Remove USE_ACC

[joshkamm]

I'm currently talking with Paul and he thinks we should remove the USE_ACC preprocessor directive. I think we could start by writing a python script to find all snippets of form

#if USE_ACC
 #pragma acc
#endif
  for

and delete the #if and #endif lines. Then we could go through manually and clean up the rest.

[joshkamm]

@ndmeier25 this came up earlier today talking with Paul. If you're up for working on it I can explain in more detail what Paul was thinking. Otherwise I can work on it when I get a chance

[joshkamm]

@paulzim46 I see that some of your changes to SlaterGPU (https://github.com/ZimmermanGroup/SlaterGPU/pull/14/files) overlap with USE_ACC statements. If we remove them starting from the main branch it will likely be difficult to merge those changes with yours. Would it make sense to remove them starting from your branch and target multiple GPU support for your new electronic structure package instead of FancyElectrons? And should we wait until you're mostly done making changes to SlaterGPU since these preprocessor directives are pretty pervasive and could easily conflict with a lot of things?

[joshkamm]

I'm currently talking with Paul and he is planning to remove all of the USE_ACC statements in his zsgpu branch so that this will be taken care of when we merge that branch.