Typo fixes and minor comment updates

opencl_fdtd/kernels/update_e.cl

@@ -4,7 +4,7 @@
  *  Template parameters:
  *   common_header: Rendered contents of common.cl
  *   pmls: [{'axis': 'x', 'polarity': 'n', 'thickness': 8}, ...] list of pml dicts containing
-        axes, polarities, and thicknesses.
+ *      axes, polarities, and thicknesses.
  *
  *  OpenCL args:
  *   E, H, dt, eps, [p{01}e{np}, Psi_{xyz}{np}_E]
@@ -20,7 +20,7 @@ __global ftype *epsz = eps + ZZ;
 
 
 /*
- *   Precalclate derivatives
+ *   Precalculate derivatives
  */
 ftype dHxy = Hx[i] - Hx[i + my];
 ftype dHxz = Hx[i] - Hx[i + mz];

opencl_fdtd/kernels/update_h.cl

@@ -5,7 +5,7 @@
  *  Template parameters:
  *   common_header: Rendered contents of common.cl
  *   pmls: [{'axis': 'x', 'polarity': 'n', 'thickness': 8}, ...] list of pml dicts containing
-        axes, polarities, and thicknesses.
+ *      axes, polarities, and thicknesses.
  *   do_poynting: Whether to precalculate poynting vector components (boolean)
  *
  *  OpenCL args:

opencl_fdtd/simulation.py

@@ -56,11 +56,11 @@ class Simulation(object):
      event0 and event1 to occur (i.e. previous operations to finish) before starting execution.
      event2 can then be used to prepare further operations to be run after update_H.
     """
-    E = None    # type: List[pyopencl.array.Array]
-    H = None    # type: List[pyopencl.array.Array]
-    S = None    # type: List[pyopencl.array.Array]
-    eps = None  # type: List[pyopencl.array.Array]
-    dt = None   # type: float
+    E = None            # type: pyopencl.array.Array
+    H = None            # type: pyopencl.array.Array
+    S = None            # type: pyopencl.array.Array
+    eps = None          # type: pyopencl.array.Array
+    dt = None           # type: float
 
     arg_type = None     # type: numpy.float32 or numpy.float64