Date: 2001-12-02 04:39:35
--- In boost_at_y..., Peter Schmitteckert (boost) <boost_at_s...> wrote:
> > > I'd prefer the diagonal elements of a complex hermitean
> > > matrix to be real. Or at least to have a function
> > > returning the diagonal elements as real values.
> > How would you design the corresponding iterator interface using
> > diagonal elements? Shouldn't we better assert, that imag (m [i]
> > == 0? I'll think about an special accessor for diagonal elements.
> In my own matrix package I did the following:
> 1) a special function that return diagonal elements, e.g. return
> double for complex<double>
> 2) the element access through
> F& HermitianMatrix::operator(const i, const j)
> is only defined for i<j
I'm rather sure, that we should try to go with double d = real (hm
(i, i)). Isn't that similar enough to double d = hm.diag (i)? There
also is an open issue with proxies like diag, which I'll address in
> but I had no iterators defined :(, so I think a special accessor
> for diagonal elements is the way to go.
> > > -> In the same spirit one should not be allowed to
> > > multiply a complex hermitean matrix with a non-real
> > > scalar, or at least this shouldn't return a hermitean matrix.
> > The most critical part here is hermitean_matrix *= scalar. Again
> > prefer to assert that imag (scalar) == 0.
> But that's sensitive to rounding problems, e.g. if you're writing
> system solver you might create minimal imaginary parts, and you have
> to set the explicitly to zero.
The type of the scalar in hermitean_matrix *= scalar is a template
argument. So it should be no problem to write hm *= d;
> > I imagine, that deriving banded_hermitean_matrix (or
> > hermitean_banded_matrix :-) statically from matrix_expression
> > give you the neccessary ET support.
> > A hint: may be you better try to implement a somewhat simpler form
> > like skew_hermitean_matrix ;-) first.
> > Thanks for your feedback.
> o.k., maybe you're right,
> would you be willing to audit/comment my attempts to implement
> new matrix types ?
Yes (although we're losing one of our rare users ;-).
P.S.: Did you consider to use hermitean_adaptor<banded_matrix<> >?
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