ISC21 Team from Nanyang Technological University - Fixed ScaLapack related bug

Hi, this is Shenggui from the Nanyang Technological University in ISC21. Sorry that the previous merge request was closed as the CI/CD pipeline was not run for some reason and I deleted the source branch after a merge in my workspace. As suggested by @askhl in #269 (closed), the bug is due to a missing broadcast operation.

I have run the sample code provided in that issue with version 21.1.0 and it throws exceptions directly instead of running for many iterations without convergence. The error is shown in err.log. This error occurs in the iterate_one_k_point method of Davidson solver. In this method, only this line in the subspace_diagonalize method is related to scalapack.

We dig deeper into this line and found that eps is only broadcast in the case when rows * columns is 1. This can be fixed by shifting the broadcast down to cover all cases.

The output file after making this change is water.out