function td = comvkomb(K,m,n)
% try to express K as a conv. comb of other elements
% of [-1,1]^(m^n)

iip = find(K>0);
e1 = min(K(iip));
e2 = min(1-K(iip));
e = min(e1,e2);

i1 = iip(1);
i2 = iip(2);

K0 = K;
v0 = Psi(K0,m,n);

% WANT:
% (i) Psi(K1), Psi(K2) <= v0
% (ii) K0 = (K1+K2)/2

d1=e; d2=e;

while 1
    
K1 = K0;
K1(i1) = K1(i1) + d1;
%x = binsearch(K1,i2,v0,m,n);
%d = K1(i2) - x;
K1(i2) = K1(i2) - d2;
%if d > e
%    e = e/2;
%else
%    break
%end
%end

K2 = K0;
K2(i1) = K2(i1) - d1;
K2(i2) = K2(i2) + d2;

% (ii) is ensured automatically

v1 = Psi(K1,m,n);
v2 = Psi(K2,m,n);
g = ((v1<=v0) & (v2<=v0));
if g
    break
else
    if (v1 > v0)
        d1 = d1/2;
    end
    if (v2 > v0)
        d2 = d2/2;
    end
end
end
totdif((K1+K2)/2,K0);
return

function x = binsearch(K,i,v,m,n)
lowx = 0;
higx = 1;
tol = 1e-8;
while higx - lowx > tol
    x = (lowx + higx)/2;
    K(i) = x;
    vx = Psi(K,m,n);
    if vx < v
        % too small; make x bigger
        lowx = x;
    else
        % too bix; make x smaller
        higx = x;
    end
end
return