Implement in-place contract! methods

src/Numerics.jl

@@ -42,13 +42,9 @@ function contract(a::Tensor, b::Tensor; dims=(∩(inds(a), inds(b))), out=nothin
         out
     end
 
-    _ia = __omeinsum_sym2str(ia)
-    _ib = __omeinsum_sym2str(ib)
-    _ic = __omeinsum_sym2str(ic)
-
-    data = EinCode((_ia, _ib), _ic)(parent(a), parent(b))
-
-    return Tensor(data, ic)
+    data = OMEinsum.get_output_array((parent(a), parent(b)), [size(i in ia ? a : b, i) for i in ic]; fillzero=false)
+    c = Tensor(data, ic)
+    return contract!(c, a, b)
 end
 
 function contract(a::Tensor; dims=nonunique(inds(a)), out=nothing)
@@ -61,9 +57,9 @@ function contract(a::Tensor; dims=nonunique(inds(a)), out=nothing)
         out
     end
 
-    data = EinCode((String.(ia),), String.(ic))(parent(a))
-
-    return Tensor(data, ic)
+    data = OMEinsum.get_output_array((parent(a),), [size(a, i) for i in ic]; fillzero=false)
+    c = Tensor(data, ic)
+    return contract!(c, a)
 end
 
 contract(a::Union{T,AbstractArray{T,0}}, b::Tensor{T}) where {T} = contract(Tensor(a), b)
@@ -72,6 +68,26 @@ contract(a::AbstractArray{<:Any,0}, b::AbstractArray{<:Any,0}) = only(contract(T
 contract(a::Number, b::Number) = contract(fill(a), fill(b))
 contract(tensors::Tensor...; kwargs...) = reduce((x, y) -> contract(x, y; kwargs...), tensors)
 
+function contract!(c::Tensor, a::Tensor, b::Tensor)
+    ixs = (inds(a), inds(b))
+    iy = inds(c)
+    xs = (parent(a), parent(b))
+    y = parent(c)
+    size_dict = merge!(Dict{Symbol,Int}.([inds(a) .=> size(a), inds(b) .=> size(b)])...)
+
+    einsum!(ixs, iy, xs, y, true, false, size_dict)
+    return c
+end
+
+function contract!(y::Tensor, x::Tensor)
+    ixs = (inds(x),)
+    iy = inds(y)
+    size_dict = Dict{Symbol,Int}(inds(x) .=> size(x))
+
+    einsum!(ixs, iy, (parent(x),), parent(y), true, false, size_dict)
+    return y
+end
+
 """
     *(::Tensor, ::Tensor)