diff --git a/requirements.txt b/requirements.txt
index 44c9804..62d66ea 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,7 @@
 build
 debugpy
 ipython
+jax
 jupytext
 matplotlib-backend-kitty
 numpy
diff --git a/src/root.py b/src/root.py
new file mode 100644
index 0000000..204a5c0
--- /dev/null
+++ b/src/root.py
@@ -0,0 +1,46 @@
+#! /usr/bin/env python3
+
+import os
+from pathlib import Path
+from importlib.resources import files
+import __main__
+
+
+def root_dir():
+    if "FILE_NAME" in os.environ:
+        return Path(os.environ["FILE_NAME"]).parent()
+
+    if __main__.__package__:
+        return files(__main__.__package__)
+
+    # Use the folder of the main file as toml_dir.
+    if "__file__" in dir(__main__):
+        toml_dir = Path(__main__.__file__).parent
+        return toml_dir
+
+    # Find the path of the ipython notebook.
+    try:
+        import ipynbname
+
+        return ipynbname.path().parent
+    except IndexError:
+        pass
+
+    return Path(os.path.abspath("."))
+
+
+def root_file():
+    if "FILE_NAME" in os.environ:
+        return Path(os.environ["FILE_NAME"])
+
+    if "__file__" in dir(__main__):
+        return Path(__main__.__file__)
+
+    try:
+        import ipynbname
+
+        return ipynbname.path()
+    except IndexError:
+        pass
+
+    raise NotImplementedError
diff --git a/src/timing.py b/src/timing.py
new file mode 100644
index 0000000..b7fac76
--- /dev/null
+++ b/src/timing.py
@@ -0,0 +1,35 @@
+#! /usr/bin/env python3
+# vim:fenc=utf-8
+from time import time
+
+class ReportTime:
+    def __init__(self):
+        self.i = 0
+        self.last_t = time()
+        self.t = {}
+
+    def __call__(self, name=None):
+        t = time()
+        name = self.i if name is None else name
+        self.t[name] = [t - self.last_t]
+        self.i += 1
+        self.last_t = time()
+
+    def next(self):
+        self.i = 0
+        self.__call__ = self.call_next
+
+    def call_next(self, name=None):
+        t = time()
+        name = self.i if name is None else name
+        self.t[name].append(t - self.last_t)
+        self.i += 1
+        self.last_t = time()
+
+    def __repr__(self):
+        out = []
+        for i, t in self.t.items():
+            t = sum(t) / len(t)
+            out.append(f"{i}={t:.4f}")
+        return "\n".join(out)
+
diff --git a/src/vis.py b/src/vis.py
new file mode 100644
index 0000000..8328ecd
--- /dev/null
+++ b/src/vis.py
@@ -0,0 +1,46 @@
+#! /usr/bin/env python3
+# vim:fenc=utf-8
+import jax
+import numpy as np
+from PIL import Image
+
+def to_rgb(x):
+    x = x / x.max() * 255
+    x = np.broadcast_to(x, (3, x.shape[1], x.shape[2]))
+    return x.astype("uint8")
+
+
+def to_img(x, scale_up=10):
+    x = to_rgb(x)
+
+    img = np.empty(
+        (x.shape[1] * scale_up, x.shape[2] * scale_up, x.shape[0]), dtype=np.uint8
+    )
+
+    for color in range(x.shape[0]):
+        for row in range(x.shape[1]):
+            for col in range(x.shape[2]):
+                pixel = x[color, row, col]
+                new_row = row * scale_up
+                new_col = col * scale_up
+                img[
+                    new_row : new_row + scale_up,
+                    new_col : new_col + scale_up,
+                    color,
+                ] = pixel
+    if x.shape[0] == 1:
+        return Image.fromarray(img.squeeze())
+    else:
+        return Image.fromarray(img, "RGB")
+
+
+def color_mask(x, mask, color=np.array([255, 0, 0])):
+    if len(mask.shape) == 2:
+        mask = np.broadcast_to(mask, (3, mask.shape[0], mask.shape[1]))
+
+    x = to_rgb(x)
+    x = x * (1 - mask)
+    color = jax.vmap(lambda x, y: x * y, (0, 0))(color, mask)
+    x = x + color
+
+    return x