Keep improving fallbacks

Author: ChrisRackauckas

ext/LinearSolveSparseArraysExt.jl

@@ -72,13 +72,19 @@ const PREALLOCATED_UMFPACK = SparseArrays.UMFPACK.UmfpackLU(SparseMatrixCSC(0, 0
     Int[], Float64[]))
 
 function LinearSolve.init_cacheval(
-        alg::Union{LUFactorization, GenericLUFactorization}, A::AbstractSparseArray{<:Number, <:Integer}, b, u,
+        alg::Union{LUFactorization, QRFactorization, GenericLUFactorization}, A::AbstractSparseArray{<:Number, <:Integer}, b, u,
         Pl, Pr,
         maxiters::Int, abstol, reltol,
         verbose::Bool, assumptions::OperatorAssumptions)
     nothing
 end
 
+function init_cacheval(alg::QRFactorization, A::SparseMatrixCSC{Float64, Int}, b, u, Pl, Pr,
+        maxiters::Int, abstol, reltol, verbose::Bool,
+        assumptions::OperatorAssumptions)
+    ArrayInterface.qr_instance(convert(AbstractMatrix, A), alg.pivot)
+end
+
 function LinearSolve.init_cacheval(
         alg::UMFPACKFactorization, A::AbstractArray, b, u,
         Pl, Pr,