allow switching backends

src/NDTensors.jl

@@ -173,6 +173,9 @@ function __init__()
     enable_tblis()
     include("tblis.jl")
   end
+  @require Octavian = "6fd5a793-0b7e-452c-907f-f8bfe9c57db4" begin
+      include("octavian.jl")
+  end
 end
 
 end # module NDTensors

src/dense.jl

@@ -1,6 +1,7 @@
 #
 # Dense storage
 #
+using LinearAlgebra: BlasFloat
 
 struct Dense{ElT, VecT<:AbstractVector} <: TensorStorage{ElT}
   data::VecT
@@ -441,39 +442,61 @@ function outer!(R::DenseTensor{ElR},
   return R
 end
 
-# BLAS matmul
+export backend_auto, backend_blas, backend_generic
+
+@eval struct GemmBackend{T}
+  (f::Type{<:GemmBackend})() = $(Expr(:new, :f))
+end
+GemmBackend(s) = GemmBackend{Symbol(s)}()
+macro GemmBackend_str(s)
+    :(GemmBackend{$(Expr(:quote, Symbol(s)))})
+end
+
+const gemm_backend = Ref(:Auto)
+function backend_auto()
+    gemm_backend[] = :Auto
+end
+function backend_blas()
+    gemm_backend[] = :BLAS
+end
+function backend_generic()
+    gemm_backend[] = :Generic
+end
+
+@inline function auto_select_backend(::Type{<:StridedVecOrMat{<:BlasFloat}}, ::Type{<:StridedVecOrMat{<:BlasFloat}}, ::Type{<:StridedVecOrMat{<:BlasFloat}})
+    GemmBackend(:BLAS)
+end
+
+@inline function auto_select_backend(::Type{<:AbstractVecOrMat}, ::Type{<:AbstractVecOrMat}, ::Type{<:AbstractVecOrMat})
+    GemmBackend(:Generic)
+end
+
 function _gemm!(tA, tB, alpha,
-                A::AbstractVecOrMat{<:LinearAlgebra.BlasFloat},
-                B::AbstractVecOrMat{<:LinearAlgebra.BlasFloat},
-                beta, C::AbstractVecOrMat{<:LinearAlgebra.BlasFloat})
+                A::TA,
+                B::TB,
+                beta, C::TC) where {TA<:AbstractVecOrMat, TB<:AbstractVecOrMat, TC<:AbstractVecOrMat}
+    if gemm_backend[] == :Auto
+        _gemm!(auto_select_backend(TA, TB, TC), tA, tB, alpha, A, B, beta, C)
+    else
+        _gemm!(GemmBackend(gemm_backend[]), tA, tB, alpha, A, B, beta, C)
+    end
+end
+
+# BLAS matmul
+function _gemm!(::GemmBackend{:BLAS}, tA, tB, alpha,
+                A::AbstractVecOrMat,
+                B::AbstractVecOrMat,
+                beta, C::AbstractVecOrMat)
   #@timeit_debug timer "BLAS.gemm!" begin
   BLAS.gemm!(tA, tB, alpha, A, B, beta, C)
   #end # @timeit
 end
 
 # generic matmul
-function _gemm!(tA, tB, alpha::AT,
+function _gemm!(::GemmBackend{:Generic}, tA, tB, alpha::AT,
                 A::AbstractVecOrMat, B::AbstractVecOrMat,
                 beta::BT, C::AbstractVecOrMat) where {AT, BT}
-    if tA == 'T'
-        A = transpose(A)
-    end
-    if tB == 'T'
-        B = transpose(B)
-    end
-    if beta == zero(BT)
-        if alpha == one(AT)
-            C .= A * B
-        else
-            C .= alpha .* (A * B)
-        end
-    else
-        if alpha == one(AT)
-            C .= (A * B) .+ beta .* C
-        else
-            C .= alpha .* (A * B) .+ beta .* C
-        end
-    end
+    mul!(C, tA == 'T' ? transpose(A) : A, tB == 'T' ? transpose(B) : B, alpha, beta)
     return C
 end
 

src/octavian.jl

@@ -0,0 +1,14 @@
+using .Octavian
+
+export backend_octavian
+
+function backend_octavian()
+    gemm_backend[] = :Octavian
+end
+
+function _gemm!(::GemmBackend{:Octavian}, tA, tB, alpha,
+                A::AbstractVecOrMat,
+                B::AbstractVecOrMat,
+                beta, C::AbstractVecOrMat)
+    Octavian.matmul!(C, tA == 'T' ? transpose(A) : A, tB == 'T' ? transpose(B) : B, alpha, beta)
+end

test/dense.jl

@@ -1,6 +1,12 @@
 using NDTensors,
       Test
 
+@static if VERSION >= v"1.5"
+    using Pkg
+    Pkg.add("Octavian")
+    using Octavian
+end
+
 @testset "Dense Tensors" begin
 
 @testset "DenseTensor basic functionality" begin
@@ -210,6 +216,39 @@ end
   end
 end
 
+@testset "change backends" begin
+    a, b, c = [randn(5,5) for i=1:3]
+    backend_auto()
+    @test NDTensors.gemm_backend[] == :Auto
+    @test NDTensors.auto_select_backend(typeof.((a, b, c))...) == NDTensors.GemmBackend(:BLAS)
+    res1 = NDTensors._gemm!('N', 'N', 2.0, a, b, 0.2, copy(c))
+    backend_blas()
+    @test NDTensors.gemm_backend[] == :BLAS
+    res2 = NDTensors._gemm!('N', 'N', 2.0, a, b, 0.2, copy(c))
+    backend_generic()
+    @test NDTensors.gemm_backend[] == :Generic
+    res3 = NDTensors._gemm!('N', 'N', 2.0, a, b, 0.2, copy(c))
+    @test res1 == res2
+    @test res1 ≈ res3
+    backend_auto()
+end
+
+@static if VERSION >= v"1.5"
+    @testset "change backends" begin
+        a, b, c = [randn(5,5) for i=1:3]
+        backend_auto()
+        @test NDTensors.gemm_backend[] == :Auto
+        @test NDTensors.auto_select_backend(typeof.((a, b, c))...) == NDTensors.GemmBackend(:BLAS)
+        res1 = NDTensors._gemm!('N', 'N', 2.0, a, b, 0.2, copy(c))
+        backend_octavian()
+        @test NDTensors.gemm_backend[] == :Octavian
+        res4 = NDTensors._gemm!('N', 'N', 2.0, a, b, 0.2, copy(c))
+        @test res1 ≈ res4
+        backend_auto()
+    end
+end
+
 end
+
 nothing