1oly

function gp(nnls::Function,A::AbstractMatrix,b::AbstractVector,x0::AbstractVector,maxit::Integer)
	obj = zeros(maxit)
	x = x0
	for i = 1:maxit
		f,g,r = nnls(A,b,x)
		g[(x.==0.0) & (g.>0.0)] = 0.0
		alpha = dot(A*g,r)/dot(A*g,A*g)
		x = x-alpha*g
		x[x.<0.0] = 0.0
		obj[i] = f

1oly

function func(b,x,Fps)
    r = fftshift(ifft(fft(x).*Fps)) - b;
    return r
end