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Subspace Dimension.

In many cases it is useful to choose $p$ the dimension of the subspace larger than $\nev$ (the number of eigenvalues sought). In that case the slowest eigenvalue converges at a rate $\vert\lambda_{p+1}/\lambda_{\nev}\vert$ which may be significantly smaller than $\vert\lambda_{\nev+1}/\lambda_{\nev}\vert$. Practitioners in structural engineering have used choices like $p = \mbox{min} (2\nev,\nev+8)$; see [42].

Susan Blackford 2000-11-20