Missing sparse methods

It seems like there are missing sparse matrix methods. In both 1.0.2 and 0.7 this code:

using SparseArrays
using LinearAlgebra

A = sprand(10,10,.9)
b_dense = Array(sprand(10,1,.8)) # works
b_sparse = sprand(10,1,.8) # doesn't work
x = A\b_dense # works
x = A\b_sparse # doesn't work
lu!(A) # gives an error

produces these errors:
julia> x = A\b_sparse # error ERROR: MethodError: no method matching ldiv!(::SuiteSparse.UMFPACK.UmfpackLU{Float64,Int64}, ::SparseMatrixCSC{Float64,Int64})
ERROR: MethodError: no method matching lu!(::SparseMatrixCSC{Float64,Int64})

We use the library UMFPACK for solving problems with an asymmetric lhs and unfortunately the library doesn’t support a sparse rhs.


That makes sense, but it seems like the error message could be a bit more user friendly.

Also, why does lu!(A) not work for a sparse matrix? The existing error for A\b pointed me to lu!, but lu!() doesn’t work. It seems odd that we can’t factor sparse matrices using the “default” version of lu.

You should use lu(A). lu!(A) means that you want LU factorization in-place, which is not generally possible for sparse matrices.


A post was split to a new topic: Sparse solve with sparse rhs