GpuLaneBroadcast¶

The value an expression has in the first lane of the iteration.

Declaration¶

Syntax¶

GpuLaneBroadcast(expr arg, ttype type, expr? value)

Arguments¶

Argument	Description
`arg`	an integer, real or logical scalar.
`type`	the type of `arg`.
`value`	always `nil`.

Return values¶

The value arg has in lane zero of the running thread's iteration.

Description¶

In a kernel whose layout has lanes (see gpu_kernel_layout), a statement that must not be repeated by every lane of an iteration -- it writes memory the lanes share, or takes elements of the device heap -- runs on the first lane only. Each lane holds its own copy of a scalar local, so after the statement every lane takes the scalars it assigned from the first one: x = GpuLaneBroadcast(x). Every lane of the iteration evaluates it at the same point. Only such a kernel has one.

Examples¶

(GpuLaneBroadcast
  (Var 2 x)
  (Integer
    :kind 4
  )
  ()
)