diff --git a/src/gravity.F90 b/src/gravity.F90
index 200fb64..82824ec 100644
--- a/src/gravity.F90
+++ b/src/gravity.F90
@@ -216,11 +216,11 @@ module gravity
 !
 !     t, dt   - time and the time increment;
 !     x, y, z - rectangular coordinates;
-!     gacc    - vector of the gravitational acceleration;
+!     acc     - vector of the gravitational acceleration;
 !
 !===============================================================================
 !
-  subroutine gacc_none(t, dt, x, y, z, gacc)
+  subroutine gacc_none(t, dt, x, y, z, acc)
 
 ! local variables are not implicit by default
 !
@@ -230,7 +230,7 @@ module gravity
 !
     real(kind=8)              , intent(in)  :: t, dt
     real(kind=8)              , intent(in)  :: x, y, z
-    real(kind=8), dimension(3), intent(out) :: gacc
+    real(kind=8), dimension(3), intent(out) :: acc
 !
 !-------------------------------------------------------------------------------
 !
@@ -240,6 +240,10 @@ module gravity
     call start_timer(imc)
 #endif /* PROFILE */
 
+! reset gravitational acceleration
+!
+    acc(:) = 0.0d+00
+
 #ifdef PROFILE
 ! stop accounting time for the gravitational acceleration calculation
 !
diff --git a/src/io.F90 b/src/io.F90
index 1381bb2..44e9df0 100644
--- a/src/io.F90
+++ b/src/io.F90
@@ -33,9 +33,7 @@ module io
 ! import external subroutines
 !
   use blocks, only : pointer_meta
-#ifdef PROFILE
   use timers, only : set_timer, start_timer, stop_timer
-#endif /* PROFILE */
 
 ! module variables are not implicit by default
 !
@@ -89,9 +87,10 @@ module io
 #endif /* HDF5 */
   end interface
 
-#ifdef PROFILE
 ! timer indices
 !
+  integer            , save :: iio
+#ifdef PROFILE
   integer            , save :: ioi, iow, ios
 #endif /* PROFILE */
 
@@ -204,9 +203,10 @@ module io
 !
 !-------------------------------------------------------------------------------
 !
-#ifdef PROFILE
 ! set timer descriptions
 !
+    call set_timer('SNAPSHOTS I/O'        , iio)
+#ifdef PROFILE
     call set_timer('io:: initialization'  , ioi)
     call set_timer('io:: snapshot writing', iow)
     call set_timer('io:: snapshot reading', ios)
@@ -360,12 +360,24 @@ module io
     call start_timer(ios)
 #endif /* PROFILE */
 
+! reset the return flag
+!
+    iret = 0
+
+! start accounting time for I/O
+!
+    call start_timer(iio)
+
 #ifdef HDF5
 ! read HDF5 restart file and rebuild the meta and data block structures
 !
     call read_restart_snapshot_h5(iret)
 #endif /* HDF5 */
 
+! stop accounting time for I/O
+!
+    call stop_timer(iio)
+
 ! calculate the shift of the snapshot counter, and the next snapshot time
 !
     ishift = int(time / hsnap) - isnap + 1
@@ -411,6 +423,10 @@ module io
 !
 !-------------------------------------------------------------------------------
 !
+! reset the return flag
+!
+    iret = 0
+
 ! check if conditions for storing the restart snapshot have been met
 !
     if (hrest < 5.0d-02 .or. thrs < irest * hrest) return
@@ -421,12 +437,20 @@ module io
     call start_timer(iow)
 #endif /* PROFILE */
 
+! start accounting time for I/O
+!
+    call start_timer(iio)
+
 #ifdef HDF5
 ! store restart file
 !
     call write_restart_snapshot_h5(nrun, iret)
 #endif /* HDF5 */
 
+! stop accounting time for I/O
+!
+    call stop_timer(iio)
+
 ! increase the restart snapshot counter
 !
     irest = irest + 1
@@ -476,6 +500,10 @@ module io
     call start_timer(iow)
 #endif /* PROFILE */
 
+! start accounting time for I/O
+!
+    call start_timer(iio)
+
 #ifdef HDF5
 ! store variable snapshot file
 !
@@ -486,6 +514,10 @@ module io
     end if
 #endif /* HDF5 */
 
+! stop accounting time for I/O
+!
+    call stop_timer(iio)
+
 ! increase the snapshot counter and calculate the next snapshot time
 !
     isnap = isnap + 1
diff --git a/src/user_problem.F90 b/src/user_problem.F90
index 8a2332e..dab5585 100644
--- a/src/user_problem.F90
+++ b/src/user_problem.F90
@@ -831,6 +831,10 @@ module user_problem
     call start_timer(img)
 #endif /* PROFILE */
 
+! reset gravitational acceleration
+!
+    acc(:) = 0.0d+00
+
 #ifdef PROFILE
 ! stop accounting time for the gravitational acceleration calculation
 !