diff --git a/opencl_fdfd/kernels/common.cl b/opencl_fdfd/kernels/common.cl
index 682152e..50adff9 100644
--- a/opencl_fdfd/kernels/common.cl
+++ b/opencl_fdfd/kernels/common.cl
@@ -4,17 +4,25 @@
  *  shape       list of 3 ints specifying shape of fields
  */
 
+/*
+ * Field size info
+ */
 // Field sizes
 const int sx = {{shape[0]}};
 const int sy = {{shape[1]}};
 const int sz = {{shape[2]}};
+const size_t field_size = sx * sy * sz;
 
 //Since we use i to index into Ex[], Ey[], ... rather than E[], do nothing if
 // i is outside the bounds of Ex[].
-if (i >= sx * sy * sz) {
+if (i >= field_size) {
     PYOPENCL_ELWISE_CONTINUE;
 }
 
+
+/*
+ * Array indexing
+ */
 // Given a linear index i and shape (sx, sy, sz), defines x, y, and z
 //  as the 3D indices of the current element (i).
 // (ie, converts linear index [i] to field indices (x, y, z)
@@ -28,11 +36,15 @@ const int dix = sz * sy;
 const int diy = sz;
 const int diz = 1;
 
+
+/*
+ * Pointer math
+ */
 //Pointer offsets into the components of a linearized vector-field
 // (eg. Hx = H + XX, where H and Hx are pointers)
 const int XX = 0;
-const int YY = sx * sy * sz;
-const int ZZ = sx * sy * sz * 2;
+const int YY = field_size;
+const int ZZ = field_size * 2;
 
 //Define pointers to vector components of each field (eg. Hx = H + XX)
 __global ctype *Ex = E + XX;
@@ -42,3 +54,26 @@ __global ctype *Ez = E + ZZ;
 __global ctype *Hx = H + XX;
 __global ctype *Hy = H + YY;
 __global ctype *Hz = H + ZZ;
+
+
+/*
+ * Implement periodic boundary conditions
+ *
+ * mx ([m]inus [x]) gives the index offset of the adjacent cell in the minus-x direction.
+ * In the event that we start at x == 0, we actually want to wrap around and grab the cell
+ * x_{-1} == (sx - 1) instead, ie. mx = (sx - 1) * dix .
+ *
+ * px ([p]lus [x]) gives the index offset of the adjacent cell in the plus-x direction.
+ * In the event that we start at x == (sx - 1), we actually want to wrap around and grab
+ * the cell x_{+1} == 0 instead, ie. px = -(sx - 1) * dix .
+ */
+{% for r in 'xyz' %}
+int m{{r}} = -di{{r}};
+int p{{r}} = +di{{r}};
+int wrap_{{r}} = (s{{r}} - 1) * di{{r}};
+if ( {{r}} == 0 ) {
+  m{{r}} = wrap_{{r}};
+} else if ( {{r}} == s{{r}} - 1 ) {
+  p{{r}} = -wrap_{{r}};
+}
+{% endfor %}
diff --git a/opencl_fdfd/kernels/e2h.cl b/opencl_fdfd/kernels/e2h.cl
index 8e2a076..c837e64 100644
--- a/opencl_fdfd/kernels/e2h.cl
+++ b/opencl_fdfd/kernels/e2h.cl
@@ -19,6 +19,8 @@
 
 {{common_cl}}
 
+////////////////////////////////////////////////////////////////////////////
+
 __global ctype *inv_mu_x = inv_mu + XX;
 __global ctype *inv_mu_y = inv_mu + YY;
 __global ctype *inv_mu_z = inv_mu + ZZ;
@@ -27,32 +29,6 @@ __global char *pmc_x = pmc + XX;
 __global char *pmc_y = pmc + YY;
 __global char *pmc_z = pmc + ZZ;
 
-/*
- * Implement periodic boundary conditions
- *
- * ipx gives the index of the adjacent cell in the plus-x direction ([i]ndex [p]lus [x]).
- * In the event that we start at x == (sx - 1), we actually want to wrap around and grab the cell
- * where x == 0 instead, ie. ipx = i - (sx - 1) * dix .
- */
-int ipx, ipy, ipz;
-if ( x == sx - 1 ) {
-  ipx = i - (sx - 1) * dix;
-} else {
-  ipx = i + dix;
-}
-
-if ( y == sy - 1 ) {
-  ipy = i - (sy - 1) * diy;
-} else {
-  ipy = i + diy;
-}
-
-if ( z == sz - 1 ) {
-  ipz = i - (sz - 1) * diz;
-} else {
-  ipz = i + diz;
-}
-
 
 //Update H components; set them to 0 if PMC is enabled at that location.
 //Mu division and PMC conditional are only included if {{mu}} and {{pmc}} are true
@@ -62,8 +38,8 @@ if (pmc_x[i] != 0) {
 } else
 {%- endif -%}
 {
-    ctype Dzy = mul(sub(Ez[ipy], Ez[i]), inv_dey[y]);
-    ctype Dyz = mul(sub(Ey[ipz], Ey[i]), inv_dez[z]);
+    ctype Dzy = mul(sub(Ez[i + py], Ez[i]), inv_dey[y]);
+    ctype Dyz = mul(sub(Ey[i + pz], Ey[i]), inv_dez[z]);
     ctype x_curl = sub(Dzy, Dyz);
 
     {%- if mu -%}
@@ -79,8 +55,8 @@ if (pmc_y[i] != 0) {
 } else
 {%- endif -%}
 {
-    ctype Dxz = mul(sub(Ex[ipz], Ex[i]), inv_dez[z]);
-    ctype Dzx = mul(sub(Ez[ipx], Ez[i]), inv_dex[x]);
+    ctype Dxz = mul(sub(Ex[i + pz], Ex[i]), inv_dez[z]);
+    ctype Dzx = mul(sub(Ez[i + px], Ez[i]), inv_dex[x]);
     ctype y_curl = sub(Dxz, Dzx);
 
     {%- if mu -%}
@@ -96,8 +72,8 @@ if (pmc_z[i] != 0) {
 } else
 {%- endif -%}
 {
-    ctype Dyx = mul(sub(Ey[ipx], Ey[i]), inv_dex[x]);
-    ctype Dxy = mul(sub(Ex[ipy], Ex[i]), inv_dey[y]);
+    ctype Dyx = mul(sub(Ey[i + px], Ey[i]), inv_dex[x]);
+    ctype Dxy = mul(sub(Ex[i + py], Ex[i]), inv_dey[y]);
     ctype z_curl = sub(Dyx, Dxy);
 
     {%- if mu -%}
diff --git a/opencl_fdfd/kernels/h2e.cl b/opencl_fdfd/kernels/h2e.cl
index d71a78c..f2fdadb 100644
--- a/opencl_fdfd/kernels/h2e.cl
+++ b/opencl_fdfd/kernels/h2e.cl
@@ -19,6 +19,7 @@
 
 {{common_cl}}
 
+////////////////////////////////////////////////////////////////////////////
 
 __global ctype *oeps_x = oeps + XX;
 __global ctype *oeps_y = oeps + YY;
@@ -33,41 +34,14 @@ __global ctype *Pl_y = Pl + YY;
 __global ctype *Pl_z = Pl + ZZ;
 
 
-/*
- * Implement periodic boundary conditions
- *
- * imx gives the index of the adjacent cell in the minus-x direction ([i]ndex [m]inus [x]).
- * In the event that we start at x == 0, we actually want to wrap around and grab the cell
- * where x == (sx - 1) instead, ie. imx = i + (sx - 1) * dix .
- */
-int imx, imy, imz;
-if ( x == 0 ) {
-  imx = i + (sx - 1) * dix;
-} else {
-  imx = i - dix;
-}
-
-if ( y == 0 ) {
-  imy = i + (sy - 1) * diy;
-} else {
-  imy = i - diy;
-}
-
-if ( z == 0 ) {
-  imz = i + (sz - 1) * diz;
-} else {
-  imz = i - diz;
-}
-
-
 //Update E components; set them to 0 if PEC is enabled there.
 {% if pec -%}
 if (pec_x[i] == 0)
 {%- endif -%}
 {
     ctype tEx = mul(Ex[i], oeps_x[i]);
-    ctype Dzy = mul(sub(Hz[i], Hz[imy]), inv_dhy[y]);
-    ctype Dyz = mul(sub(Hy[i], Hy[imz]), inv_dhz[z]);
+    ctype Dzy = mul(sub(Hz[i], Hz[i + my]), inv_dhy[y]);
+    ctype Dyz = mul(sub(Hy[i], Hy[i + mz]), inv_dhz[z]);
     tEx = add(tEx, sub(Dzy, Dyz));
     Ex[i] = mul(tEx, Pl_x[i]);
 }
@@ -77,8 +51,8 @@ if (pec_y[i] == 0)
 {%- endif -%}
 {
     ctype tEy = mul(Ey[i], oeps_y[i]);
-    ctype Dxz = mul(sub(Hx[i], Hx[imz]), inv_dhz[z]);
-    ctype Dzx = mul(sub(Hz[i], Hz[imx]), inv_dhx[x]);
+    ctype Dxz = mul(sub(Hx[i], Hx[i + mz]), inv_dhz[z]);
+    ctype Dzx = mul(sub(Hz[i], Hz[i + mx]), inv_dhx[x]);
     tEy = add(tEy, sub(Dxz, Dzx));
     Ey[i] = mul(tEy, Pl_y[i]);
 }
@@ -88,8 +62,8 @@ if (pec_z[i] == 0)
 {%- endif -%}
 {
     ctype tEz = mul(Ez[i], oeps_z[i]);
-    ctype Dyx = mul(sub(Hy[i], Hy[imx]), inv_dhx[x]);
-    ctype Dxy = mul(sub(Hx[i], Hx[imy]), inv_dhy[y]);
+    ctype Dyx = mul(sub(Hy[i], Hy[i + mx]), inv_dhx[x]);
+    ctype Dxy = mul(sub(Hx[i], Hx[i + my]), inv_dhy[y]);
     tEz = add(tEz, sub(Dyx, Dxy));
     Ez[i] = mul(tEz, Pl_z[i]);
 }
diff --git a/opencl_fdfd/main.py b/opencl_fdfd/main.py
index 6903556..3b79aa9 100644
--- a/opencl_fdfd/main.py
+++ b/opencl_fdfd/main.py
@@ -113,7 +113,7 @@ def cg_solver(omega: complex,
         Allocate GPU memory and load in data
     '''
     if context is None:
-        context = pyopencl.create_some_context(False)
+        context = pyopencl.create_some_context(interactive=True)
 
     queue = pyopencl.CommandQueue(context)