diff --git a/src/graph/graph_comm.f90 b/src/graph/graph_comm.f90
index d107df1d..67f9633a 100644
--- a/src/graph/graph_comm.f90
+++ b/src/graph/graph_comm.f90
@@ -35,7 +35,7 @@ subroutine monolis_com_get_comm_table(monolis, N, NP, nid)
     integer(kint), allocatable :: counts(:), outer_node_id_local(:), local_nid(:)
     integer(kint), allocatable :: outer_node_id_all(:), outer_dom_id_all(:), temp(:)
     integer(kint), allocatable :: displs(:), internal_node_id(:), is_neib(:), neib_id(:)
-    integer(kint), allocatable :: send_n_list(:), rbuf(:)
+    integer(kint), allocatable :: send_n_list(:)
     integer(kint), allocatable :: ws(:), wr(:)
     integer(kint), allocatable :: sta1(:,:)
     integer(kint), allocatable :: sta2(:,:)
@@ -170,7 +170,6 @@ subroutine monolis_com_get_comm_table(monolis, N, NP, nid)
     !> send の作成
     !> slave から master に個数を送信
     allocate(send_n_list(commsize), source = 0)
-    allocate(rbuf(commsize), source = 0)
 
     do i = 1, n_neib_recv
       id = recv_list(i)%domid
@@ -178,9 +177,8 @@ subroutine monolis_com_get_comm_table(monolis, N, NP, nid)
       send_n_list(id + 1) = in
     enddo
 
-    call mpi_alltoall(send_n_list, 1, MPI_INTEGER, &
-      rbuf, 1, MPI_INTEGER, monolis%COM%comm, ierr)
-    send_n_list = rbuf
+    call mpi_alltoall(MPI_IN_PLACE, 1, MPI_INTEGER, &
+      send_n_list, 1, MPI_INTEGER, monolis%COM%comm, ierr)
 
     !> send 個数の確保
     n_neib_send = 0
@@ -309,7 +307,7 @@ subroutine monolis_com_get_comm_table_analysis(N, NP, nid, &
     integer(kint), allocatable :: counts(:), outer_node_id_local(:), local_nid(:)
     integer(kint), allocatable :: outer_node_id_all(:), outer_dom_id_all(:)
     integer(kint), allocatable :: displs(:), internal_node_id(:), is_neib(:), neib_id(:)
-    integer(kint), allocatable :: send_n_list(:), rbuf(:)
+    integer(kint), allocatable :: send_n_list(:)
 
     myrank = monolis_global_myrank()
     commsize = monolis_global_commsize()
@@ -417,7 +415,6 @@ subroutine monolis_com_get_comm_table_analysis(N, NP, nid, &
     !> send の作成
     !> slave から master に個数を送信
     allocate(send_n_list(commsize), source = 0)
-    allocate(rbuf(commsize), source = 0)
 
     do i = 1, n_neib_recv
       id = recv_list(i)%domid
@@ -425,9 +422,8 @@ subroutine monolis_com_get_comm_table_analysis(N, NP, nid, &
       send_n_list(id + 1) = in
     enddo
 
-    call mpi_alltoall(send_n_list, 1, MPI_INTEGER, &
-      rbuf, 1, MPI_INTEGER, comm, ierr)
-    send_n_list = rbuf
+    call mpi_alltoall(MPI_IN_PLACE, 1, MPI_INTEGER, &
+      send_n_list, 1, MPI_INTEGER, comm, ierr)
 
     !> send 個数の確保
     n_neib_send = 0
@@ -508,7 +504,7 @@ subroutine monolis_com_get_comm_table_set(monolis, N, NP, nid)
     integer(kint), allocatable :: counts(:), outer_node_id_local(:), local_nid(:)
     integer(kint), allocatable :: outer_node_id_all(:), outer_dom_id_all(:), temp(:)
     integer(kint), allocatable :: displs(:), internal_node_id(:), is_neib(:), neib_id(:)
-    integer(kint), allocatable :: send_n_list(:), rbuf(:)
+    integer(kint), allocatable :: send_n_list(:)
     integer(kint), allocatable :: ws(:), wr(:)
     integer(kint), allocatable :: sta1(:,:)
     integer(kint), allocatable :: sta2(:,:)
@@ -643,7 +639,6 @@ subroutine monolis_com_get_comm_table_set(monolis, N, NP, nid)
     !> send の作成
     !> slave から master に個数を送信
     allocate(send_n_list(commsize), source = 0)
-    allocate(rbuf(commsize), source = 0)
 
     do i = 1, n_neib_recv
       id = recv_list(i)%domid
@@ -651,9 +646,8 @@ subroutine monolis_com_get_comm_table_set(monolis, N, NP, nid)
       send_n_list(id + 1) = in
     enddo
 
-    call mpi_alltoall(send_n_list, 1, MPI_INTEGER, &
+    call mpi_alltoall(MPI_IN_PLACE, 1, MPI_INTEGER, &
       send_n_list, 1, MPI_INTEGER, monolis%COM%comm, ierr)
-    send_n_list = rbuf
 
     !> send 個数の確保
     n_neib_send = 0