global_max doesn't work with AMR

[philip-blakely]

Describe the bug

The new global_max (and probably other similar operators) only work on a per-patch basis with AMR. They should work across all patches (and levels).

Helpful additional information

• Did VisIt crash: No
• Did you get wrong results: Yes

To Reproduce

Open an AMR data-set, and create an expression using global_max. For example with the attached dataset:

max_density_grad = global_max(magnitude(gradient(Air_density)))

Plotting this shows that the global maximum is actually done on a per-patch basis, not a global level as suggested by the name.

Expected behavior

I would expect the global_max() to work across all AMR patches and levels. This would allow the simplification of (for example) a mock-schlieren plot for highlighting density discontinuities.

Although I haven't generated any test-data yet, there may also be issues when multi-material data is involved as well, e.g. restricting plotting to a specific material that does not exist on some patches. However, this may be solved by debugging the primary issue.

Attachments

• AMReX-output (BoxLib format) is attached showing the end of a simulation where a shock impacts a bubble.
  shock_bubble_data.zip

• VisIt session-file is:
  schlieren_issue.session.zip

and you can plot either Air_sch or Air_sch_old to see the screenshots below.
In case the session file doesn't work:

density_grad = magnitude(gradient(Air_density))
Air_sch = exp(-20*density_grad/global_max(density_grad))
Air_sch_old = exp(-20*density_grad/824)

Relevant screenshots:
If I compute the global_max() manually (by checking plot limits on magnitude(gradient(density))) then I can get a mock-schlieren plot that looks correct:

If I use global_max instead, I get the following:

Desktop

• OS and version: Ubuntu 24.04
• VisIt Version: 3.4.2