Fix memmap path and add grid size debug print

Author: fcladera

scripts/tile_composer.py

@@ -98,9 +98,11 @@ def download_and_save(lat_max, lat_min, lon_min, lon_max, zoom, image_name):
     num_y = y_max - y_min + 1
 
 
+    print(f"Tile grid: {num_x}x{num_y} tiles")
+
     tile_size = None
     headers = {'User-Agent': 'Mozilla/5.0'}
-    mmap_path = f"{image_name}_canvas.dat"
+    mmap_path = f"/tmp/tile_canvas_{os.getpid()}.dat"
 
     # Clean up stale memmap from a previous run
     if os.path.exists(mmap_path):