GpuLaneReduce¶

What the lanes of the iteration hold, combined.

Declaration¶

Syntax¶

GpuLaneReduce(expr arg, reduction_op op, ttype type, expr? value)

Arguments¶

Argument	Description
`arg`	an integer or real scalar.
`op`	how the values combine: `ReduceAdd`, `ReduceMul`, `ReduceMIN` or `ReduceMAX`.
`type`	the type of `arg`.
`value`	always `nil`.

Return values¶

The values arg has in the lanes of the running thread’s iteration, combined by op, in every lane.

Description¶

In a kernel whose layout has lanes (see gpu_kernel_layout), the lanes of an iteration may share out a loop that accumulates into private scalars – the inner product of a matrix-vector product, the forces on one body – each accumulating its iterations from the identity of the operation (the first lane from the value the scalar had before the loop). After the loop every lane takes what all of them hold: s = GpuLaneReduce(s, ReduceAdd). Every lane of the iteration evaluates it at the same point. Only a kernel for a device whose lanes can combine values has one (GpuDeviceCapabilities::lane_reductions, see gpu_vector_lanes.cpp).

Examples¶

(GpuLaneReduce
  (Var 2 t)
  ReduceAdd
  (Real
    :kind 8
  )
  ()
)