diff --git a/code/m_calculate.f90 b/code/m_calculate.f90
index b1cf20e..d62ce53 100644
--- a/code/m_calculate.f90
+++ b/code/m_calculate.f90
@@ -16,7 +16,7 @@ module m_calculate
     real*8, allocatable, dimension(:,:,:) :: zsrc
     real*8, allocatable, dimension(:,:,:) :: zdst
 
-    integer, parameter :: nb = 16
+    integer, parameter :: nb = BLOCKSIZE
 
     private :: work, nb
     private :: xsrc, xdst, zsrc, zdst
@@ -128,17 +128,13 @@ contains
         do j = 1,nyp
 
         do k = 1,nzp
-        do i = 1,nxp
-        rsrc(i,k) = src(i,j,k)
-        end do
+        rsrc(:,k) = src(:,j,k)
         end do
 
         call dfp(nzp, hzp, rsrc, rdst, nxp, 3)
 
         do k = 1,nzp
-        do i = 1,nxp
-        dst(i,j,k) = rdst(i,k)
-        end do
+        dst(:,j,k) = rdst(:,k)
         end do
 
         end do
@@ -215,17 +211,13 @@ contains
         do j = 1,nyp
 
         do k = 1,nzp
-        do i = 1,nxp
-        rsrc(i,k) = src(i,j,k)
-        end do
+        rsrc(:,k) = src(:,j,k)
         end do
 
         call d2fp(nzp, hzp, rsrc, rdst, nxp, 3)
 
         do k = 1,nzp
-        do i = 1,nxp
-        dst(i,j,k) = rdst(i,k)
-        end do
+        dst(:,j,k) = rdst(:,k)
         end do
 
         end do
@@ -258,8 +250,8 @@ contains
             DO jj=1,n2,nb
              DO ii=1,n1,nb
 
-            DO j=jj,jj+nb-1
-             DO i=ii,ii+nb-1
+            DO j=jj,min(jj+nb-1,n2)
+             DO i=ii,min(ii+nb-1,n1)
                a(i,j) = b(j,i)
              ENDDO
             ENDDO
diff --git a/code/makefile b/code/makefile
index 596aab9..93aa037 100644
--- a/code/makefile
+++ b/code/makefile
@@ -2,7 +2,11 @@
 #Neuman flags
 #flags = -O3 -r8 -i8 -openmp -msse3 -axSSSE3 -m64 -fPIC -i_dynamic
 #Cluster_2(16.161) flags 
-flags = -Wall -O3 -ffree-line-length-0 -fdefault-integer-8 -fdefault-double-8 -fdefault-real-8 -march=native
+
+
+BLOCKSIZE?=16
+
+flags = -cpp -DBLOCKSIZE=$(BLOCKSIZE) -Wall -O3 -ffree-line-length-0 -fdefault-integer-8 -fdefault-double-8 -fdefault-real-8 -march=native
 
 ifdef CHECK
 flags += -fcheck=all