calc_RtR_prior

 RtR = calc_RtR_prior( inv_model )
 CALC_RtR_PRIOR: calculate image regularization prior
   R'*R (which is an estimate of the inverse of the covariance)

   Typically, the image prior is matrix n_elem x n_elem of the
   normalized a priori crosscorrelation FEM element values
 
 calc_RtR_prior can be called as
    RtR_prior= calc_RtR_prior( inv_model, ... )

 and will call the function inv_model.RtR_prior
 parameters to RtR_prior should be passed in the field
 inv_model.RtR_prior_function_name.parameters

 if there exists a field inv_model.rec_model, then
   the prior is calculated on the rec_model rather than
   the fwd_model. This will not be done if 
 inv_model.prior_use_fwd_not_rec= 1;

 RtR_prior    the calculated RtR regularization prior
 inv_model    is an inv_model structure

 If a function to calculate RtR_prior is not provided,
 RtR = R_prior' * R_prior;

0001 function RtR_prior = calc_RtR_prior( inv_model )
0002 % RtR = calc_RtR_prior( inv_model )
0003 % CALC_RtR_PRIOR: calculate image regularization prior
0004 %   R'*R (which is an estimate of the inverse of the covariance)
0005 %
0006 %   Typically, the image prior is matrix n_elem x n_elem of the
0007 %   normalized a priori crosscorrelation FEM element values
0008 %
0009 % calc_RtR_prior can be called as
0010 %    RtR_prior= calc_RtR_prior( inv_model, ... )
0011 %
0012 % and will call the function inv_model.RtR_prior
0013 % parameters to RtR_prior should be passed in the field
0014 % inv_model.RtR_prior_function_name.parameters
0015 %
0016 % if there exists a field inv_model.rec_model, then
0017 %   the prior is calculated on the rec_model rather than
0018 %   the fwd_model. This will not be done if
0019 % inv_model.prior_use_fwd_not_rec= 1;
0020 %
0021 % RtR_prior    the calculated RtR regularization prior
0022 % inv_model    is an inv_model structure
0023 %
0024 % If a function to calculate RtR_prior is not provided,
0025 % RtR = R_prior' * R_prior;
0026 
0027 % (C) 2005-2008 Andy Adler. License: GPL version 2 or version 3
0028 % $Id: calc_RtR_prior.html 2819 2011-09-07 16:43:11Z aadler $
0029 
0030 inv_model = rec_or_fwd_model( inv_model);
0031 
0032 RtR_prior = eidors_obj('get-cache', inv_model, 'RtR_prior');
0033 if ~isempty(RtR_prior)
0034    eidors_msg('calc_RtR_prior: using cached value', 3);
0035    return
0036 end
0037 
0038 if isfield(inv_model,'RtR_prior')
0039    RtR_prior= feval( inv_model.RtR_prior, inv_model );
0040 elseif isfield(inv_model,'R_prior')
0041    % The user has provided an R prior. We can use this to
0042    % calculate RtR= R'*R;
0043    R= feval( inv_model.R_prior, inv_model );
0044 
0045    RtR_prior = R'*R;
0046 else
0047    error('calc_RtR_prior: neither R_prior or RtR_prior func provided');
0048 end
0049 
0050 if isfield(inv_model.fwd_model,'coarse2fine')
0051    c2f= inv_model.fwd_model.coarse2fine;
0052    if size(RtR_prior,1)==size(c2f,1)
0053 %     we need to take into account coarse2fine - using a reasonable tol
0054       eidors_msg('calc_RtR_prior: using coarse2fine to model RtR');
0055       f2c= c2f'; %pinv(c2f,1e-6);
0056       RtR_prior=c2f'*RtR_prior*c2f;
0057    end
0058 end
0059 
0060 eidors_obj('set-cache', inv_model, 'RtR_prior', RtR_prior);
0061 eidors_msg('calc_RtR_prior: setting cached value', 3);
0062 
0063 function inv_model = rec_or_fwd_model( inv_model);
0064 
0065    if isfield(inv_model,'rec_model');
0066       use_rec_model = 1;
0067       try if inv_model.prior_use_fwd_not_rec== 1;
0068          use_rec_model = 0;
0069       end; end
0070 
0071       if use_rec_model
0072          inv_model.fwd_model= inv_model.rec_model;
0073          inv_model= rmfield(inv_model,'rec_model');
0074       end
0075    end