julia/src/context.jl

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@enum CONTEXT_TYPE CPU=1 GPU=2 CPU_PINNED=3

Base.convert(::Type{CONTEXT_TYPE}, x::Integer) = CONTEXT_TYPE(x)

"""
    Context(dev_type, dev_id)

A context describes the device type and id on which computation should be carried on.
"""
struct Context
  device_type::CONTEXT_TYPE
  device_id::Int

  Context(dev_type::CONTEXT_TYPE, dev_id::Integer = 0) = new(dev_type, dev_id)
end

Context(dev_type::Integer, dev_id::Integer = 0) =
  Context(convert(CONTEXT_TYPE, dev_type), dev_id)

Base.show(io::IO, ctx::Context) =
  print(io, "$(ctx.device_type)$(ctx.device_id)")

"""
    cpu(dev_id)

Get a CPU context with a specific id. `cpu()` is usually the default context for many
operations when no context is specified.

# Arguments
* `dev_id::Integer = 0`: the CPU id.
"""
cpu(dev_id::Integer = 0) = Context(CPU, dev_id)

"""
    gpu(dev_id)

Get a GPU context with a specific id. The K GPUs on a node is typically numbered as 0,...,K-1.

# Arguments
* `dev_id::Integer = 0` the GPU device id.
"""
gpu(dev_id::Integer = 0) = Context(GPU, dev_id)