Sebastien Loisel wrote:
This was my thinking as well, the the problem should be easy. By try the
code I supplied under matlab and see what you get for "det(A - lamba *
eye(n))".
for k=1:n foo(k)=det(B-ei(k)*eye(n)); end;
plot(foo);
for the complex matrices shows that the det is <= 10^-20.
Sébastien Loisel
Ok, I have to kill my sysadmin... It seems he only partially fixed the
-ffloat-store problem with atlas on my machine, as octave works fine for
the first matrix if I disable atlas... Could someone on fedora or debian
check
n=200;
A = spdiags([ones(n,1),4*ones(n,1),-ones(n,1)],[-2,0,2],n,n);
d0=eig(A);
merr=0.
for i=1:200
newerr = abs(det(A - d0(i)*eye(n)));
if (newerr > merr)
merr = newerr;
endif
endfor
printf("Max error: %g\n", merr);
and see that you get an error around 1e-20 and not 1e+200 like I do with
my atlas. I'd like to know if this atlas issue exists elsewhere, and if
not point my sysadmin to a distrib that has the right fix..