clear
format long
N=1000;
for ii=1:N
for jj=1:N
    A(ii,jj)=ii+(jj+1);
end
end
A=A+eye(N);
F(1:N,1)=1;
%det(A)
tic,X2=inv(A)*F;,toc
size(A)
tic,X=A\F;,toc
det(A)
tic,X3=cgs(A,F,1.e-9,N-1);,toc
