debug: re-add cell progress log to find new crash point in demo.py

The crash moved to a later cell after removing N=50M and fixing max_iter.
Re-add per-cell logging to identify the new offending cell.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: larsgeb

demo.py

@@ -424,7 +424,9 @@ def logstar(x, base=np.e, threshold=1.0):
 ax.imshow(logn1p(mandel_gpu, n=50), cmap="inferno", extent=[-2, 1, -1.5, 1.5], origin="lower")
 ax.set_xlabel("Re(c)")
 ax.set_ylabel("Im(c)")
-ax.set_title(f"Mandelbrot Set — {width}x{height}, max_iter={max_iter_vis}\nGPU time: {t_gpu * 1e3:.1f} ms")
+ax.set_title(
+    f"Mandelbrot Set — {width}x{height}, max_iter={max_iter_vis}\nGPU time: {t_gpu * 1e3:.1f} ms"
+)
 plt.tight_layout()
 plt.show()
 

scripts/render_notebooks.py

@@ -82,6 +82,9 @@ def _patched_show(*_args, **_kwargs) -> None:
         if not src:
             continue
 
+        preview = src.splitlines()[0][:60]
+        print(f"  [cell {exec_count}] {preview}", file=sys.__stdout__, flush=True)
+
         cell_images.clear()
         stdout_buf = io.StringIO()