Re: Computing 22k x 22k matrix eigen values

exact arithmetic? you mean indeed integer arithmetic,
then computing the eigenvalues of the tridiagonal matrix numerically?
special version avoiding the normalization
o.k.
but what about the eigenvectors..
i still hope he wants only some ..


Yes, exact integer arithmetic with 2^n scalings. Matrix known only
as product Ax. Nonzero entries (actually -1,+1) about 100/row.
Picture perfect for Lanczos if reorthogonalization is skipped
hence exact arithmetic. Tridiag converted to quad float when done,
all 16M eigenvalues extracted. No eigenvectors needed, I think.

.

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