diff --git a/code/code_gen/post.py b/code/code_gen/post.py
index ecb271f..526757c 100644
--- a/code/code_gen/post.py
+++ b/code/code_gen/post.py
@@ -235,41 +235,50 @@ real*8, allocatable, dimension(:,:,:) :: {field_name}_export_array
 
     fmt_init='''
 ! init
-! call MPI_INFO_CREATE({field_name}_info, mpi_err)
-! call MPI_FILE_OPEN(MPI_COMM_TASK,{field_name}_fname,MPI_MODE_WRONLY+MPI_MODE_CREATE,{field_name}_info,{field_name}_fh,mpi_err)
-! allocate({field_name}_export_array({1}), stat=ierr) ; {field_name}_export_array = 0.
+call MPI_INFO_CREATE({field_name}_info, mpi_err)
+call MPI_FILE_OPEN(MPI_COMM_TASK,'{field_name}-export.dat',MPI_MODE_WRONLY+MPI_MODE_CREATE,{field_name}_info,{field_name}_fh,mpi_err)
+allocate({field_name}_export_array({xs}:{xe},{ys}:{ye},{zs}:{ze}), stat=ierr) ; {field_name}_export_array = 0.
 '''
 
     fmt_final='''
 ! finalize
-! call MPI_FILE_CLOSE({field_name}_fh, mpi_err)
-! call MPI_INFO_FREE({field_name}_info, mpi_err)
-! deallocate({field_name}_export_array)
+call MPI_FILE_CLOSE({field_name}_fh, mpi_err)
+call MPI_INFO_FREE({field_name}_info, mpi_err)
+deallocate({field_name}_export_array)
 '''
 
     fmt_calc='''
 ! copy to array for export
 ! do k = 1, nzp
 ! do j = 1, nyp
-! do i = {}, {}
-! {}(i,j,k) = {}(i,j,k)
+! do i = {x_start}, {x_end}
+! {field_name}_export_array(i,j,k) = {work_array}(i,j,k)
 ! end do
 ! end do
 ! end do
 
-! after calculate
-! count = {x1-x0+1} * ny * nz
-! offset = time_count * count
-! call MPI_FILE_WRITE_AT({field_name}_fh, offset, {field_name}_export_buffer, count, MPI_REAL8, mpi_status, mpi_err)
+! write to file
+! count = ({xe} - {xs} + 1) * ({ye} - {ys} + 1) * ({ze} - {zs} + 1)
+! offset = {itime} * count
+! call MPI_FILE_WRITE_AT({field_name}_fh, offset, {field_name}_export_array, count, MPI_REAL8, mpi_status, mpi_err)
 '''
 
     def __init__ (self, name, attr, parent):
         self.name = name
         self.attr = attr
         self.parent = parent
-        self.x0 = attr["x0"]
-        self.x1 = attr["x1"]
-        self.xslice = "{}:{},ny,nz".format(self.x0, self.x1)
+        # self.xslice = "{}:{},ny,nz".format(self.x0, self.x1)
+
+        self.params = dict(attr)
+
+        self.params.setdefault("xs", 1)
+        self.params.setdefault("xe", "nxp")
+        self.params.setdefault("ys", 1)
+        self.params.setdefault("ye", "nyp")
+        self.params.setdefault("zs", 1)
+        self.params.setdefault("ze", "nzp")
+
+        self.params.setdefault("field_name", self.name)
 
 
     def code (self):
@@ -277,13 +286,13 @@ real*8, allocatable, dimension(:,:,:) :: {field_name}_export_array
         return FieldExporter.fmt_calc # real_array_loop.format((self.array, rhs), self.comment)
 
     def code_decl (self):
-        return FieldExporter.fmt_decl.format(field_name=self.name)
+        return FieldExporter.fmt_decl.format(**self.params)
 
     def code_alloc (self):
-        return FieldExporter.fmt_init # real_array_alloc.format(self.name, self.shape)
+        return FieldExporter.fmt_init.format(**self.params)
 
     def code_free (self):
-        return FieldExporter.fmt_final # real_array_free.format(self.name)
+        return FieldExporter.fmt_final.format(**self.params)
 
 
 
diff --git a/code/code_gen/terms.input b/code/code_gen/terms.input
index 4daf6ee..277294e 100644
--- a/code/code_gen/terms.input
+++ b/code/code_gen/terms.input
@@ -10,6 +10,6 @@ nx = - ddx(c) / fsd
 ny = - ddy(c) / fsd
 nz = - ddz(c) / fsd
 
-divn (export=true, x0=128, x1=320) = ddx(nx) + ddy(ny) + ddz(nz)
+divn (export=true, xs=176, xe=400) = ddx(nx) + ddy(ny) + ddz(nz)
 
 avg { c, fsd, divn }
diff --git a/code/m_terms.f90 b/code/m_terms.f90
index 9fdb607..05a6c8d 100644
--- a/code/m_terms.f90
+++ b/code/m_terms.f90
@@ -41,9 +41,9 @@ allocate(avg_fsd(nxp), stat=ierr) ; avg_fsd = 0.
 allocate(avg_divn(nxp), stat=ierr) ; avg_divn = 0.
 
 ! init
-! call MPI_INFO_CREATE({field_name}_info, mpi_err)
-! call MPI_FILE_OPEN(MPI_COMM_TASK,{field_name}_fname,MPI_MODE_WRONLY+MPI_MODE_CREATE,{field_name}_info,{field_name}_fh,mpi_err)
-! allocate({field_name}_export_array({1}), stat=ierr) ; {field_name}_export_array = 0.
+call MPI_INFO_CREATE(divn_info, mpi_err)
+call MPI_FILE_OPEN(MPI_COMM_TASK,'divn-export.dat',MPI_MODE_WRONLY+MPI_MODE_CREATE,divn_info,divn_fh,mpi_err)
+allocate(divn_export_array(176:400,1:nyp,1:nzp), stat=ierr) ; divn_export_array = 0.
 
 allocate(xyzbuffer0(nxp,nyp,nzp), stat=ierr) ; xyzbuffer0 = 0.
 allocate(xyzbuffer1(nxp,nyp,nzp), stat=ierr) ; xyzbuffer1 = 0.
@@ -61,9 +61,9 @@ deallocate(avg_fsd)
 deallocate(avg_divn)
 
 ! finalize
-! call MPI_FILE_CLOSE({field_name}_fh, mpi_err)
-! call MPI_INFO_FREE({field_name}_info, mpi_err)
-! deallocate({field_name}_export_array)
+call MPI_FILE_CLOSE(divn_fh, mpi_err)
+call MPI_INFO_FREE(divn_info, mpi_err)
+deallocate(divn_export_array)
 
 deallocate(xyzbuffer0)
 deallocate(xyzbuffer1)
@@ -165,16 +165,16 @@ end do
 ! copy to array for export
 ! do k = 1, nzp
 ! do j = 1, nyp
-! do i = {}, {}
-! {}(i,j,k) = {}(i,j,k)
+! do i = {x_start}, {x_end}
+! {field_name}_export_array(i,j,k) = {work_array}(i,j,k)
 ! end do
 ! end do
 ! end do
 
-! after calculate
-! count = {x1-x0+1} * ny * nz
-! offset = time_count * count
-! call MPI_FILE_WRITE_AT({field_name}_fh, offset, {field_name}_export_buffer, count, MPI_REAL8, mpi_status, mpi_err)
+! write to file
+! count = ({xe} - {xs} + 1) * ({ye} - {ys} + 1) * ({ze} - {zs} + 1)
+! offset = {itime} * count
+! call MPI_FILE_WRITE_AT({field_name}_fh, offset, {field_name}_export_array, count, MPI_REAL8, mpi_status, mpi_err)
 
 
 do k = 1, nzp