[AlgorithmSelection] Rename BackendSelection, introduce Backend type (#1407)

Author: mtfishman

NDTensors/src/blocksparse/contract.jl

@@ -1,4 +1,4 @@
-using .AlgorithmSelection: Algorithm, @Algorithm_str
+using .BackendSelection: Algorithm, @Algorithm_str
 
 function contract(
   tensor1::BlockSparseTensor,

NDTensors/src/imports.jl

@@ -22,8 +22,8 @@ using TimerOutputs
 using TupleTools
 
 for lib in [
-  :AlgorithmSelection,
   :AllocateData,
+  :BackendSelection,
   :BaseExtensions,
   :UnspecifiedTypes,
   :TypeParameterAccessors,
@@ -51,6 +51,10 @@ for lib in [
   include("lib/$(lib)/src/$(lib).jl")
   @eval using .$lib: $lib
 end
+# TODO: This is defined for backwards compatibility,
+# delete this alias once downstream packages change over
+# to using `BackendSelection`.
+const AlgorithmSelection = BackendSelection
 
 using Base: @propagate_inbounds, ReshapedArray, DimOrInd, OneTo
 

NDTensors/src/lib/AlgorithmSelection/src/AlgorithmSelection.jl

@@ -0,0 +1,9 @@
+module BackendSelection
+include("abstractbackend.jl")
+include("backend_types.jl")
+
+# TODO: This is defined for backwards compatibility,
+# delete this alias once downstream packages change over
+# to using `BackendSelection`.
+const AlgorithmSelection = BackendSelection
+end

NDTensors/src/lib/AlgorithmSelection/src/algorithm.jl

@@ -0,0 +1,4 @@
+abstract type AbstractBackend end
+
+backend_string(::AbstractBackend) = error("Not implemented")
+parameters(::AbstractBackend) = error("Not implemented")

NDTensors/src/lib/AlgorithmSelection/test/runtests.jl

@@ -0,0 +1,57 @@
+for type in (:Algorithm, :Backend)
+  @eval begin
+    """
+        $($type)
+
+    A type representing a backend for a function.
+
+    For example, a function might have multiple backends
+    implementations, which internally are selected with a `$($type)` type.
+
+    This allows users to extend functionality with a new implementation but
+    use the same interface.
+    """
+    struct $type{Back,Kwargs<:NamedTuple} <: AbstractBackend
+      kwargs::Kwargs
+    end
+
+    $type{Back}(kwargs::NamedTuple) where {Back} = $type{Back,typeof(kwargs)}(kwargs)
+    $type{Back}(; kwargs...) where {Back} = $type{Back}(NamedTuple(kwargs))
+    $type(s; kwargs...) = $type{Symbol(s)}(NamedTuple(kwargs))
+
+    $type(backend::$type) = backend
+
+    # TODO: Use `SetParameters`.
+    backend_string(::$type{Back}) where {Back} = string(Back)
+    parameters(backend::$type) = getfield(backend, :kwargs)
+
+    function Base.show(io::IO, backend::$type)
+      return print(io, "$type type ", backend_string(backend), ", ", parameters(backend))
+    end
+    Base.print(io::IO, backend::$type) =
+      print(io, backend_string(backend), ", ", parameters(backend))
+  end
+end
+
+# TODO: See if these can be moved inside of `@eval`.
+"""
+    @Algorithm_str
+
+A convenience macro for writing [`Algorithm`](@ref) types, typically used when
+adding methods to a function that supports multiple algorithm
+backends.
+"""
+macro Algorithm_str(s)
+  return :(Algorithm{$(Expr(:quote, Symbol(s)))})
+end
+
+"""
+    @Backend_str
+
+A convenience macro for writing [`Backend`](@ref) types, typically used when
+adding methods to a function that supports multiple
+backends.
+"""
+macro Backend_str(s)
+  return :(Backend{$(Expr(:quote, Symbol(s)))})
+end