[Dune-devel] [Dune-Bugs] [#1041] BCRSMatrix does not always initialize data memory

[Markus Blatt]

Hi Oliver,

On Tue, Jan 22, 2013 at 09:58:19AM +0100, Oliver Sander wrote:
> But let me ask again: why the need for  MatrixHasTrivialConstructor?
> Does it really make a measurable difference to omit the empty
> default constructors in BCRSMatrix?

I do not know, but I am pretty sure that it is not slower. Sure one could
rely on the compiler optimization, but why depend on it if we can do
it ourselves.

> And if it does matter: shouldn't we use std::is_pod instead of the
> hand-coded MatrixHasTrivialConstructor?

I doubt that FieldMatrix can be regarded as a plain old datatype. 
Quoting cplusplus.com: "A POD type (which stands for Plain Old Data
type) is a type whose characteristics are supported by a data type in
the C language, either cv-qualified or not."

Cheers,

Markus