diff --git a/code/post.f90 b/code/post.f90
index 5395a4f..37fcda6 100644
--- a/code/post.f90
+++ b/code/post.f90
@@ -102,6 +102,7 @@
 
      SUBROUTINE main_lb
       INTEGER :: fread,i
+      LOGICAL :: received
 
       CALL READ_INTRO
 
@@ -132,7 +133,13 @@
 
                   countnum=countnum+1
 
-                  CALL MPI_RECV(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_status, mpi_err)
+                  CALL MPI_Irecv(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_request, mpi_err)
+                  do
+                      call MPI_Test(mpi_request, received, mpi_status, mpi_err)
+                      if (received) exit
+                      call SLEEP (1)
+                  end do
+
                   CALL MPI_SEND(fread, 1, MPI_INTEGER, id_to, tag, MPI_COMM_TASK, mpi_err)
 
               ENDIF
@@ -141,7 +148,13 @@
 
           end_of_dispatch1: DO i=1,numprocs-1
 
-              CALL MPI_RECV(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_status, mpi_err)
+              CALL MPI_Irecv (id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_request, mpi_err)
+              do
+                call MPI_Test(mpi_request, received, mpi_status, mpi_err)
+                if (received) exit
+                call SLEEP (1)
+              end do
+
               CALL MPI_SEND(-1,    1, MPI_INTEGER, id_to,          tag, MPI_COMM_TASK, mpi_err)
 
           ENDDO end_of_dispatch1
@@ -190,7 +203,13 @@
 
               ELSE
 
-                  CALL MPI_RECV(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_status, mpi_err)
+                  CALL MPI_Irecv(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_request, mpi_err)
+                  do
+                      call MPI_Test(mpi_request, received, mpi_status, mpi_err)
+                      if (received) exit
+                      call SLEEP (1)
+                  end do
+
                   CALL MPI_SEND(fread, 1, MPI_INTEGER, id_to,          tag, MPI_COMM_TASK, mpi_err)
 
               ENDIF
@@ -199,7 +218,13 @@
 
           end_of_dispatch2: DO i=1,numprocs-1
 
-              CALL MPI_RECV(id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_status, mpi_err)
+              CALL MPI_Irecv (id_to, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag, MPI_COMM_TASK, mpi_request, mpi_err)
+              do
+                call MPI_Test(mpi_request, received, mpi_status, mpi_err)
+                if (received) exit
+                call SLEEP (1)
+              end do
+
               CALL MPI_SEND(-1,    1, MPI_INTEGER, id_to,          tag, MPI_COMM_TASK, mpi_err)
 
           ENDDO end_of_dispatch2