Speedup ABLStats

[marchdf]

Summary

This speeds up the ABL stats considerably. For the precursor I was profiling, compute_zi took 27% of the total runtime (!). This takes it down to just 1%. Currently just for nvidia GPU. Need to generalize.

More granular profiling of the ABLStats.

Pull request type

Please check the type of change introduced:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

The following is included:

• new unit-test(s)
• new regression test(s)
• documentation for new capability

This PR was tested by running:

• the unit tests
  • on GPU
  • on CPU
• the regression tests
  • on GPU
  • on CPU

Additional background

Issue Number:

[marchdf]

Before change in compute_zi:

Time spent in Evolve():      69.93182354

After:

Time spent in Evolve():      47.23603398

1.5X speedup for total simulation.