The 'independent' extended Metropolis sampler, in which each proposed model is independant of the previously visited model, can be chosen by forcing the 'step'-length to be 1 (i.e. leading to independant samples from the prior), using e.g.

% force independent prior sampling
for ip=1:length(prior);
	prior{ip}.seq_gibbs.step=1;
	prior{ip}.seq_gibbs.i_update_step_max=0;
end
% run 'independent' extended Metropolis sampling
[options,data,prior,forward,m_current]=sippi_metropolis(data,prior,forward,options)