, nThreads
IF ( BAR2_level(1,1) .EQ. BAR2_level(1,I)-1 ) nDone = nDone+1
ENDDO
spinCount = spinCount+1
IF ( nDone .LT. nThreads ) GOTO 12
BAR2_level(1,1) = myLevel+1
ENDIF
BAR2_barrierCount(1,myThid) = BAR2_barrierCount(1,myThid)+1
BAR2_spinsCount(1,myThid) = BAR2_spinsCount(1,myThid)+spinCount
BAR2_spinsMax (1,myThid) = MAX(BAR2_spinsMax(1,myThid),spinCount)
BAR2_spinsMin (1,myThid) = MIN(BAR2_spinsMin(1,myThid),spinCount)
RETURN
END

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