Remove Managed Memory Workarounds (#793)

Two changes:
- the AMReX default for `the_arena_is_managed` is false for a while,
  so we do not need to "overwrite" it anymore
- our initial implementation of particle loss in apertures was reworked
  for a while and does not require managed GPU memory anymore: remove
  work-arounds in inputs

docs/source/usage/parameters.rst

@@ -813,7 +813,7 @@ Overall simulation parameters
 * ``amrex.the_arena_is_managed``  (``0`` or ``1``; default is ``0`` for false)
     When running on GPUs, device memory that is accessed from the host will automatically be transferred with managed memory.
     This is useful for convenience during development, but has sometimes severe performance and memory footprint implications if relied on (and sometimes vendor bugs).
-    For all regular ImpactX operations, we therefore do explicit memory transfers without the need for managed memory and thus changed the AMReX default to false.
+    For all regular ImpactX operations, we therefore do explicit memory transfers without the need for managed memory.
     `Please also see the documentation in AMReX <https://amrex-codes.github.io/amrex/docs_html/GPU.html#inputs-parameters>`__.
 
 * ``amrex.omp_threads``  (``system``, ``nosmt`` or positive integer; default is ``nosmt``)

examples/aperture/input_aperture.in

@@ -35,9 +35,6 @@ collimator.shape = rectangular
 collimator.xmax = 1.0e-3
 collimator.ymax = 1.5e-3
 
-# work-around for https://github.com/ECP-WarpX/impactx/issues/499
-amrex.the_arena_is_managed = 1
-
 
 ###############################################################################
 # Algorithms

examples/aperture/run_absorber.py

@@ -6,13 +6,8 @@
 #
 # -*- coding: utf-8 -*-
 
-import amrex.space3d as amr
 from impactx import ImpactX, distribution, elements
 
-# work-around for https://github.com/ECP-WarpX/impactx/issues/499
-pp_amrex = amr.ParmParse("amrex")
-pp_amrex.add("the_arena_is_managed", 1)
-
 sim = ImpactX()
 
 # set numerical parameters and IO control

examples/aperture/run_aperture.py

@@ -6,13 +6,8 @@
 #
 # -*- coding: utf-8 -*-
 
-import amrex.space3d as amr
 from impactx import ImpactX, distribution, elements
 
-# work-around for https://github.com/ECP-WarpX/impactx/issues/499
-pp_amrex = amr.ParmParse("amrex")
-pp_amrex.add("the_arena_is_managed", 1)
-
 sim = ImpactX()
 
 # set numerical parameters and IO control

examples/aperture/run_aperture_periodic.py

@@ -6,13 +6,8 @@
 #
 # -*- coding: utf-8 -*-
 
-import amrex.space3d as amr
 from impactx import ImpactX, distribution, elements
 
-# work-around for https://github.com/ECP-WarpX/impactx/issues/499
-pp_amrex = amr.ParmParse("amrex")
-pp_amrex.add("the_arena_is_managed", 1)
-
 sim = ImpactX()
 
 # set numerical parameters and IO control

tests/python/conftest.py

@@ -32,8 +32,6 @@ def amrex_init(tmpdir):
                 "amrex.signal_handling=0",
                 # abort GPU runs if out-of-memory instead of swapping to host RAM
                 "amrex.abort_on_out_of_gpu_memory=1",
-                # do not rely on implicit host-device memory transfers
-                "amrex.the_arena_is_managed=0",
             ]
         )
         yield