viewer: --device=cpu

[thowell]

make viewer compatible with device=cpu

mjwarp-viewer benchmarks/humanoid/humanoid.xml --nconmax=48 --njmax=128 --device=cpu

[erikfrey]

Looks great, just a couple questions around keeping the code simple

[erikfrey]

scopedcapture has a device param - could you do that instead of adding the ScopedDevice above?

[erikfrey]

nit: we can use the graph itself as a sentinel, so this could be something like:

graph = _compile_step(m, d) if wp.get_device().is_cuda else None

then further down

if graph is None:
  print("Running Warp unoptimized on CPU.")
  mjw.step(m, d)  # warmup

...
if _VIEWER_GLOBAL_STATE["running"] or _VIEWER_GLOBAL_STATE["step_once"]:
  _VIEWER_GLOBAL_STATE["step_once"] = False
  if graph is None:
    mjw.step(m, d)
  else:
    wp.capture_launch(graph)
    wp.synchronize()

something like that?