diff --git a/src/Init/Init_FFTW.cpp b/src/Init/Init_FFTW.cpp
index a2115f0be..a9320d163 100644
--- a/src/Init/Init_FFTW.cpp
+++ b/src/Init/Init_FFTW.cpp
@@ -27,7 +27,15 @@ gramfe_fftw::complex_plan_1d FFTW_Plan_ExtPsi, FFTW_Plan_ExtPsi_Inv;   // ExtPsi
 // Return      :  length of array that is large enough to store FFT input and output
 //-------------------------------------------------------------------------------------------------------
 size_t ComputePaddedTotalSize(int* size) {
+#  ifdef SERIAL
    return 2*((size_t)size[0]/2+1)*size[1]*size[2];
+#  else
+   mpi_index_int local_nz, local_z_start, local_ny_after_transpose, local_y_start_after_transpose;
+
+   return (size_t)fftw_mpi_local_size_3d_transposed(size[2], size[1], 2*(size[0]/2+1),
+                                                    MPI_COMM_WORLD, &local_nz, &local_z_start, &local_ny_after_transpose,
+                                                    &local_y_start_after_transpose);
+#  endif //#if SERIAL
 } // FUNCTION : ComputePaddedTotalSize
 
 
@@ -41,7 +49,15 @@ size_t ComputePaddedTotalSize(int* size) {
 // Return      :  length of array that is large enough to store FFT input and output
 //-------------------------------------------------------------------------------------------------------
 size_t ComputeTotalSize(int* size) {
+#  ifdef SERIAL
    return (size_t)size[0]*size[1]*size[2];
+#  else
+   mpi_index_int local_nz, local_z_start, local_ny_after_transpose, local_y_start_after_transpose;
+
+   return (size_t)fftw_mpi_local_size_3d_transposed(size[2], size[1], size[0],
+                                                    MPI_COMM_WORLD, &local_nz, &local_z_start, &local_ny_after_transpose,
+                                                    &local_y_start_after_transpose);
+#  endif
 } // FUNCTION : ComputeTotalSize
 
 
@@ -167,7 +183,7 @@ void Init_FFTW()
    RhoK = (real*) root_fftw::fft_malloc(ComputePaddedTotalSize(Gravity_FFT_Size) * sizeof(real));
 #  endif // # ifdef GRAVITY
 #  if ( MODEL == ELBDM )
-   PsiK = (real*) root_fftw::fft_malloc( ComputeTotalSize      ( Psi_FFT_Size     ) * sizeof(real) * 2 );  // 2 * real for size of complex number
+   PsiK = (real*) root_fftw::fft_malloc( ComputeTotalSize     ( Psi_FFT_Size   ) * sizeof(real) * 2 );  // 2 * real for size of complex number
 #  endif // # if ( MODEL == ELBDM )
 
 #  if ( WAVE_SCHEME == WAVE_GRAMFE )
@@ -337,7 +353,7 @@ void Patch2Slab( real *VarS, real *SendBuf_Var, real *RecvBuf_Var, long *SendBuf
    const int SSize[2]   = { ( InPlacePad ? 2*(FFT_Size[0]/2+1) : FFT_Size[0] ), FFT_Size[1] };     // padded slab size in the x and y directions
    const int PSSize     = PS1*PS1;                                // patch slice size
 // const int MemUnit    = amr->NPatchComma[0][1]*PS1/MPI_NRank;   // set arbitrarily
-   const int MemUnit    = amr->NPatchComma[0][1]*PS1;             // set arbitrarily
+   const int MemUnit    = amr->NPatchComma[0][1]/MPI_NRank;       // set arbitrarily
    const int AveNz      = FFT_Size[2]/MPI_NRank + ( ( FFT_Size[2]%MPI_NRank == 0 ) ? 0 : 1 );    // average slab thickness
    const int Scale0     = amr->scale[0];
 
@@ -363,6 +379,15 @@ void Patch2Slab( real *VarS, real *SendBuf_Var, real *RecvBuf_Var, long *SendBuf
       TempBuf_SIdx   [r] = (long*)malloc( MemSize[r]*sizeof(long)        );
       TempBuf_Var    [r] = (real*)malloc( MemSize[r]*sizeof(real)*PSSize );
       List_NSend_SIdx[r] = 0;
+
+      if ( List_PID[r] == NULL )
+          Aux_Error( ERROR_INFO, "List_PID[%d] is NULL on Rank %d !!\n", r, MPI_Rank );
+      if ( List_k[r] == NULL )
+          Aux_Error( ERROR_INFO, "List_k[%d] is NULL on Rank %d !!\n", r, MPI_Rank );
+      if ( TempBuf_SIdx[r] == NULL )
+          Aux_Error( ERROR_INFO, "TempBuf_SIdx[%d] is NULL on Rank %d !!\n", r, MPI_Rank );
+      if ( TempBuf_Var[r] == NULL )
+          Aux_Error( ERROR_INFO, "TempBuf_Var[%d] is NULL on Rank %d !!\n", r, MPI_Rank ); 
    }
 
 
@@ -441,6 +466,15 @@ void Patch2Slab( real *VarS, real *SendBuf_Var, real *RecvBuf_Var, long *SendBuf
                List_k      [TRank]  = (int* )realloc( List_k      [TRank], MemSize[TRank]*sizeof(int)         );
                TempBuf_SIdx[TRank]  = (long*)realloc( TempBuf_SIdx[TRank], MemSize[TRank]*sizeof(long)        );
                TempBuf_Var [TRank]  = (real*)realloc( TempBuf_Var [TRank], MemSize[TRank]*sizeof(real)*PSSize );
+      
+               if ( List_PID[TRank] == NULL )
+                  Aux_Error( ERROR_INFO, "List_PID[%d] is NULL on Rank %d !!\n", TRank, MPI_Rank );
+               if ( List_k[TRank] == NULL )
+                  Aux_Error( ERROR_INFO, "List_k[%d] is NULL on Rank %d !!\n", TRank, MPI_Rank );
+               if ( TempBuf_SIdx[TRank] == NULL )
+                  Aux_Error( ERROR_INFO, "TempBuf_SIdx[%d] is NULL on Rank %d !!\n", TRank, MPI_Rank );
+               if ( TempBuf_Var[TRank] == NULL )
+                  Aux_Error( ERROR_INFO, "TempBuf_Var[%d] is NULL on Rank %d !!\n", TRank, MPI_Rank );
             }
 
 //          record list