Commit 8f2bbb8d authored by Tim Mitchell's avatar Tim Mitchell
Browse files

eigsPlus help doc wordsmithing

parent 24305294
......@@ -14,28 +14,29 @@ function varargout = eigsPlus(varargin)
% will return the eigenvalues as a diagonal matrix when
% eigenvectors are always requested.
%
% 3) If no eigenvalues are resolved, R2016b and earlier would throw
% an error. On these versions, eigsPlus will instead throw a
% warning. On R2017a, eigs also adopted the same convention of
% throwing a warning instead of an error. However, on R2017b,
% eigs no longer throws a warning or an error. To maintain
% consistency, as of R2017b, eigsPlus also no longer throws a
% warning. Recall in the case that no Ritz value converges, the
% returned eigenvalues and eigenvectors will respectively be an
% empty vector and an empty matrix.
% 3) If no eigenvalues are resolved, on R2016b and earlier, eigs
% would throw an error; on these versions, eigsPlus will instead
% throw a warning. On R2017a, eigs also adopted the same
% convention of throwing a warning instead of an error. However,
% on R2017b, eigs no longer throws a warning or an error. To
% maintain consistency, as of R2017b, eigsPlus also no longer
% throws a warning. Recall in the case that no Ritz value
% converges, the returned eigenvalues and eigenvectors will be
% empty.
%
% 4) The number of iterations incurred is returned via the third
% output argument. Flag is no longer returned as the user can
% always equivalently check if the number of eigenvalues returned
% is less than what the user requested. For R2017a and earlier,
% this is the number of ARPACK iterations. On newer releases,
% this is the number of Krylov Schur iterations but note that for
% problems with symmetric positive definite B matrices using
% shift-invert, the Krylov Schur method may be restarted once, if
% the first fails; in this case, the number of iterations is the
% sum of two attempts.
%
% 5) R2017a and earlier only: The user may set opts.isreal to false
% 4) The third output argument, flag, has been repurposed to return
% the number of iterations that is incurred; the user can always
% equivalently check if the number of eigenvalues returned is
% less than what the user requested by checking the dimensions of
% the eigenvalue and/or eigenvector output arguments. For R2017a
% and earlier, this is the number of ARPACK iterations. On newer
% releases, this is the number of Krylov Schur iterations but
% note that for problems with symmetric positive definite B
% matrices using shift-invert, the Krylov Schur method may be
% restarted once, if the first fails; in this case, the number of
% iterations is the sum of two attempts.
%
% 5) R2017a and earlier only: the user may set opts.isreal to false
% to force the complex ARPACK routines to be used even if matrix
% A is real and opts.v0 is either real or complex (whereas
% Matlabs's eigs would throw an error in these cases). eigsPlus
......
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