proximal_entropy

xrayvision.mem.proximal_entropy(y, m, lamba, Lip, tol=1e-10)

This function computes the value of the proximity operator of the entropy function subject to positivity constraint, i.e. it solves the problem

argmin_x 1/2*|| y-x ||^2 + lambda/Lip * H(x) subject to x >= 0

Actually, this problem can be reduced to finding the zero of the gradient of the objective function and it is therefore solved by means of a bisection method.

Parameters:

• y

• m

• lamba

• Lip

• tol