Re: About diagonal matrices

[John W. Eaton]

On 21-Feb-2009, Jaroslav Hajek wrote:

| Mathematically, there's no such thing as a NaN.

Substitute "numerically" for "mathematically" then, where
"numerically" means according to accepted conventions of the IEEE
standard for floating point arithmetic.

| In my opinion, the current behaviour is the most useful and sane and
| is OK if it's documented.
| If you intend to work on "fixing" these "issues", the please make the
| "mathematically wrong" behavior optional by a configuration variable,
| because I will most definitely want it to be set.

Yes, I understand that it is convenient for many uses for diagonal
and sparse matrices to have the properties you want.  But I'm also
don't like having things like

  full_matrix == diag_matrix

yet

  diag_matrix * scalar != full_matrix * scalar

for some values of scalar.

jwe