Re: sc_vector proposal

For HLS we do support synthesis of user defined classes, with the usual limitations, so it is not correct to assume if it is user defined there is no issue to worry about HLS.

That said I have not looked into the details of sc_vector

Mac

----- Original Message -----
From: owner-systemc-p1666-technical@eda.org <owner-systemc-p1666-technical@eda.org>
To: Philipp A. Hartmann <philipp.hartmann@offis.de>
Cc: john.aynsley@doulos.com <john.aynsley@doulos.com>; P1666 Technical WG <systemc-p1666-technical@eda.org>
Sent: Fri Nov 05 10:32:22 2010
Subject: RE: sc_vector proposal

Philipp, all,

comments below.

-----Original Message-----
From: Philipp A. Hartmann [mailto:philipp.hartmann@offis.de]
Sent: Thursday, November 04, 2010 10:57 PM
To: Jerome CORNET
Cc: john.aynsley@doulos.com; P1666 Technical WG
Subject: Re: sc_vector proposal

> Since there seems to be consensus that we should not add extra levels
> in the hierarchy, I would propose to use another function name for this,
> since the elements are not "child objects" in the strict sense. Maybe
> 'get_elements' would be better?

> Shall we restrict the sc_view() technique to such (member) objects as
> well? This could keep the symmetry in the interface of sc_vector<T> and
> a corresponding sc_vector_view<T, & T::Member > by adding a
> 'get_elements' there as well.

Ok with that.

> I'm fine with creating vectors during simulation (if the elements
> support it). But I would prefer to tie the lifetime of the elements to
> the lifetime of the vector itself, and thus not supporting the dynamic
> expansion (or shrinking) of the vector.

> Having dynamically resizable vectors would require all kinds of
> dynamic checks during simulation and hamper the support of sc_vector for
> HLS tools. Init-only vectors can be supported by such tools quite
> easily (at least without custom Creator functors).

I don't fundamentally disagree with you on this, but I have some remarks.

- Not supporting vector's shrinking seems indeed simpler to avoid problems of
object lifetime.

- However, I don't see why we shouldn't support adding elements during the simulation
as:
   - This would by definition be only possible for user-derived sc_object (and not for sc_port/sc_module)
Therefore, this would have not much effects on HLS support, as HLS will focus on well-known sc_object(s) and not
user-defined classes (I guess).
   - There is no relation between expansion of the vector and object's lifetime since technically
the internal vector storage is holding object pointers (and this is transparent for the user).

Anyway, I have no strong motivation/use cases for requiring the vector expansion feature, so I am ok
to forbid it if necessary.

Jerome

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