%% [g,gp] = snr(p,H);%% calculates snr and grad of snr (if asked), in g and gp%% H(i,j)  - fading between source of link <i> and dst of link <j>% p(i)    - power allocated to link <i>%% g(i)    - SNR at reception of link <i>% gp(i,j) - gradient dg(i)/dp(j)%function [g,gp]=snr(p, H)N = size(p,1);g = zeros(N,1);for i=1:N    I = 1 + H(i,:)*p - H(i,i)*p(i);    g(i) = H(i,i)*p(i) / I;endif nargout > 1    gp = zeros(N,N);    for i=1:N        I = 1 + H(i,:)*p - H(i,i)*p(i);        for j=1:N;            if i == j                gp(i,j) = H(i,i) / I;            else                gp(i,j) = - H(i,j) * H(i,i)*p(i) / I^2;            end        end    endend