Slow `==`

[putianyi889]

falls back to dense comparison

julia> A = brand(100,100,0,0);

julia> @btime A==A
  25.000 μs (0 allocations: 0 bytes)
true

julia> A = brand(1000,1000,0,0);

julia> @btime A==A
  2.409 ms (0 allocations: 0 bytes)
true