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Support matrix multiplication (Continue #93) #146

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f34598c
Preliminary support for matrix multiplication.
Jan 3, 2020
0529fe8
use offsets instead of axes
jishnub Sep 14, 2020
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20 changes: 20 additions & 0 deletions src/OffsetArrays.jl
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
module OffsetArrays

using Base: Indices, tail, @propagate_inbounds

@static if !isdefined(Base, :IdentityUnitRange)
const IdentityUnitRange = Base.Slice
else
Expand Down Expand Up @@ -45,10 +46,12 @@ OffsetArray(A::AbstractArray{T,N}, offsets::Vararg{Int,N}) where {T,N} =
OffsetArray(A, offsets)
OffsetArray(A::AbstractArray{T,0}) where {T} = OffsetArray(A, ())

# Create an uninitialized OffsetArray with given element type
const ArrayInitializer = Union{UndefInitializer, Missing, Nothing}
OffsetArray{T,N}(init::ArrayInitializer, inds::Indices{N}) where {T,N} =
OffsetArray(Array{T,N}(init, map(indexlength, inds)), map(indexoffset, inds))
OffsetArray{T}(init::ArrayInitializer, inds::Indices{N}) where {T,N} = OffsetArray{T,N}(init, inds)
# Same thing, but taking multiple args for offsets/indices
OffsetArray{T,N}(init::ArrayInitializer, inds::Vararg{AbstractUnitRange,N}) where {T,N} = OffsetArray{T,N}(init, inds)
OffsetArray{T}(init::ArrayInitializer, inds::Vararg{AbstractUnitRange,N}) where {T,N} = OffsetArray{T,N}(init, inds)

Expand Down Expand Up @@ -402,6 +405,23 @@ end

no_offset_view(A::OffsetArray) = no_offset_view(parent(A))

# Quick hack for matrix multiplication.
# Ideally, one would instead improve LinearAlgebra's support of custom indexing.
function Base.:(*)(A::OffsetMatrix, B::OffsetMatrix)
matmult_check_axes(A, B)
C = parent(A) * parent(B)
OffsetArray{eltype(C), 2, typeof(C)}(C, (A.offsets[1], B.offsets[2]))
end

function Base.:(*)(A::OffsetMatrix, B::OffsetVector)
matmult_check_axes(A, B)
C = parent(A) * parent(B)
OffsetArray{eltype(C), 1, typeof(C)}(C, (A.offsets[1], ))
end
function matmult_check_axes(A, B)
axes(A, 2) === axes(B, 1) || axes(A, 2) == axes(B, 1) ||
error("axes(A,2) = $(UnitRange(axes(A,2))) does not equal axes(B,1) = $(UnitRange(axes(B,1)))")
end

####
# work around for segfault in searchsorted*
Expand Down
31 changes: 31 additions & 0 deletions test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -946,3 +946,34 @@ end
@test searchsorted(o, 5) == 2:2
@test searchsorted(o, 6) == 3:2
end

@testset "Matrix multiplication" begin
a = [1 2; 3 4]
v = [5, 6]
oa = OffsetArray(a, (2, 2))
ov = OffsetVector(v, (2,))

@test parent(oa * oa) == a * a
@test axes(oa * oa) == axes(oa)

@test parent(oa * ov) == a * v
@test axes(oa * ov) == (axes(oa, 1),)

@test parent(ones(2, 2:3) * ones(2:3, 3:5)) == ones(2, 2) * ones(2, 3)
@test axes(ones(2, 2:3) * ones(2:3, 3:5)) == (1:2, 3:5)

@test parent(ones(2, 2:3) * ones(2:3)) == ones(2, 2) * ones(2)
@test axes(ones(2, 2:3) * ones(2:3)) == (1:2,)

# One-based arrays
oa2 = OffsetArray(a, axes(a))
@test oa2 * a == a * a
@test a * oa2 == a * a

@test oa2 * v == a * v
@test v' * oa2 == v' * a

@test_throws Exception zeros(2, 2:3) * zeros(2:4, 2)
@test_throws Exception zeros(2, 2:3) * zeros(3:4, 2)
@test_throws Exception zeros(2, 2:3) * zeros(2:4)
end