diff --git a/src/contractions/site.jl b/src/contractions/site.jl
index 68c495f..5aadbd5 100644
--- a/src/contractions/site.jl
+++ b/src/contractions/site.jl
@@ -170,6 +170,15 @@ function contract_tensors43(M::SiteTensor{R,4}, B::Tensor{R,3}) where {R<:Real}
     @inbounds Bp = B[:, :, p4] .* reshape(M.loc_exp, 1, 1, :)
     @cast Bp[(x, y), z] := Bp[x, y, z]
     ip123 = SparseCSC(R, M.lp, M.projs[1], M.projs[2], M.projs[3], device)
+    @show nnz(ip123)
+    @show size(ip123)
+    @show size(Bp)
+    @show size(Bp')
+    @show typeof(Bp)
+    @show typeof(ip123)
+    @show typeof(Bp')
+    @show (sm1, sm2, sm3, sb1, sb2)
+    @show size(ip123 * Bp')
     out = reshape(ip123 * Bp', sm1, sm2, sm3, sb1, sb2)
     out = permutedims(out, (4, 1, 5, 3, 2))
     reshape(out, sb1 * sm1, sb2 * sm3, sm2)
diff --git a/src/contractions/sparse.jl b/src/contractions/sparse.jl
index a20af83..fc58547 100644
--- a/src/contractions/sparse.jl
+++ b/src/contractions/sparse.jl
@@ -12,7 +12,7 @@ end
 # TODO shouldn't we have CSR format instead?
 function SparseCSC(::Type{R}, p::CuArray{Int64,1}; mp = nothing) where {R<:Real}
     n = length(p)
-    if mp == nothing
+    if isnothing(mp)
         mp = maximum(p)
     end
     cn = CuArray(1:n+1)  # aux_cusparse(R, n)
@@ -22,7 +22,7 @@ end
 
 function SparseCSC(::Type{R}, p::Vector{Int64}; mp = nothing) where {R<:Real}
     n = length(p)
-    if mp == nothing
+    if isnothing(mp)
         mp = maximum(p)
     end
     cn = collect(1:n)
diff --git a/src/transfer.jl b/src/transfer.jl
index 7fcac54..994266e 100644
--- a/src/transfer.jl
+++ b/src/transfer.jl
@@ -69,7 +69,7 @@ end
 
 
 
-which_device(ten::Nothing) = Set()
+which_device(::Nothing) = Set()
 which_device(ψ::Union{QMpo{T},QMps{T}}) where {T} =
     union(which_device.(values(ψ.tensors))...)
 which_device(ten::MpoTensor) =