Re: [eigen] Malloc-free dynamic matrices

[leon zadorin <leonleon77@xxxxxxxxx>]

On 3/3/10, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> 2010/3/2 Márton Danóczy <marton78@xxxxxxxxx>:
[...]
>> The only API changes are a new option NeverRealloc (the name is maybe
>> not the best) and a method reserve(int size) that allocates the
>> memory. Then, a Matrix<Scalar, Dynamic, Dynamic, NeverRealloc> keeps
>> track of its allocated size via the member variable m_size and each
>> mat.resize(rows, cols) only changes two ints instead of actually
>> allocating memory. If rows*cols < m_size, an assertion error is
>> raised.

[...]

> approach... my main concern right now is that it's touching and
> complexifying a few very central places in Eigen, whereas the use case
> is very special. For that reason I wonder if this should rather be
> implemented as a new separate variant of the Matrix class itself...

And if it is a special/rare case usage, would it not be possible to
already achieve this behavior with a custom pre-allocated block of
memory and then instead of using matrix type simply using the
object(s) of Map<> type?

The "mapped" matricies would not need explicit resizing in the first
place... and reserving of the max size is simply done at allocation of
the very original memory slab -- as per current API and it's
capabilities?

I suppose an adapter pattern may be deployed to create custom class --
but it's internals would/could still rely on the Map<> semantics...

Kind regards
Leon.