Long-lived per-machine GPU node. A named GenServer that owns the spirit VkPipelineCache, the persistent buffer registry, and the watchdog/timeout layer. Clients submit work via with_node/2 (or the lower-level exec/2); the node serializes execution and reports timeouts/dead-server/etc. as error tuples.

This is the GPU-only generic core. MCMC / NUTS / sampler-specific dispatch logic lives in Exmc.NUTS.Vulkan.Dispatch (or any other client) and calls into this node via with_node/2.

Lifecycle

Start under your application's supervisor:

children = [
  {Nx.Vulkan.Node, []}
]

Or for ad-hoc use (REPL, benchmarks):

{:ok, _pid} = Nx.Vulkan.Node.start_link()

Generic dispatch

with_node/2 runs an arbitrary 0-arity function inside the GenServer process. The function has access to the spirit pipeline cache (loaded once at init) and may stash per-shader buffer state in process dict.

result = Nx.Vulkan.Node.with_node(fn ->
  # any GPU work — uses Nx.Vulkan.Native NIFs directly,
  # serialized through this GenServer process.
  Nx.Vulkan.Native.leapfrog_chain_synth(q, p, m, push, k, spv)
end)

Returns the function's return value, or {:error, reason} on watchdog timeout / dead node.

Watchdog

Reads Application.get_env(:nx_vulkan, :node_timeout_ms, :infinity). On timeout the calling process gets {:error, :node_timeout} and is free to fall back to a CPU/EXLA path. The GenServer process itself remains blocked on the in-flight NIF call until that returns — by design; cancelling Vulkan dispatches mid-flight is unsafe.