Add function to estimate number of cells as power of 2 (#36)

- Add small function to get closest power of 2
- Update live notebook

live/01-forward-dc-resisitivity-2d.ipynb

@@ -200,18 +200,31 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# Number of base cells along x and y\n",
-    "nbcx = 2 ** int(np.round(np.log(dom_width_x / dh) / np.log(2.0)))\n",
-    "nbcy = 2 ** int(np.round(np.log(dom_width_y / dh) / np.log(2.0)))\n",
+    "def get_closest_power_of_2(x):\n",
+    "    \"\"\"\n",
+    "    Get the closest power of 2 to the given x\n",
+    "    \"\"\"\n",
+    "    return 2 ** int(np.round(np.log(x) / np.log(2.0)))\n",
     "\n",
+    "# Number of base cells along x and y\n",
+    "n_base_cells_x = get_closest_power_of_2(n_cells_x)\n",
+    "n_base_cells_y = get_closest_power_of_2(n_cells_y)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
     "# Define the base mesh with top at z = 0 m.\n",
-    "hx = [(dh, nbcx)]\n",
-    "hy = [(dh, nbcy)]\n",
+    "hx = [(dh, n_base_cells_x)]\n",
+    "hy = [(dh, n_base_cells_y)]\n",
     "mesh = TreeMesh([hx, hy], origin=\"CN\")\n",
     "\n",
     "# Shift top to maximum topography and center of survey line\n",
-    "y_topo_max = np.max(topo_2d[:, -1])\n",
-    "mesh.origin = mesh.origin + np.r_[0, y_topo_max]"
+    "x_center = survey.unique_electrode_locations[:, 0].mean()\n",
+    "mesh.origin = mesh.origin + np.r_[x_center, y_topo.max()]"
    ]
   },
   {