git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@9447 f3b2605a-c512-4ea7-a41b-209d697bcdaa

src/comm.cpp

@@ -1506,12 +1506,15 @@ void Comm::forward_comm_array(int n, double **array)
 
 /* ----------------------------------------------------------------------
    communicate inbuf around full ring of processors with messtag
-   nbytes = size of inbuf = n datums, each of size nper bytes
-   use callback() to allow caller to process each proc's inbuf
+   nbytes = size of inbuf = n datums * nper bytes
+   callback() is invoked to allow caller to process/update each proc's inbuf
+   note that callback() is invoked on final iteration for original inbuf
+   for non-NULL outbuf, final updated inbuf is copied to it
+   outbuf = inbuf is OK
 ------------------------------------------------------------------------- */
 
 void Comm::ring(int n, int nper, void *inbuf, int messtag,
-                void (*callback)(int, char *))
+                void (*callback)(int, char *), void *outbuf)
 {
   MPI_Request request;
   MPI_Status status;
@@ -1537,10 +1540,12 @@ void Comm::ring(int n, int nper, void *inbuf, int messtag,
       MPI_Wait(&request,&status);
       MPI_Get_count(&status,MPI_CHAR,&nbytes);
       memcpy(buf,bufcopy,nbytes);
-      callback(nbytes/nper,buf);
     }
+    callback(nbytes/nper,buf);
   }
 
+  if (outbuf) memcpy(outbuf,buf,nbytes);
+
   memory->destroy(buf);
   memory->destroy(bufcopy);
 }

src/comm.h

@@ -61,7 +61,7 @@ class Comm : protected Pointers {
   virtual void reverse_comm_dump(class Dump *);    // reverse comm from a Dump
   void forward_comm_array(int, double **);         // forward comm of array
 
-  void ring(int, int, void *, int, void (*)(int, char *));   // ring comm
+  void ring(int, int, void *, int, void (*)(int, char *), void *); // ring comm
 
   virtual void set(int, char **);         // set communication style
   void set_processors(int, char **);      // set 3d processor grid attributes

src/special.cpp

@@ -956,7 +956,7 @@ void Special::dihedral_trim()
     if (next == nprocs) next = 0;
     if (prev < 0) prev = nprocs - 1;
 
-    int messtag = 7;
+    int messtag = 8;
     for (int loop = 0; loop < nprocs; loop++) {
       i = 0;
       while (i < size) {