add N for hardware indices

Author: vchuravy

src/KernelAbstractions.jl

@@ -16,13 +16,15 @@ using StaticArrays
 using Adapt
 
 """
-    @kernel function f(args) end
+    @kernel [N] function f(args) end
 
 Takes a function definition and generates a [`Kernel`](@ref) constructor from it.
 The enclosed function is allowed to contain kernel language constructs.
 In order to call it the kernel has first to be specialized on the backend
 and then invoked on the arguments.
 
+The optional `N` parameter can be used to fix the number of dimensions used for the ndrange.
+
 # Kernel language
 
 - [`@Const`](@ref)
@@ -54,7 +56,7 @@ macro kernel(expr)
 end
 
 """
-    @kernel config function f(args) end
+    @kernel [N] config function f(args) end
 
 This allows for two different configurations:
 
@@ -584,17 +586,17 @@ in a workgroup.
     ```
     As well as the on-device functionality.
 """
-struct Kernel{Backend, WorkgroupSize <: _Size, NDRange <: _Size, Fun}
+struct Kernel{Backend, N, WorkgroupSize <: _Size, NDRange <: _Size, Fun}
     backend::Backend
     f::Fun
 end
 
-function Base.similar(kernel::Kernel{D, WS, ND}, f::F) where {D, WS, ND, F}
-    Kernel{D, WS, ND, F}(kernel.backend, f)
+function Base.similar(kernel::Kernel{D, N, WS, ND}, f::F) where {D, N, WS, ND, F}
+    Kernel{D, N, WS, ND, F}(kernel.backend, f)
 end
 
-workgroupsize(::Kernel{D, WorkgroupSize}) where {D, WorkgroupSize} = WorkgroupSize
-ndrange(::Kernel{D, WorkgroupSize, NDRange}) where {D, WorkgroupSize, NDRange} = NDRange
+workgroupsize(::Kernel{D, N, WorkgroupSize}) where {D, WorkgroupSize} = WorkgroupSize
+ndrange(::Kernel{D, N, WorkgroupSize, NDRange}) where {D, WorkgroupSize, NDRange} = NDRange
 backend(kernel::Kernel) = kernel.backend
 
 """
@@ -657,8 +659,8 @@ Partition a kernel for the given ndrange and workgroupsize.
     return iterspace, dynamic
 end
 
-function construct(backend::Backend, ::S, ::NDRange, xpu_name::XPUName) where {Backend <: Union{CPU, GPU}, S <: _Size, NDRange <: _Size, XPUName}
-    return Kernel{Backend, S, NDRange, XPUName}(backend, xpu_name)
+function construct(backend::Backend, ::Val{N}, ::S, ::NDRange, xpu_name::XPUName) where {Backend <: Union{CPU, GPU}, N, S <: _Size, NDRange <: _Size, XPUName}
+    return Kernel{Backend, N, S, NDRange, XPUName}(backend, xpu_name)
 end
 
 ###