Add singularity check for robust LU factorization

Author: AkhilAkkapelli

src/array/lu.jl

@@ -36,6 +36,8 @@ end
 
 function update_ipiv!(ipivl::AbstractVector{Int}, piv_idx::AbstractVector{Int}, piv_val::AbstractVector{T}, k::Int, nb::Int) where T
     max_piv_idx = argmax(abs.(piv_val))
+    max_piv_val = abs(piv_val[max_piv_idx])
+    isapprox(max_piv_val, zero(T); atol=eps(T)) && throw(SingularException(k))
     ipivl[1] = (max_piv_idx+k-2)*nb +  piv_idx[max_piv_idx]
 end