Invalid cube file

General Discussion
1

In attempting to open a particular cube file, I get the following error:

Error while reading file ... . Invalid cube file.

problem_cube.txt (6.0 MB)

I generated a simpler (smaller) test cube file with the same code and it opens fine. Note the trouble one opens and visualizes just fine with IQmol.

fine_cube.txt (338.9 KB)

Any idea what could be wrong?

2

Yes. Internally, we store Cube data as float instead of double to save memory. We’re generally only rendering orbitals, etc. so the loss of precision isn’t a big deal and lets users handle larger cubes on lower-end hardware.

In this case, there was an underflow - a value too small for a float. Clearly that bug has been there for ages, but no one reported it.

Now, it reads in double and converts to float (e.g., 1.0e-34 => 0.0)