missingness sum benchmark

gistfile1.jl

immutable CheapMulBool
    x::Bool
end
immutable Negated{T}
     x::T
end
immutable BitWrapper
     x::Vector{Uint64}
end
Base.getindex(x::BitWrapper, i) = CheapMulBool(!Base.unsafe_bitgetindex(x.x, i))
Base.getindex(x::Negated, i) = CheapMulBool(unsafe_load(convert(Ptr{Uint8}, pointer(x.x)), i) == 0)
*(x::CheapMulBool, y::Number) = ifelse(x.x, y, zero(y))

function f(x, y)
    z = zero(eltype(x))
    @simd for i = 1:length(x)
       @inbounds z += y[i]*x[i]
    end
    z
end

x = randn(10000000)
ybool = rand(Bool, length(x))
ybit = bitpack(ybool)
yfloat = convert(Vector{Float64}, !ybool)
f(x, Negated(ybool))
f(x, BitWrapper(ybit.chunks))
f(x, yfloat)
@time for i = 1:50 f(x, Negated(ybool)) end
@time for i = 1:50 f(x, BitWrapper(ybit.chunks)) end
@time for i = 1:50 f(x, yfloat) end

The comparison is to LLVM 3.3, which partially vectorizes the loop whereas LLVM SVN doesn't vectorize it at all. I can't explain why.