fix sparsify for dense matrices

Orb_AutFN.jl

@@ -34,7 +34,7 @@ immutable Settings
    tol::Float64
 end
 
-function sparsify!{T}(U::Array{T}, eps=eps(T))
+function sparsify{T}(U::Array{T}, eps=eps(T))
     n = rank(U)
     W = deepcopy(U)
     W[abs.(W) .< eps] = zero(T)
@@ -42,9 +42,9 @@ function sparsify!{T}(U::Array{T}, eps=eps(T))
         warn("Sparsification would decrease the rank!")
         W = U
     end
-    U = sparse(U)
-    dropzeros!(U)
-    return U
+    W = sparse(W)
+    dropzeros!(W)
+    return W
 end
 
 function sparsify!{T}(U::SparseMatrixCSC{T}, eps=eps(T))
@@ -53,8 +53,6 @@ function sparsify!{T}(U::SparseMatrixCSC{T}, eps=eps(T))
     return U
 end
 
-sparsify{T}(U::AbstractArray{T}, eps=eps(T)) = sparsify!(deepcopy(U), eps)
-
 small_to_zero!{T}(A::AbstractArray{T}, eps=eps(T)) = A[abs(A) .< eps] = zero(T)
 
 function init_model(Uπs)