%%************************************************************************
%% NTcorr: corrector step for the NT direction.
%%
%% SDPT3: version 3.1
%% Copyright (c) 1997 by
%% K.C. Toh, M.J. Todd, R.H. Tutuncu
%% Last Modified: 16 Sep 2004
%%************************************************************************

function [dX,dy,dZ] = NTcorr(blk,At,par,rp,Rd,sigmu,hRd,...
    dX,dZ,coeff,L,X,Z)

global matfct_options solve_ok

printlevel = par.printlevel;
%%
[rhs,EinvRc] = NTrhsfun(blk,At,par,X,Z,rp,Rd,sigmu,hRd,dX,dZ);
m = length(rp); ncolU = size(coeff.mat12,2);
rhs = [rhs; zeros(m+ncolU-length(rhs),1)];
%%
if strcmp(matfct_options,'chol') || strcmp(matfct_options,'spchol') ...
        || strcmp(matfct_options,'ldl') || strcmp(matfct_options,'spldl')
    [xx,resnrm,solve_ok] = symqmr(coeff,rhs,L,[],[],printlevel);
    if (solve_ok<=0) && (printlevel)
        fprintf('\n  warning: symqmr fails: %3.1f.',solve_ok);
    end
else
    [xx,resnrm,solve_ok] = mybicgstab(coeff,rhs,L,[],[],printlevel);
    if (solve_ok<=0) && (printlevel)
        fprintf('\n  warning: bicgstab fails: %3.1f.',solve_ok);
    end
end
if (printlevel>=3); fprintf('%2.0d ',length(resnrm)-1); end
%%
[dX,dy,dZ] = NTdirfun(blk,At,par,Rd,EinvRc,xx,m);
%%************************************************************************


