Fix tall qr multiplication (#38002) (#38360)

(cherry picked from commit 24750c6) Co-authored-by: Daniel Karrasch <[email protected]>
JuliaLang · Nov 9, 2020 · 04ba8e0 · 04ba8e0
1 parent 006853a
commit 04ba8e0
Show file tree

Hide file tree

Showing 2 changed files with 20 additions and 1 deletion.
diff --git a/stdlib/LinearAlgebra/src/qr.jl b/stdlib/LinearAlgebra/src/qr.jl
@@ -749,7 +749,19 @@ function *(adjA::Adjoint{<:Any,<:StridedVecOrMat}, adjQ::Adjoint{<:Any,<:Abstrac
 end
 
 ### mul!
-mul!(C::StridedVecOrMat{T}, Q::AbstractQ{T}, B::StridedVecOrMat{T}) where {T} = lmul!(Q, copyto!(C, B))
+function mul!(C::StridedVecOrMat{T}, Q::AbstractQ{T}, B::StridedVecOrMat{T}) where {T}
+    require_one_based_indexing(C, B)
+    mB = size(B, 1)
+    mC = size(C, 1)
+    if mB < mC
+        inds = CartesianIndices(B)
+        copyto!(C, inds, B, inds)
+        C[CartesianIndices((mB+1:mC, axes(C, 2)))] .= zero(T)
+        return lmul!(Q, C)
+    else
+        return lmul!(Q, copyto!(C, B))
+    end
+end
 mul!(C::StridedVecOrMat{T}, A::StridedVecOrMat{T}, Q::AbstractQ{T}) where {T} = rmul!(copyto!(C, A), Q)
 mul!(C::StridedVecOrMat{T}, adjQ::Adjoint{<:Any,<:AbstractQ{T}}, B::StridedVecOrMat{T}) where {T} = lmul!(adjQ, copyto!(C, B))
 mul!(C::StridedVecOrMat{T}, A::StridedVecOrMat{T}, adjQ::Adjoint{<:Any,<:AbstractQ{T}}) where {T} = rmul!(copyto!(C, A), adjQ)

diff --git a/stdlib/LinearAlgebra/test/qr.jl b/stdlib/LinearAlgebra/test/qr.jl
@@ -180,8 +180,12 @@ rectangularQ(Q::LinearAlgebra.AbstractQ) = convert(Array, Q)
 
                 b = similar(a); rand!(b)
                 c = similar(a)
+                d = similar(a[:,1:n1])
                 @test mul!(c, q, b) ≈ q*b
+                @test mul!(d, q, r) ≈ q*r ≈ a[:,qrpa.p]
                 @test mul!(c, q', b) ≈ q'*b
+                @test mul!(d, q', a[:,qrpa.p])[1:n1,:] ≈ r
+                @test all(x -> abs(x) < ε*norm(a), d[n1+1:end,:])
                 @test mul!(c, b, q) ≈ b*q
                 @test mul!(c, b, q') ≈ b*q'
                 @test_throws DimensionMismatch mul!(Matrix{eltya}(I, n+1, n), q, b)
@@ -196,7 +200,10 @@ rectangularQ(Q::LinearAlgebra.AbstractQ) = convert(Array, Q)
                 @test_throws DimensionMismatch q * Matrix{Int8}(I, n+4, n+4)
 
                 @test mul!(c, q, b) ≈ q*b
+                @test mul!(d, q, r) ≈ a[:,1:n1]
                 @test mul!(c, q', b) ≈ q'*b
+                @test mul!(d, q', a[:,1:n1])[1:n1,:] ≈ r
+                @test all(x -> abs(x) < ε*norm(a), d[n1+1:end,:])
                 @test mul!(c, b, q) ≈ b*q
                 @test mul!(c, b, q') ≈ b*q'
                 @test_throws DimensionMismatch mul!(Matrix{eltya}(I, n+1, n), q, b)