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schism-dev · Dec 19, 2024 · a576255 · a576255
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Showing 4 changed files with 7 additions and 5 deletions.
diff --git a/src/Core/schism_glbl.F90 b/src/Core/schism_glbl.F90
@@ -390,7 +390,7 @@ module schism_glbl
   real(4),save,allocatable :: ath2(:,:,:,:,:) !used to read *.nc for b.c. time series
 #ifdef SH_MEM_COMM
   !Use more efficient share mem communicator for I/O
-  real(4),public,save,pointer :: ath3(:,:,:,:)
+  real(4),save,pointer :: ath3(:,:,:,:)
 #else
   real(4),save,allocatable :: ath3(:,:,:,:) !used to read source/sink inputs
 #endif

diff --git a/src/Core/schism_msgp.F90 b/src/Core/schism_msgp.F90
@@ -452,14 +452,14 @@ subroutine parallel_init(communicator)
     CALL MPI_Comm_size(comm_node, nproc_node, ierr)
     CALL MPI_Comm_rank(comm_node, myrank_node,ierr)
 
-    !Ensure that myrank_node=0 includes myrank=0 for some bcast (read in by
+    !Ensure that myrank_node=0 (nonunique) includes myrank=0 for some bcast (read in by
     !myrank_node=0 and then bcast from myrank=0 in comm)
     if(myrank_node==0.and.myrank==0) then
       itmp=1 !true
     else
       itmp=0
     endif
-    !comm_node seems to cause error, maybe due to non-unique ranks?
+    !Collectives on comm_node won't work as they are on per node basis!
     call mpi_allreduce(itmp,itmp2,1,itype,MPI_SUM,comm,ierr)
     if(itmp2==0) then
       write(*,*)'Ranks:',myrank_node,myrank,itmp,itmp2

diff --git a/src/Hydro/misc_subs.F90 b/src/Hydro/misc_subs.F90
@@ -824,7 +824,8 @@ subroutine other_hot_init(time)
         call mpi_bcast(th_dt3,nthfiles3,rtype,0,comm,istat)
         call mpi_bcast(th_time3,2*nthfiles3,rtype,0,comm,istat)
 #ifdef SH_MEM_COMM
-        !For share mem, ath3 is already filled
+        !For share mem, ath3 is already filled. Collective on comm_node is per node
+        !The barrier may not be necessary
         call mpi_barrier(comm_node, istat)
 #else
         call mpi_bcast(ath3,max(1,nsources,nsinks)*ntracers*2*nthfiles3,MPI_REAL4,0,comm,istat)

diff --git a/src/Hydro/schism_step.F90 b/src/Hydro/schism_step.F90
@@ -1685,7 +1685,8 @@ subroutine schism_step(it)
         call mpi_bcast(th_time3,2*nthfiles3,rtype,0,comm,istat)
 #ifdef SH_MEM_COMM
         ! ath3 data in shared buffer, no longer necessary to broadcast
-        !Sync to ensure the buffer is filled
+        !Sync (on each compute node) to ensure the buffer is filled
+        !The barrier may not be necessary
         call mpi_barrier(comm_node, istat)
 #else
         call mpi_bcast(ath3,max(1,nsources,nsinks)*ntracers*2*nthfiles3,MPI_REAL4,0,comm,istat)