diff --git a/src/fix_shake.cpp b/src/fix_shake.cpp
index ac877f0bcc..589fd83af8 100644
--- a/src/fix_shake.cpp
+++ b/src/fix_shake.cpp
@@ -38,6 +38,10 @@ using namespace LAMMPS_NS;
 using namespace FixConst;
 using namespace MathConst;
 
+// allocate space for static class variable
+
+FixShake *FixShake::fsptr;
+
 #define BIG 1.0e20
 #define MASSDELTA 0.1
 
@@ -521,7 +525,7 @@ void FixShake::post_force(int vflag)
   int m;
   for (int i = 0; i < nlist; i++) {
     m = list[i];
-    if (shake_flag[m] == 2) shake2(m);
+    if (shake_flag[m] == 2) shake(m);
     else if (shake_flag[m] == 3) shake3(m);
     else if (shake_flag[m] == 4) shake4(m);
     else shake3angle(m);
@@ -560,7 +564,7 @@ void FixShake::post_force_respa(int vflag, int ilevel, int iloop)
   int m;
   for (int i = 0; i < nlist; i++) {
     m = list[i];
-    if (shake_flag[m] == 2) shake2(m);
+    if (shake_flag[m] == 2) shake(m);
     else if (shake_flag[m] == 3) shake3(m);
     else if (shake_flag[m] == 4) shake4(m);
     else shake3angle(m);
@@ -656,7 +660,7 @@ void FixShake::find_clusters()
   int max = 0;
   for (i = 0; i < nlocal; i++) max = MAX(max,nspecial[i][0]);
 
-  int *npartner,*nshake;
+  int *npartner;
   memory->create(npartner,nlocal,"shake:npartner");
   memory->create(nshake,nlocal,"shake:nshake");
 
@@ -719,10 +723,7 @@ void FixShake::find_clusters()
     }
   }
 
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"shake:buf");
 
   // fill buffer with info
 
@@ -745,39 +746,9 @@ void FixShake::find_clusters()
   }
 
   // cycle buffer around ring of procs back to self
-  // when receive buffer, scan bond partner IDs for atoms I own
-  // if I own partner:
-  //   fill in mask and type and massflag
-  //   search for bond with 1st atom and fill in bondtype
 
-  messtag = 1;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      m = atom->map(buf[i+1]);
-      if (m >= 0 && m < nlocal) {
-        buf[i+2] = mask[m];
-        buf[i+3] = type[m];
-        if (nmass) {
-          if (rmass) massone = rmass[m];
-          else massone = mass[type[m]];
-          buf[i+4] = masscheck(massone);
-        }
-        if (buf[i+5] == 0) {
-          n = bondfind(m,buf[i],buf[i+1]);
-          if (n >= 0) buf[i+5] = bond_type[m][n];
-        }
-      }
-      i += nper;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  fsptr = this;
+  comm->ring(size,sizeof(int),buf,1,ring_bonds,buf);
 
   // store partner info returned to me
 
@@ -793,8 +764,7 @@ void FixShake::find_clusters()
     m += nper;
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // error check for unfilled partner info
   // if partner_type not set, is an error
@@ -885,10 +855,7 @@ void FixShake::find_clusters()
     }
   }
 
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"shake:buf");
 
   // fill buffer with info
 
@@ -905,28 +872,12 @@ void FixShake::find_clusters()
   }
 
   // cycle buffer around ring of procs back to self
-  // when receive buffer, scan bond partner IDs for atoms I own
-  // if I own partner, fill in nshake value
 
-  messtag = 2;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      m = atom->map(buf[i+1]);
-      if (m >= 0 && m < nlocal) buf[i+2] = nshake[m];
-      i += 3;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  fsptr = this;
+  comm->ring(size,sizeof(int),buf,2,ring_nshake,buf);
 
   // store partner info returned to me
-
+  
   m = 0;
   while (m < size) {
     i = atom->map(buf[m]);
@@ -936,8 +887,7 @@ void FixShake::find_clusters()
     m += 3;
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // -----------------------------------------------------
   // error checks
@@ -1050,10 +1000,7 @@ void FixShake::find_clusters()
     }
   }
 
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"shake:buf");
 
   // fill buffer with info
 
@@ -1079,37 +1026,11 @@ void FixShake::find_clusters()
   }
 
   // cycle buffer around ring of procs back to self
-  // when receive buffer, scan for ID that I own
-  // if I own ID, fill in shake array values
 
-  messtag = 3;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      m = atom->map(buf[i]);
-      if (m >= 0 && m < nlocal) {
-        shake_flag[m] = buf[i+1];
-        shake_atom[m][0] = buf[i+2];
-        shake_atom[m][1] = buf[i+3];
-        shake_atom[m][2] = buf[i+4];
-        shake_atom[m][3] = buf[i+5];
-        shake_type[m][0] = buf[i+6];
-        shake_type[m][1] = buf[i+7];
-        shake_type[m][2] = buf[i+8];
-      }
-      i += 9;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  fsptr = this;
+  comm->ring(size,sizeof(int),buf,3,ring_shake,NULL);
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // -----------------------------------------------------
   // free local memory
@@ -1196,6 +1117,99 @@ void FixShake::find_clusters()
   }
 }
 
+/* ----------------------------------------------------------------------
+   when receive buffer, scan bond partner IDs for atoms I own
+   if I own partner:
+     fill in mask and type and massflag
+     search for bond with 1st atom and fill in bondtype
+------------------------------------------------------------------------- */
+
+void FixShake::ring_bonds(int ndatum, char *cbuf)
+{
+  Atom *atom = fsptr->atom;
+  double *rmass = atom->rmass;
+  double *mass = atom->mass;
+  int *mask = atom->mask;
+  int **bond_type = atom->bond_type;
+  int *type = atom->type;
+  int nlocal = atom->nlocal;
+  int nmass = fsptr->nmass;
+
+  int *buf = (int *) cbuf;
+  int m,n;
+  double massone;
+
+  for (int i = 0; i < ndatum; i += 6) {
+    m = atom->map(buf[i+1]);
+    if (m >= 0 && m < nlocal) {
+      buf[i+2] = mask[m];
+      buf[i+3] = type[m];
+      if (nmass) {
+        if (rmass) massone = rmass[m];
+        else massone = mass[type[m]];
+        buf[i+4] = fsptr->masscheck(massone);
+      }
+      if (buf[i+5] == 0) {
+        n = fsptr->bondfind(m,buf[i],buf[i+1]);
+        if (n >= 0) buf[i+5] = bond_type[m][n];
+      }
+    }
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan bond partner IDs for atoms I own
+   if I own partner, fill in nshake value
+------------------------------------------------------------------------- */
+
+void FixShake::ring_nshake(int ndatum, char *cbuf)
+{
+  Atom *atom = fsptr->atom;
+  int nlocal = atom->nlocal;
+
+  int *nshake = fsptr->nshake;
+
+  int *buf = (int *) cbuf;
+  int m;
+
+  for (int i = 0; i < ndatum; i += 3) {
+    m = atom->map(buf[i+1]);
+    if (m >= 0 && m < nlocal) buf[i+2] = nshake[m];
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan bond partner IDs for atoms I own
+   if I own partner, fill in nshake value
+------------------------------------------------------------------------- */
+
+void FixShake::ring_shake(int ndatum, char *cbuf)
+{
+  Atom *atom = fsptr->atom;
+  int nlocal = atom->nlocal;
+
+  int *shake_flag = fsptr->shake_flag;
+  int **shake_atom = fsptr->shake_atom;
+  int **shake_type = fsptr->shake_type;
+
+  int *buf = (int *) cbuf;
+  int m;
+
+  for (int i = 0; i < ndatum; i += 9) {
+    m = atom->map(buf[i]);
+    if (m >= 0 && m < nlocal) {
+      shake_flag[m] = buf[i+1];
+      shake_atom[m][0] = buf[i+2];
+      shake_atom[m][1] = buf[i+3];
+      shake_atom[m][2] = buf[i+4];
+      shake_atom[m][3] = buf[i+5];
+      shake_type[m][0] = buf[i+6];
+      shake_type[m][1] = buf[i+7];
+      shake_type[m][2] = buf[i+8];
+    }
+  }
+}
+
 /* ----------------------------------------------------------------------
    check if massone is within MASSDELTA of any mass in mass_list
    return 1 if yes, 0 if not
@@ -1252,7 +1266,7 @@ void FixShake::unconstrained_update_respa(int ilevel)
   // for levels > 0 this includes more than one velocity update
   // xshake = predicted position from call to this routine at level N =
   // x + dt0 (v + dtN/m fN + 1/2 dt(N-1)/m f(N-1) + ... + 1/2 dt0/m f0)
-  // also set dtfsq = dt0*dtN so that shake2,shake3,etc can use it
+  // also set dtfsq = dt0*dtN so that shake,shake3,etc can use it
 
   double ***f_level = ((FixRespa *) modify->fix[ifix_respa])->f_level;
   dtfsq = dtf_inner * step_respa[ilevel];
@@ -1298,7 +1312,7 @@ void FixShake::unconstrained_update_respa(int ilevel)
 
 /* ---------------------------------------------------------------------- */
 
-void FixShake::shake2(int m)
+void FixShake::shake(int m)
 {
   int nlist,list[2];
   double v[6];
diff --git a/src/fix_shake.h b/src/fix_shake.h
index c10d8c127f..fcd2a93f38 100644
--- a/src/fix_shake.h
+++ b/src/fix_shake.h
@@ -82,6 +82,7 @@ class FixShake : public Fix {
                                          // for angle cluster, 3rd value
                                          //   is angletype
   double **xshake;                       // unconstrained atom coords
+  int *nshake;                           // count
 
   int vflag;                            // virial flag
   double dtv,dtfsq;                     // timesteps for trial move
@@ -102,13 +103,21 @@ class FixShake : public Fix {
   int masscheck(double);
   void unconstrained_update();
   void unconstrained_update_respa(int);
-  void shake2(int);
+  void shake(int);
   void shake3(int);
   void shake4(int);
   void shake3angle(int);
   void stats();
   int bondfind(int, int, int);
   int anglefind(int, int, int);
+
+  // static variable for ring communication callback to access class data
+  // callback functions for ring communication
+
+  static FixShake *fsptr;
+  static void ring_bonds(int, char *);
+  static void ring_nshake(int, char *);
+  static void ring_shake(int, char *);
 };
 
 }
diff --git a/src/read_data.cpp b/src/read_data.cpp
index 0065472021..f03805cbca 100644
--- a/src/read_data.cpp
+++ b/src/read_data.cpp
@@ -34,9 +34,9 @@
 #include "angle.h"
 #include "dihedral.h"
 #include "improper.h"
+#include "special.h"
 #include "error.h"
 #include "memory.h"
-#include "special.h"
 
 using namespace LAMMPS_NS;
 
diff --git a/src/special.cpp b/src/special.cpp
index eb7d8f826f..5bcb4265b5 100644
--- a/src/special.cpp
+++ b/src/special.cpp
@@ -17,11 +17,16 @@
 #include "atom.h"
 #include "atom_vec.h"
 #include "force.h"
+#include "comm.h"
 #include "memory.h"
 #include "error.h"
 
 using namespace LAMMPS_NS;
 
+// allocate space for static class variable
+
+Special *Special::sptr;
+
 /* ---------------------------------------------------------------------- */
 
 Special::Special(LAMMPS *lmp) : Pointers(lmp)
@@ -49,10 +54,9 @@ Special::~Special()
 
 void Special::build()
 {
-  int i,j,k,m,n,loop,size,original;
-  int num12,num13,num14;
-  int max,maxall,messtag,nbuf,nbufmax;
-  int *buf,*bufcopy,*count;
+  int i,j,k,m,n,size;
+  int max,maxall,nbuf;
+  int *buf;
   MPI_Request request;
   MPI_Status status;
 
@@ -100,10 +104,7 @@ void Special::build()
 
     nbuf = 0;
     for (i = 0; i < nlocal; i++) nbuf += num_bond[i];
-    MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-    buf = new int[nbufmax];
-    bufcopy = new int[nbufmax];
+    memory->create(buf,nbuf,"special:buf");
 
     // fill buffer with global tags of bond partners of my atoms
 
@@ -116,23 +117,10 @@ void Special::build()
     // when receive buffer, scan tags for atoms I own
     // when find one, increment nspecial count for that atom
 
-    messtag = 1;
-    for (loop = 0; loop < nprocs; loop++) {
-      for (i = 0; i < size; i++) {
-        m = atom->map(buf[i]);
-        if (m >= 0 && m < nlocal) nspecial[m][0]++;
-      }
-      if (me != next) {
-        MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-        MPI_Send(buf,size,MPI_INT,next,messtag,world);
-        MPI_Wait(&request,&status);
-        MPI_Get_count(&status,MPI_INT,&size);
-        for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-      }
-    }
+    sptr = this;
+    comm->ring(size,sizeof(int),buf,1,ring_one,NULL);
 
-    delete [] buf;
-    delete [] bufcopy;
+    memory->destroy(buf);
   }
 
   // ----------------------------------------------------
@@ -153,7 +141,7 @@ void Special::build()
 
   // count = accumulating counter
 
-  count = new int[nlocal];
+  memory->create(count,nlocal,"special:count");
   for (i = 0; i < nlocal; i++) count[i] = 0;
 
   // add bond partners stored by atom to onetwo list
@@ -172,10 +160,7 @@ void Special::build()
 
     nbuf = 0;
     for (i = 0; i < nlocal; i++) nbuf += 2*num_bond[i];
-    MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-    buf = new int[nbufmax];
-    bufcopy = new int[nbufmax];
+    memory->create(buf,nbuf,"special:buf");
 
     // fill buffer with global tags of both atoms in bond
 
@@ -190,26 +175,13 @@ void Special::build()
     // when receive buffer, scan 2nd-atom tags for atoms I own
     // when find one, add 1st-atom tag to onetwo list for 2nd atom
 
-    messtag = 2;
-    for (loop = 0; loop < nprocs; loop++) {
-      for (i = 1; i < size; i += 2) {
-        m = atom->map(buf[i]);
-        if (m >= 0 && m < nlocal) onetwo[m][count[m]++] = buf[i-1];
-      }
-      if (me != next) {
-        MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-        MPI_Send(buf,size,MPI_INT,next,messtag,world);
-        MPI_Wait(&request,&status);
-        MPI_Get_count(&status,MPI_INT,&size);
-        for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-      }
-    }
+    sptr = this;
+    comm->ring(size,sizeof(int),buf,2,ring_two,NULL);
 
-    delete [] buf;
-    delete [] bufcopy;
+    memory->destroy(buf);
   }
 
-  delete [] count;
+  memory->destroy(count);
 
   // -----------------------------------------------------
   // done if special_bonds for 1-3, 1-4 are set to 1.0
@@ -230,10 +202,7 @@ void Special::build()
 
   nbuf = 0;
   for (i = 0; i < nlocal; i++) nbuf += 2 + nspecial[i][0];
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"special:buf");
 
   // fill buffer with:
   // (1) = counter for 1-3 neighbors, initialized to 0
@@ -252,27 +221,8 @@ void Special::build()
   // when find one, increment 1-3 count by # of 1-2 neighbors of my atom,
   //   subtracting one since my list will contain original atom
 
-  messtag = 3;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      n = buf[i];
-      num12 = buf[i+1];
-      for (j = 0; j < num12; j++) {
-        m = atom->map(buf[i+2+j]);
-        if (m >= 0 && m < nlocal) n += nspecial[m][0] - 1;
-      }
-      buf[i] = n;
-      i += 2 + num12;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  sptr = this;
+  comm->ring(size,sizeof(int),buf,3,ring_three,buf);
 
   // extract count from buffer that has cycled back to me
   // nspecial[i][1] = # of 1-3 neighbors of atom i
@@ -283,8 +233,7 @@ void Special::build()
     j += 2 + nspecial[i][0];
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // ----------------------------------------------------
   // create onethree[i] = list of 1-3 neighbors for atom i
@@ -307,10 +256,7 @@ void Special::build()
 
   nbuf = 0;
   for (i = 0; i < nlocal; i++) nbuf += 4 + nspecial[i][0] + nspecial[i][1];
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"special:buf");
 
   // fill buffer with:
   // (1) = global tag of original atom
@@ -337,32 +283,8 @@ void Special::build()
   //   exclude the atom whose tag = original
   //   this process may include duplicates but they will be culled later
 
-  messtag = 4;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      original = buf[i];
-      num12 = buf[i+1];
-      num13 = buf[i+2];
-      n = buf[i+3];
-      for (j = 0; j < num12; j++) {
-        m = atom->map(buf[i+4+j]);
-        if (m >= 0 && m < nlocal)
-          for (k = 0; k < nspecial[m][0]; k++)
-            if (onetwo[m][k] != original)
-              buf[i+4+num12+(n++)] = onetwo[m][k];
-      }
-      buf[i+3] = n;
-      i += 4 + num12 + num13;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  sptr = this;
+  comm->ring(size,sizeof(int),buf,4,ring_four,buf);
 
   // fill onethree with buffer values that have been returned to me
   // sanity check: accumulated buf[i+3] count should equal
@@ -377,8 +299,7 @@ void Special::build()
       onethree[i][k] = buf[j++];
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // done if special_bonds for 1-4 are set to 1.0
 
@@ -397,10 +318,7 @@ void Special::build()
 
   nbuf = 0;
   for (i = 0; i < nlocal; i++) nbuf += 2 + nspecial[i][1];
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"special:buf");
 
   // fill buffer with:
   // (1) = counter for 1-4 neighbors, initialized to 0
@@ -419,27 +337,8 @@ void Special::build()
   // when find one, increment 1-4 count by # of 1-2 neighbors of my atom
   //   may include duplicates and original atom but they will be culled later
 
-  messtag = 5;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      n = buf[i];
-      num13 = buf[i+1];
-      for (j = 0; j < num13; j++) {
-        m = atom->map(buf[i+2+j]);
-        if (m >= 0 && m < nlocal) n += nspecial[m][0];
-      }
-      buf[i] = n;
-      i += 2 + num13;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  sptr = this;
+  comm->ring(size,sizeof(int),buf,5,ring_five,buf);
 
   // extract count from buffer that has cycled back to me
   // nspecial[i][2] = # of 1-4 neighbors of atom i
@@ -450,8 +349,7 @@ void Special::build()
     j += 2 + nspecial[i][1];
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   // ----------------------------------------------------
   // create onefour[i] = list of 1-4 neighbors for atom i
@@ -475,10 +373,7 @@ void Special::build()
   nbuf = 0;
   for (i = 0; i < nlocal; i++)
     nbuf += 3 + nspecial[i][1] + nspecial[i][2];
-  MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-  buf = new int[nbufmax];
-  bufcopy = new int[nbufmax];
+  memory->create(buf,nbuf,"special:buf");
 
   // fill buffer with:
   // (1) = # of 1-3 neighbors
@@ -502,30 +397,8 @@ void Special::build()
   //   incrementing the count in buf(i+4)
   //   this process may include duplicates but they will be culled later
 
-  messtag = 6;
-  for (loop = 0; loop < nprocs; loop++) {
-    i = 0;
-    while (i < size) {
-      num13 = buf[i];
-      num14 = buf[i+1];
-      n = buf[i+2];
-      for (j = 0; j < num13; j++) {
-        m = atom->map(buf[i+3+j]);
-        if (m >= 0 && m < nlocal)
-          for (k = 0; k < nspecial[m][0]; k++)
-            buf[i+3+num13+(n++)] = onetwo[m][k];
-      }
-      buf[i+2] = n;
-      i += 3 + num13 + num14;
-    }
-    if (me != next) {
-      MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-      MPI_Send(buf,size,MPI_INT,next,messtag,world);
-      MPI_Wait(&request,&status);
-      MPI_Get_count(&status,MPI_INT,&size);
-      for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-    }
-  }
+  sptr = this;
+  comm->ring(size,sizeof(int),buf,6,ring_six,buf);
 
   // fill onefour with buffer values that have been returned to me
   // sanity check: accumulated buf[i+2] count should equal
@@ -540,8 +413,7 @@ void Special::build()
       onefour[i][k] = buf[j++];
   }
 
-  delete [] buf;
-  delete [] bufcopy;
+  memory->destroy(buf);
 
   combine();
   if (force->special_angle) angle_trim();
@@ -699,7 +571,7 @@ void Special::combine()
 
 void Special::angle_trim()
 {
-  int i,j,m,n,iglobal,jglobal,ilocal,jlocal;
+  int i,j,m,n;
   MPI_Request request;
   MPI_Status status;
 
@@ -743,7 +615,6 @@ void Special::angle_trim()
     int maxcount = 0;
     for (i = 0; i < nlocal; i++)
       maxcount = MAX(maxcount,nspecial[i][1]-nspecial[i][0]);
-    int **dflag;
     memory->create(dflag,nlocal,maxcount,"special::dflag");
 
     for (i = 0; i < nlocal; i++) {
@@ -757,12 +628,8 @@ void Special::angle_trim()
 
     int nbuf = 0;
     for (i = 0; i < nlocal; i++) nbuf += 2*num_angle[i] + 2*2*num_dihedral[i];
-
-    int nbufmax;
-    MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-    int *buf = new int[nbufmax];
-    int *bufcopy = new int[nbufmax];
+    int *buf;
+    memory->create(buf,nbuf,"special:buf");
 
     // fill buffer with list of 1,3 atoms in each angle
     // and with list of 1,3 and 2,4 atoms in each dihedral
@@ -785,41 +652,8 @@ void Special::angle_trim()
     // when receive buffer, scan list of 1,3 atoms looking for atoms I own
     // when find one, scan its 1-3 neigh list and mark I,J as in an angle
 
-    int next = me + 1;
-    int prev = me -1;
-    if (next == nprocs) next = 0;
-    if (prev < 0) prev = nprocs - 1;
-
-    int messtag = 7;
-    for (int loop = 0; loop < nprocs; loop++) {
-      i = 0;
-      while (i < size) {
-        iglobal = buf[i];
-        jglobal = buf[i+1];
-        ilocal = atom->map(iglobal);
-        jlocal = atom->map(jglobal);
-        if (ilocal >= 0 && ilocal < nlocal)
-          for (m = nspecial[ilocal][0]; m < nspecial[ilocal][1]; m++)
-            if (jglobal == special[ilocal][m]) {
-              dflag[ilocal][m-nspecial[ilocal][0]] = 1;
-              break;
-            }
-        if (jlocal >= 0 && jlocal < nlocal)
-          for (m = nspecial[jlocal][0]; m < nspecial[jlocal][1]; m++)
-            if (iglobal == special[jlocal][m]) {
-              dflag[jlocal][m-nspecial[jlocal][0]] = 1;
-              break;
-            }
-        i += 2;
-      }
-      if (me != next) {
-        MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-        MPI_Send(buf,size,MPI_INT,next,messtag,world);
-        MPI_Wait(&request,&status);
-        MPI_Get_count(&status,MPI_INT,&size);
-        for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-      }
-    }
+    sptr = this;
+    comm->ring(size,sizeof(int),buf,7,ring_seven,NULL);
 
     // delete 1-3 neighbors if they are not flagged in dflag
     // preserve 1-4 neighbors
@@ -839,8 +673,7 @@ void Special::angle_trim()
     // clean up
 
     memory->destroy(dflag);
-    delete [] buf;
-    delete [] bufcopy;
+    memory->destroy(buf);
 
   // if no angles or dihedrals are defined,
   // delete all 1-3 neighs, preserving 1-4 neighs
@@ -880,7 +713,7 @@ void Special::angle_trim()
 
 void Special::dihedral_trim()
 {
-  int i,j,m,n,iglobal,jglobal,ilocal,jlocal;
+  int i,j,m,n;
   MPI_Request request;
   MPI_Status status;
 
@@ -918,7 +751,6 @@ void Special::dihedral_trim()
     int maxcount = 0;
     for (i = 0; i < nlocal; i++)
       maxcount = MAX(maxcount,nspecial[i][2]-nspecial[i][1]);
-    int **dflag;
     memory->create(dflag,nlocal,maxcount,"special::dflag");
 
     for (i = 0; i < nlocal; i++) {
@@ -931,12 +763,8 @@ void Special::dihedral_trim()
 
     int nbuf = 0;
     for (i = 0; i < nlocal; i++) nbuf += 2*num_dihedral[i];
-
-    int nbufmax;
-    MPI_Allreduce(&nbuf,&nbufmax,1,MPI_INT,MPI_MAX,world);
-
-    int *buf = new int[nbufmax];
-    int *bufcopy = new int[nbufmax];
+    int *buf;
+    memory->create(buf,nbuf,"special:buf");
 
     // fill buffer with list of 1,4 atoms in each dihedral
 
@@ -951,41 +779,8 @@ void Special::dihedral_trim()
     // when receive buffer, scan list of 1,4 atoms looking for atoms I own
     // when find one, scan its 1-4 neigh list and mark I,J as in a dihedral
 
-    int next = me + 1;
-    int prev = me -1;
-    if (next == nprocs) next = 0;
-    if (prev < 0) prev = nprocs - 1;
-
-    int messtag = 8;
-    for (int loop = 0; loop < nprocs; loop++) {
-      i = 0;
-      while (i < size) {
-        iglobal = buf[i];
-        jglobal = buf[i+1];
-        ilocal = atom->map(iglobal);
-        jlocal = atom->map(jglobal);
-        if (ilocal >= 0 && ilocal < nlocal)
-          for (m = nspecial[ilocal][1]; m < nspecial[ilocal][2]; m++)
-            if (jglobal == special[ilocal][m]) {
-              dflag[ilocal][m-nspecial[ilocal][1]] = 1;
-              break;
-            }
-        if (jlocal >= 0 && jlocal < nlocal)
-          for (m = nspecial[jlocal][1]; m < nspecial[jlocal][2]; m++)
-            if (iglobal == special[jlocal][m]) {
-              dflag[jlocal][m-nspecial[jlocal][1]] = 1;
-              break;
-            }
-        i += 2;
-      }
-      if (me != next) {
-        MPI_Irecv(bufcopy,nbufmax,MPI_INT,prev,messtag,world,&request);
-        MPI_Send(buf,size,MPI_INT,next,messtag,world);
-        MPI_Wait(&request,&status);
-        MPI_Get_count(&status,MPI_INT,&size);
-        for (j = 0; j < size; j++) buf[j] = bufcopy[j];
-      }
-    }
+    sptr = this;
+    comm->ring(size,sizeof(int),buf,8,ring_eight,NULL);
 
     // delete 1-4 neighbors if they are not flagged in dflag
 
@@ -1000,8 +795,7 @@ void Special::dihedral_trim()
     // clean up
 
     memory->destroy(dflag);
-    delete [] buf;
-    delete [] bufcopy;
+    memory->destroy(buf);
 
   // if no dihedrals are defined, delete all 1-4 neighs
 
@@ -1024,3 +818,254 @@ void Special::dihedral_trim()
               "  %g = # of 1-4 neighbors after dihedral trim\n",allcount);
   }
 }
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan tags for atoms I own
+   when find one, increment nspecial count for that atom
+------------------------------------------------------------------------- */
+
+void Special::ring_one(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int nlocal = atom->nlocal;
+
+  int *buf = (int *) cbuf;
+  int m;
+
+  for (int i = 0; i < ndatum; i++) {
+    m = atom->map(buf[i]);
+    if (m >= 0 && m < nlocal) nspecial[m][0]++;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan 2nd-atom tags for atoms I own
+   when find one, add 1st-atom tag to onetwo list for 2nd atom
+------------------------------------------------------------------------- */
+
+void Special::ring_two(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int nlocal = atom->nlocal;
+
+  int **onetwo = sptr->onetwo;
+  int *count = sptr->count;
+
+  int *buf = (int *) cbuf;
+  int m;
+
+  for (int i = 1; i < ndatum; i += 2) {
+    m = atom->map(buf[i]);
+    if (m >= 0 && m < nlocal) onetwo[m][count[m]++] = buf[i-1];
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan list of 1-2 neighbors for atoms I own
+   when find one, increment 1-3 count by # of 1-2 neighbors of my atom,
+     subtracting one since my list will contain original atom
+------------------------------------------------------------------------- */
+
+void Special::ring_three(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int nlocal = atom->nlocal;
+
+  int *buf = (int *) cbuf;
+  int i,j,m,n,num12;
+
+  i = 0;
+  while (i < ndatum) {
+    n = buf[i];
+    num12 = buf[i+1];
+    for (j = 0; j < num12; j++) {
+      m = atom->map(buf[i+2+j]);
+      if (m >= 0 && m < nlocal) n += nspecial[m][0] - 1;
+    }
+    buf[i] = n;
+    i += 2 + num12;
+  }
+}
+
+/* ----------------------------------------------------------------------
+  when receive buffer, scan list of 1-2 neighbors for atoms I own
+  when find one, add its neighbors to 1-3 list
+    increment the count in buf(i+4)
+    exclude the atom whose tag = original
+    this process may include duplicates but they will be culled later
+------------------------------------------------------------------------- */
+
+void Special::ring_four(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int nlocal = atom->nlocal;
+
+  int **onetwo = sptr->onetwo;
+
+  int *buf = (int *) cbuf;
+  int i,j,k,m,n,original,num12,num13;
+
+  i = 0;
+  while (i < ndatum) {
+    original = buf[i];
+    num12 = buf[i+1];
+    num13 = buf[i+2];
+    n = buf[i+3];
+    for (j = 0; j < num12; j++) {
+      m = atom->map(buf[i+4+j]);
+      if (m >= 0 && m < nlocal)
+        for (k = 0; k < nspecial[m][0]; k++)
+          if (onetwo[m][k] != original)
+            buf[i+4+num12+(n++)] = onetwo[m][k];
+    }
+    buf[i+3] = n;
+    i += 4 + num12 + num13;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan list of 1-3 neighbors for atoms I own
+   when find one, increment 1-4 count by # of 1-2 neighbors of my atom
+     may include duplicates and original atom but they will be culled later
+------------------------------------------------------------------------- */
+
+void Special::ring_five(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int nlocal = atom->nlocal;
+
+  int *buf = (int *) cbuf;
+  int i,j,m,n,num13;
+
+  i = 0;
+  while (i < ndatum) {
+    n = buf[i];
+    num13 = buf[i+1];
+    for (j = 0; j < num13; j++) {
+      m = atom->map(buf[i+2+j]);
+      if (m >= 0 && m < nlocal) n += nspecial[m][0];
+    }
+      buf[i] = n;
+      i += 2 + num13;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan list of 1-3 neighbors for atoms I own
+   when find one, add its neighbors to 1-4 list
+     incrementing the count in buf(i+4)
+     this process may include duplicates but they will be culled later
+------------------------------------------------------------------------- */
+
+void Special::ring_six(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int nlocal = atom->nlocal;
+
+  int **onetwo = sptr->onetwo;
+
+  int *buf = (int *) cbuf;
+  int i,j,k,m,n,num13,num14;
+
+  i = 0;
+  while (i < ndatum) {
+    num13 = buf[i];
+    num14 = buf[i+1];
+    n = buf[i+2];
+    for (j = 0; j < num13; j++) {
+      m = atom->map(buf[i+3+j]);
+      if (m >= 0 && m < nlocal)
+        for (k = 0; k < nspecial[m][0]; k++)
+          buf[i+3+num13+(n++)] = onetwo[m][k];
+    }
+    buf[i+2] = n;
+    i += 3 + num13 + num14;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan list of 1,3 atoms looking for atoms I own
+   when find one, scan its 1-3 neigh list and mark I,J as in an angle
+------------------------------------------------------------------------- */
+
+void Special::ring_seven(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int **special = atom->special;
+  int nlocal = atom->nlocal;
+
+  int **dflag = sptr->dflag;
+
+  int *buf = (int *) cbuf;
+  int i,m,iglobal,jglobal,ilocal,jlocal;
+
+  i = 0;
+  while (i < ndatum) {
+    iglobal = buf[i];
+    jglobal = buf[i+1];
+    ilocal = atom->map(iglobal);
+    jlocal = atom->map(jglobal);
+    if (ilocal >= 0 && ilocal < nlocal)
+      for (m = nspecial[ilocal][0]; m < nspecial[ilocal][1]; m++)
+        if (jglobal == special[ilocal][m]) {
+          dflag[ilocal][m-nspecial[ilocal][0]] = 1;
+          break;
+        }
+    if (jlocal >= 0 && jlocal < nlocal)
+      for (m = nspecial[jlocal][0]; m < nspecial[jlocal][1]; m++)
+        if (iglobal == special[jlocal][m]) {
+          dflag[jlocal][m-nspecial[jlocal][0]] = 1;
+          break;
+        }
+    i += 2;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   when receive buffer, scan list of 1,4 atoms looking for atoms I own
+   when find one, scan its 1-4 neigh list and mark I,J as in a dihedral
+------------------------------------------------------------------------- */
+
+void Special::ring_eight(int ndatum, char *cbuf)
+{
+  Atom *atom = sptr->atom;
+  int **nspecial = atom->nspecial;
+  int **special = atom->special;
+  int nlocal = atom->nlocal;
+
+  int **dflag = sptr->dflag;
+
+  int *buf = (int *) cbuf;
+  int i,m,iglobal,jglobal,ilocal,jlocal;
+
+  i = 0;
+  while (i < ndatum) {
+    iglobal = buf[i];
+    jglobal = buf[i+1];
+    ilocal = atom->map(iglobal);
+    jlocal = atom->map(jglobal);
+    if (ilocal >= 0 && ilocal < nlocal)
+      for (m = nspecial[ilocal][1]; m < nspecial[ilocal][2]; m++)
+        if (jglobal == special[ilocal][m]) {
+          dflag[ilocal][m-nspecial[ilocal][1]] = 1;
+          break;
+        }
+    if (jlocal >= 0 && jlocal < nlocal)
+      for (m = nspecial[jlocal][1]; m < nspecial[jlocal][2]; m++)
+        if (iglobal == special[jlocal][m]) {
+          dflag[jlocal][m-nspecial[jlocal][1]] = 1;
+          break;
+        }
+    i += 2;
+  }
+}
+
+
+
+
diff --git a/src/special.h b/src/special.h
index b550f1ac47..6d07cf00dd 100644
--- a/src/special.h
+++ b/src/special.h
@@ -29,9 +29,27 @@ class Special : protected Pointers {
   int **onetwo,**onethree,**onefour;
   int dihedral_flag;
 
+  // data used by ring callback methods
+
+  int *count;
+  int **dflag;
+
   void combine();
   void angle_trim();
   void dihedral_trim();
+
+  // static variable for ring communication callback to access class data
+  // callback functions for ring communication
+
+  static Special *sptr;
+  static void ring_one(int, char *);
+  static void ring_two(int, char *);
+  static void ring_three(int, char *);
+  static void ring_four(int, char *);
+  static void ring_five(int, char *);
+  static void ring_six(int, char *);
+  static void ring_seven(int, char *);
+  static void ring_eight(int, char *);
 };
 
 }