Hi everyone,

I am very new to Julia, so please let me know if there is info in the documentation that would have avoided the issue. I use the following version:

```
Julia Version 0.6.1
Commit 0d7248e (2017-10-24 22:15 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin14.5.0)
CPU: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Sandybridge)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, ivybridge)
```

and get the following error (minimal working example below):

```
ERROR: LoadError: MethodError: no method matching lufact!(::Hermitian{Float64,SparseMatrixCSC{Float64,Int32}}, ::Type{Val{true}})
```

which is due to the sparse matrix using Int32 for indexing. If the indices are Int64 everything works just fine. I donâ€™t know if this is a bug or wanted behavior. However, the error message didnâ€™t help me much and I needed quite some time to figure the issue out. I didnâ€™t open an issue on github, because I wasnâ€™t sure if it is appropriate.

Cheers,

Lukas

### Code

```
# Setup (indices, values and r.h.s.)
i1 = [1, 2, 3, 2, 1]
j1 = [1, 2, 3, 1, 2]
i2 = convert(Array{Int32, 1}, i1)
j2 = convert(Array{Int32, 1}, j1)
v = [1.0, 2.0, 3.0, 0.5, 0.5]
b = [1.0, 2.0, 3.0]
# Working Version
A = sparse(i1, j1, v)
println("A has type: ", typeof(A))
x = A \ b
println("x = ", x)
# Non-Working version
A2 = sparse(i2, j2, v)
println("A2 has type: ", typeof(A2))
x2 = A2 \ b
println("x2 = ", x2)
```

### Full Output:

A has type: SparseMatrixCSC{Float64,Int64}

x = [0.571429, 0.857143, 1.0]

A2 has type: SparseMatrixCSC{Float64,Int32}

ERROR: LoadError: MethodError: no method matching lufact!(::Hermitian{Float64,SparseMatrixCSC{Float64,Int32}}, ::Type{Val{true}})

Closest candidates are:

lufact!(!Matched::Union{Base.ReshapedArray{T<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64},2,A,MI} where MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N} where N} where A<:Union{DenseArray, SubArray{T,N,P,I,true} where I<:Tuple{Union{Base.Slice, UnitRange},Vararg{Any,N} where N} where P where N where T}, DenseArray{T<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64},2}, SubArray{T<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64},2,A,I,L} where L} where I<:Tuple{Vararg{Union{Base.AbstractCartesianIndex, Int64, Range{Int64}},N} where N} where A<:Union{Base.ReshapedArray{T,N,A,MI} where MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N} where N} where A<:Union{DenseArray, SubArray{T,N,P,I,true} where I<:Tuple{Union{Base.Slice, UnitRange},Vararg{Any,N} where N} where P where N where T} where N where T, DenseArray}, ::Union{Type{Val{false}}, Type{Val{true}}}) where T<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64} at linalg/lu.jl:16

lufact!(!Matched::Union{Base.ReshapedArray{T,2,A,MI} where MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N} where N} where A<:Union{DenseArray, SubArray{T,N,P,I,true} where I<:Tuple{Union{Base.Slice, UnitRange},Vararg{Any,N} where N} where P where N where T}, DenseArray{T,2}, SubArray{T,2,A,I,L} where L} where I<:Tuple{Vararg{Union{Base.AbstractCartesianIndex, Int64, Range{Int64}},N} where N} where A<:Union{Base.ReshapedArray{T,N,A,MI} where MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N} where N} where A<:Union{DenseArray, SubArray{T,N,P,I,true} where I<:Tuple{Union{Base.Slice, UnitRange},Vararg{Any,N} where N} where P where N where T} where N where T, DenseArray} where T, ::Union{Type{Val{false}}, Type{Val{true}}}) at linalg/lu.jl:31

lufact!(!Matched::Tridiagonal{T}, ::Union{Type{Val{false}}, Type{Val{true}}}) where T at linalg/lu.jl:321

Stacktrace:

[1] (::Hermitian{Float64,SparseMatrixCSC{Float64,Int32}}, ::Array{Float64,1}) at ./linalg/generic.jl:832

[2] (::SparseMatrixCSC{Float64,Int32}, ::Array{Float64,1}) at ./sparse/linalg.jl:869

[3] include_from_node1(::String) at ./loading.jl:576

[4] include(::String) at ./sysimg.jl:14

[5] process_options(::Base.JLOptions) at ./client.jl:305

[6] _start() at ./client.jl:371

while loading /Users/[private]/sparse_bug_example.jl, in expression starting on line 20