Conduit Device Support

[JustinPrivitera]

Resolves #1358

TODO
Make ticket for follow-on work:

• You can create a "parallel" exec policy that is_parallel_policy() returns false for. We should examine in the future if we want consistency with the policies.
• init_device_memory_handlers() should be a static function that people only have to do once. We should have a conduit utility somewhere that should be able to do this somewhere. It should see if the handlers are installed and do it, otherwise do nothing.

[JustinPrivitera]

Running with much larger arrays, src starting on host des starting on device

[ RUN      ] conduit_execution.strawman_data_accessor_src_host_des_device
[/usr/workspace/justin/conduit_builds/develop_04_03_2026_HIP/conduit/src/tests/conduit/t_conduit_execution.cpp : 1079]
 data_accessor sync policy=host src_start=host des_start=device
Path     Min time/rank Max time/rank Avg time/rank Time %    
use_with      0.001430      0.001430      0.001430  1.311628 
forall        0.106097      0.106097      0.106097 97.336826 
sync          0.001413      0.001413      0.001413  1.296252 
[/usr/workspace/justin/conduit_builds/develop_04_03_2026_HIP/conduit/src/tests/conduit/t_conduit_execution.cpp : 1107]
 data_accessor sync policy=device src_start=host des_start=device
Path     Min time/rank Max time/rank Avg time/rank Time %    
use_with      0.008063      0.008063      0.008063 98.000095 
forall        0.000116      0.000116      0.000116  1.414218 
sync          0.000000      0.000000      0.000000  0.003525 
[/usr/workspace/justin/conduit_builds/develop_04_03_2026_HIP/conduit/src/tests/conduit/t_conduit_execution.cpp : 1135]
 data_accessor assume policy=host src_start=host des_start=device
Path     Min time/rank Max time/rank Avg time/rank Time %    
use_with      0.001418      0.001418      0.001418  1.348748 
forall        0.103654      0.103654      0.103654 98.604876 
assume        0.000001      0.000001      0.000001  0.001389 
[/usr/workspace/justin/conduit_builds/develop_04_03_2026_HIP/conduit/src/tests/conduit/t_conduit_execution.cpp : 1163]
 data_accessor assume policy=device src_start=host des_start=device
Path     Min time/rank Max time/rank Avg time/rank Time %    
use_with      0.007959      0.007959      0.007959 98.013778 
forall        0.000115      0.000115      0.000115  1.415281 
assume        0.000000      0.000000      0.000000  0.003941 
[/usr/workspace/justin/conduit_builds/develop_04_03_2026_HIP/conduit/src/tests/conduit/t_conduit_execution.cpp : 1190]
 data_accessor active_space src_start=host des_start=device
Path     Min time/rank Max time/rank Avg time/rank Time %    
use_with      0.001423      0.001423      0.001423  1.318741 
forall        0.105016      0.105016      0.105016 97.324327 
sync          0.001414      0.001414      0.001414  1.310595 
[       OK ] conduit_execution.strawman_data_accessor_src_host_des_device (1106 ms)

[JustinPrivitera]

I am confused by this

[JustinPrivitera]

wherever this method is called, we want to take a look at the template and consider switching to a policy object choice.

[JustinPrivitera]

look into RDC before getting Cyrus' blessing

[JustinPrivitera]

use hatchet/thicket to compare speedup

[JustinPrivitera]

let's see if @cyrush likes the comment up above

[JustinPrivitera]

this is bad

@cyrush doesn't like it :(

[JustinPrivitera]

conditional in the hot path of the loop is really bad

compile with the atomic policy - template, not runtime policy

[JustinPrivitera]

why do we need to include these into conduit core and conduit? Can't we just have them be included into cpp files and not headers? Then can we just use CONDUIT_USE_*** instead?