diff --git a/C/c_interface.c b/C/c_interface.c
index 268c700a7..9beec3e9e 100644
--- a/C/c_interface.c
+++ b/C/c_interface.c
@@ -556,6 +556,7 @@ X_API void    *STD_PROTO(YAP_OpaqueObjectFromTerm,(Term));
 X_API int      STD_PROTO(YAP_Argv,(char *** argvp));
 X_API YAP_tag_t STD_PROTO(YAP_TagOfTerm,(Term));
 X_API size_t   STD_PROTO(YAP_ExportTerm,(Term, char *, size_t));
+X_API size_t   STD_PROTO(YAP_SizeOfExportedTerm,(char *));
 X_API Term     STD_PROTO(YAP_ImportTerm,(char *));
 
 static UInt
@@ -4008,10 +4009,14 @@ YAP_ExportTerm(Term inp, char * buf, size_t len) {
   size_t res;
   if (!len)
     return 0;
-  if ((res = Yap_ExportTerm(inp, buf, len, current_arity())) < 0) {
-    exit(1);
-  }
-  return res;
+  return Yap_ExportTerm(inp, buf, len, current_arity());
+}
+
+X_API size_t
+YAP_SizeOfExportedTerm(char * buf) {
+  if (!buf)
+    return 0;
+  return Yap_SizeOfExportedTerm(buf);
 }
 
 X_API Term
diff --git a/C/utilpreds.c b/C/utilpreds.c
index db5838c68..788fdf393 100644
--- a/C/utilpreds.c
+++ b/C/utilpreds.c
@@ -1168,7 +1168,7 @@ CELL *CellDifH(CELL *hptr, CELL *hlow)
   return (CELL *)((char *)hptr-(char *)hlow);
 }
 
-#define AdjustSizeAtom(X)	((char *)(((CELL)X+7) & (CELL)(-8)))
+#define AdjustSizeAtom(X)	((char *)(((CELL)(X)+(8-1)) & ~(8-1)))
 
 static inline 
 Atom export_atom(Atom at, char **hpp, char *buf, size_t len)
@@ -1648,6 +1648,13 @@ Yap_ImportTerm(char * buf) {
   return tret;
 }
 
+size_t
+Yap_SizeOfExportedTerm(char * buf) {
+  CELL *bc = (CELL *)buf;
+
+  return bc[0]+bc[1]*sizeof(CELL);
+}
+
 #define DEBUG_IMPORT 1
 
 #if DEBUG_IMPORT
diff --git a/H/Yapproto.h b/H/Yapproto.h
index 32f38f634..e1a4a1219 100644
--- a/H/Yapproto.h
+++ b/H/Yapproto.h
@@ -390,6 +390,7 @@ void	STD_PROTO(Yap_InitUserBacks,(void));
 Term	STD_PROTO(Yap_CopyTerm,(Term));
 int	STD_PROTO(Yap_Variant,(Term, Term));
 size_t	STD_PROTO(Yap_ExportTerm,(Term, char *, size_t, UInt));
+size_t	STD_PROTO(Yap_SizeOfExportedTerm,(char *));
 Term	STD_PROTO(Yap_ImportTerm,(char *));
 int	STD_PROTO(Yap_IsListTerm,(Term));
 Term	STD_PROTO(Yap_CopyTermNoShare,(Term));
diff --git a/include/YapInterface.h b/include/YapInterface.h
index 2db8a3e7a..371863aba 100644
--- a/include/YapInterface.h
+++ b/include/YapInterface.h
@@ -585,12 +585,14 @@ extern X_API YAP_Term PROTO(YAP_NewOpaqueObject,(YAP_opaque_tag_t, size_t));
 
 extern X_API void *PROTO(YAP_OpaqueObjectFromTerm,(YAP_Term));
 
-extern X_API int *PROTO(YAP_Argv,(char ***));
+extern X_API int  PROTO(YAP_Argv,(char ***));
 
 extern X_API YAP_tag_t PROTO(YAP_TagOfTerm,(YAP_Term));
 
 extern X_API size_t     PROTO(YAP_ExportTerm,(YAP_Term, char *, size_t));
 
+extern X_API size_t   PROTO(YAP_SizeOfExportedTerm,(char *));
+
 extern X_API YAP_Term     PROTO(YAP_ImportTerm,(char *));
 
 #define YAP_InitCPred(N,A,F)  YAP_UserCPredicate(N,F,A)
diff --git a/library/lammpi/hash.c b/library/lammpi/hash.c
index c47ba7f07..c557a5d2a 100644
--- a/library/lammpi/hash.c
+++ b/library/lammpi/hash.c
@@ -53,7 +53,7 @@ __ptr_t get_next_object(hashtable table,ulong key)
 }
 
 
-/* removes the element with key 'key' and returns the object stored on him */
+/* removes the element with key 'key' and returns the object stored on it */
 __ptr_t delete(hashtable table,ulong key)
 {
   __ptr_t obj;
diff --git a/library/lammpi/prologterms2c.c b/library/lammpi/prologterms2c.c
index 6be7685a7..86966efb1 100644
--- a/library/lammpi/prologterms2c.c
+++ b/library/lammpi/prologterms2c.c
@@ -99,9 +99,9 @@ expand_buffer(const size_t space ) {
 void
 change_buffer_size(const size_t newsize) {
 
-  if ( BUFFER_SIZE>=BLOCK_SIZE && BUFFER_SIZE>newsize)
+  if ( BUFFER_SIZE>=BLOCK_SIZE && BUFFER_SIZE>=newsize)
     return;
-  if(BUFFER_PTR) {
+  if (BUFFER_PTR) {
     free(BUFFER_PTR);
   }
   BUFFER_PTR = (char*)malloc(newsize);
@@ -185,17 +185,16 @@ term2string(char *const ptr, size_t *size, const YAP_Term t) {
 
   do {
     if (*size == 0) {
-      BUFFER_LEN = YAP_ExportTerm( t, BUFFER_PTR, BUFFER_SIZE );// canonical
+      *size = BUFFER_LEN = YAP_ExportTerm( t, BUFFER_PTR, BUFFER_SIZE );// canonical
       ret=BUFFER_PTR;
+      if (BUFFER_LEN == 0) {
+	expand_buffer(BLOCK_SIZE);
+      }
     } else {
-      BUFFER_LEN = YAP_ExportTerm( t, ptr, BUFFER_SIZE );// canonical
+      *size = YAP_ExportTerm( t, ptr, BUFFER_SIZE );// canonical
       ret=ptr;
     }
-    *size = BUFFER_LEN;
-    if (BUFFER_LEN == 0) {
-      expand_buffer(BLOCK_SIZE);
-    }
-  } while (BUFFER_LEN <= 0);
+  } while (*size <= 0);
   return ret;
 }
 /*
@@ -206,31 +205,10 @@ string2term(char *const ptr,const size_t *size) {
   YAP_Term t;
   struct buffer_ds b;
 
-  b.size=b.len=b.pos=0;
-  if (BUFFER_PTR!=ptr) {    //
-#ifdef DEBUG
-    write_msg(__FUNCTION__,__FILE__,__LINE__,"copy buffer string2term\n");
-#endif
-    COPY_BUFFER_DS(buffer,b); // keep a copy of buffer_ds
-    BUFFER_PTR=ptr;           // make the buffer use the buffer provided
-    BUFFER_LEN=*size;
-    BUFFER_SIZE=BUFFER_LEN;
-  } else {   // b aux. struct. not needed
-    b.ptr=NULL;
-  }
-  BUFFER_POS=0;
-  t = YAP_ImportTerm( BUFFER_PTR );
+  t = YAP_ImportTerm( ptr );
   if ( t==FALSE ) {
-    write_msg(__FUNCTION__,__FILE__,__LINE__,"FAILED string2term>>>>size:%d %d %s\n",BUFFER_SIZE,strlen(BUFFER_PTR),NULL);
+    write_msg(__FUNCTION__,__FILE__,__LINE__,"FAILED string2term>>>>size:%lx %d\n",t,*size);
     exit(1);
   }
-
-  if (b.ptr!=NULL)
-    COPY_BUFFER_DS(b,buffer);
-  
-#ifdef DEBUG
-  write_msg(__FUNCTION__,__FILE__,__LINE__,"ending: buffer(ptr=%p;size=%d;pos=%d;len=%d)\n",BUFFER_PTR,BUFFER_SIZE,BUFFER_POS,BUFFER_LEN);
-#endif
-
   return t;
 }                                                                                   
diff --git a/library/lammpi/prologterms2c.h b/library/lammpi/prologterms2c.h
index c6cd937e0..56a632a18 100644
--- a/library/lammpi/prologterms2c.h
+++ b/library/lammpi/prologterms2c.h
@@ -70,7 +70,7 @@ void write_msg(const char *fun,const char *file, int line,const char *format, ..
 #define BLOCK_SIZE 4*1024
 
 // deletes the buffer (all fields) but does not release the memory of the buffer.ptr
-#define DEL_BUFFER   {buffer.ptr=NULL;buffer.size=0;buffer.len=0;}
+#define DEL_BUFFER   {buffer.ptr=NULL;buffer.size=0;buffer.len=0;buffer.pos=0;}
 //  informs the prologterm2c module that the buffer is now used and should not be messed
 #define USED_BUFFER()  DEL_BUFFER
 // initialize buffer
diff --git a/library/lammpi/yap_mpi.c b/library/lammpi/yap_mpi.c
index 5b6eb90c5..7d6f79f67 100644
--- a/library/lammpi/yap_mpi.c
+++ b/library/lammpi/yap_mpi.c
@@ -81,6 +81,8 @@ extern int GLOBAL_argc;
 static hashtable requests=NULL;
 static hashtable broadcasts=NULL;
 
+void init_mpi(void);
+
 /********************************************************************
  * Time accounting
  ********************************************************************/
@@ -116,8 +118,6 @@ static struct timeval _tstart, _tend;
 #include <sys/resource.h>
 #include <unistd.h>
 
-void init_mpi(void);
-
 void tstart(void) {
   struct rusage r;
   getrusage(RUSAGE_SELF,&r);
@@ -407,12 +407,13 @@ mpi_isend(void) {
 #ifdef DEBUG
   write_msg(__FUNCTION__,__FILE__,__LINE__,"%s(%s,%u, MPI_CHAR,%d,%d)\n",__FUNCTION__,str,len,dest,tag);
 #endif
+  USED_BUFFER(); //  informs the prologterm2c module that the buffer is now used and should not be messed
   // We must associate the string to each handle
   new_request(handle,str);
-  USED_BUFFER(); //  informs the prologterm2c module that the buffer is now used and should not be messed
   PAUSE_TIMER();
   RETURN(YAP_Unify(YAP_ARG4,YAP_MkIntTerm(HANDLE2INT(handle))));// it should always succeed
 }
+
 /*
  * Blocking communication function. The message is sent immediatly.
  * mpi_send(+Data, +Destination, +Tag).
@@ -454,7 +455,7 @@ static int
 mpi_recv(void) {
   YAP_Term t1 = YAP_Deref(YAP_ARG1), 
     t2 = YAP_Deref(YAP_ARG2), 
-    t3 = YAP_Deref(YAP_ARG3),
+    t3 = YAP_Deref(YAP_ARG3), 
     t4;
   int tag, orig;
   int len=0;
@@ -490,7 +491,7 @@ mpi_recv(void) {
     RETURN(FALSE);
   }
   //realloc memory buffer
-  change_buffer_size(len+1);
+  change_buffer_size((size_t)(len+1));
   BUFFER_LEN=len; 
   // Already know the source from MPI_Probe()
   if( orig == MPI_ANY_SOURCE ) {
@@ -523,8 +524,9 @@ mpi_recv(void) {
   MSG_RECV(BUFFER_LEN);
   t4=string2term(BUFFER_PTR,&BUFFER_LEN);
   PAUSE_TIMER();
-  RETURN(YAP_Unify(t3,t4));
+  RETURN(YAP_Unify(YAP_ARG3,t4));
 }
+
 /*
  * Implements a non-blocking receive operation. 
  * mpi_irecv(?Source,?Tag,-Handle).
@@ -535,8 +537,6 @@ mpi_irecv(void) {
     t2 = YAP_Deref(YAP_ARG2), 
     t3 = YAP_Deref(YAP_ARG3);
   int tag, orig;
-  int len=0;
-  MPI_Status status;
   MPI_Request *handle=(MPI_Request*)malloc(sizeof(MPI_Request));
 
   // The third argument (data) must be unbound
@@ -558,34 +558,8 @@ mpi_irecv(void) {
   else  tag  = YAP_IntOfTerm( t2 );
 
   CONT_TIMER();
-
-  // probe for the size of the term 
-  if( MPI_CALL(MPI_Probe( orig, tag, MPI_COMM_WORLD, &status )) != MPI_SUCCESS ){
-    PAUSE_TIMER();
-    RETURN(FALSE);
-  }
-  //
-  MPI_CALL(MPI_Get_count( &status, MPI_CHAR, &len ));
-  change_buffer_size(len+1);  
-  BUFFER_LEN=len; 
-  // Already know the source from MPI_Probe()
-  if( orig == MPI_ANY_SOURCE ) {
-    orig = status.MPI_SOURCE;
-    if ( YAP_Unify(t1, YAP_MkIntTerm(orig))!=TRUE ) {
-      PAUSE_TIMER();
-      RETURN(FALSE);
-    }
-  }
-  // Already know the tag from MPI_Probe()
-  if( tag == MPI_ANY_TAG ) {
-    tag = status.MPI_TAG;
-    if (YAP_Unify(t2, YAP_MkIntTerm(status.MPI_TAG))!=TRUE) {
-      PAUSE_TIMER();
-      RETURN(FALSE);
-    }
-  }
-  
-  if(  MPI_CALL(MPI_Irecv( BUFFER_PTR, BUFFER_LEN, MPI_CHAR, orig, tag,
+  RESET_BUFFER;
+  if(  MPI_CALL(MPI_Irecv( BUFFER_PTR, BLOCK_SIZE, MPI_CHAR, orig, tag,
 		  MPI_COMM_WORLD, handle )) != MPI_SUCCESS ) {
     PAUSE_TIMER();
     RETURN(FALSE);
@@ -595,6 +569,7 @@ mpi_irecv(void) {
   PAUSE_TIMER();
   RETURN(YAP_Unify(t3,YAP_MkIntTerm(HANDLE2INT(handle))));
 }
+
 /*
  *  Completes a non-blocking operation. IF the operation was a send, the
  * function waits until the message is buffered or sent by the runtime
@@ -625,6 +600,7 @@ mpi_wait(void) {
   PAUSE_TIMER();
   RETURN(YAP_Unify(t2,YAP_MkIntTerm(status.MPI_ERROR)));
 }
+
 /*
  *  Provides information regarding a handle, ie. if a communication operation has been completed.
  * If the operation has been completed the predicate succeeds with the completion status,
@@ -656,6 +632,7 @@ mpi_test(void) {
   PAUSE_TIMER();
   RETURN(YAP_Unify(t2,YAP_MkIntTerm(status.MPI_ERROR)));
 }
+
 /*
  *  Completes a non-blocking operation. IF the operation was a send, the
  * function waits until the message is buffered or sent by the runtime
@@ -666,13 +643,12 @@ mpi_test(void) {
  */
 static int 
 mpi_wait_recv(void) {
-  YAP_Term t1 = YAP_Deref(YAP_ARG1), // Handle
-    t2 = YAP_Deref(YAP_ARG2), // Status
-    t3 = YAP_Deref(YAP_ARG3); // data
+  YAP_Term t1 = YAP_Deref(YAP_ARG1); // data
   MPI_Status status;
   MPI_Request *handle;
   char *s;
   int len,ret;
+  YAP_Term out;
 
   // The first argument (handle) must be an integer
   if(!YAP_IsIntTerm(t1)) {
@@ -681,19 +657,22 @@ mpi_wait_recv(void) {
   CONT_TIMER();
 
   handle=INT2HANDLE(YAP_IntOfTerm(t1));
+  s=(char*)get_request(handle);
   // wait for communication completion
   if( MPI_CALL(MPI_Wait( handle , &status )) != MPI_SUCCESS) {
     PAUSE_TIMER();
     RETURN(FALSE);
   }
-  s=(char*)get_request(handle);
-  len=strlen(s);
-  ret=YAP_Unify(t3,string2term(s,(size_t*)&len));
+  len=YAP_SizeOfExportedTerm(s);
+  // make sure we only fetch ARG3 after constructing the term
+  out = string2term(s,(size_t*)&len);
   MSG_RECV(len);
   free_request(handle);
   PAUSE_TIMER();
-  RETURN(ret & YAP_Unify(t2,YAP_MkIntTerm(status.MPI_ERROR)));
+  ret=YAP_Unify(YAP_ARG3,out);
+  RETURN(ret & YAP_Unify(YAP_ARG2,YAP_MkIntTerm(status.MPI_ERROR)));
 }
+
 /*
  * Provides information regarding a handle, ie. if a communication operation has been completed.
  * If the operation has been completed the predicate succeeds with the completion status,
@@ -703,14 +682,13 @@ mpi_wait_recv(void) {
  */
 static int 
 mpi_test_recv(void) {
-  YAP_Term t1 = YAP_Deref(YAP_ARG1), // Handle
-    t2 = YAP_Deref(YAP_ARG2), // Status
-    t3 = YAP_Deref(YAP_ARG3); // data
+  YAP_Term t1 = YAP_Deref(YAP_ARG1); // data
 
   MPI_Status status;
   MPI_Request *handle;
   int flag,len,ret;
   char *s;
+  YAP_Term out;
 
   // The first argument (handle) must be an integer
   if(!YAP_IsIntTerm(t1)) {
@@ -726,11 +704,14 @@ mpi_test_recv(void) {
   }
   s=(char*)get_request(handle);
   len=strlen(s);
-  ret=YAP_Unify(t3,string2term(s,(size_t*)&len));
+  out = string2term(s,(size_t*)&len);
+  // make sure we only fetch ARG3 after constructing the term
+  ret=YAP_Unify(YAP_ARG3,out);
   free_request(handle);
   PAUSE_TIMER();
-  RETURN(ret & YAP_Unify(t2,YAP_MkIntTerm(status.MPI_ERROR)));
+  RETURN(ret & YAP_Unify(YAP_ARG2,YAP_MkIntTerm(status.MPI_ERROR)));
 }
+
 /*
  * Collective communication function that performs a barrier synchronization among all processes.
  * mpi_barrier