function [B,i] = diagdom (A,tol)
% DIAGDOM
%
%     [B, i] = diagdom (A, tol)
%
% DIAGDOM returns a diagonally dominant matrix B by modifying the
% diagonal of A.  If row i violates diagonal dominance, then A(i,i) is
% modified by setting it so that its absolute value is (1+tol)*f, where
% f is the sum of the absolute values of the off-diagonal entries in row i
% (assuming f is large enough).  If f is smaller than tol, then the absolute
% value of A(i,i) is set to (1+tol)*tol.  The sign of A(i,i) is preserved.
% The input argument tol is optional; if not present, a default value of
% 100*eps is used.  The outputs are B (the modified matrix) and a vector i
% that contains a list of the row indices of the rows that violated
% diagonal dominance.
%
% MATLAB Primer, 6th Edition
% Kermit Sigmon and Timothy A. Davis
% Section 9.5, page 53.
%
error ('diagdom mexFunction not found') ;