Re: sc_event naming: Cadence position on proposed extension

John,

A lot of nice words from Bishnupriya, but the only objection against our extension
proposal is hierarchical naming of objects, which is not part of our proposal, and
for good reason.

But does this mean that we should do a lousy job on hierarchical event naming?
Or, put differently, should we treat events as first class citizens or not?

Let's take a look at the current objects types. We have modules and processes,
which are the most important object types when modeling and simulating with
SystemC. Their hierarchical name is just perfect, and also in other regards we
can say that these object types are indeed first class citizens. The other object
types, such as ports, exports, primitive channels, are already in the "poor objects"
(or second class citizens) category.

Enter named events. We already decided not to make them objects, but to
treat them somehow like objects. In which of the two above categories (first
class citizens or second class citizens) do events belong? Bishnupriya is
saying that we should put them with the second class citizens, and do as
poor a job at naming them. But events _are_ first class citizens that belong
with modules and processes. During simulation processes and events are
at center stage.

So my question is: why not treat events as we do modules and processes?

An implementation that has been out there for 2 years, on its own, cannot be
enough reason for unamended standardization.

-Martin

On 2010-11-22 11:35, Bishnupriya Bhattacharya wrote:
> John, All,
> Over the past few days, within Cadence, we have carefully reviewed the SNPS extension to the Cadence event naming
> proposal. Our position is as below. There is strong agreement within Cadence on this position, including from Stuart .
> First, about allowing objects to parent other objects, there are certainly issues (as several of you have pointed out)
> if we try for an ambitious scheme to arbitrarily change the object hierarchyat run-time. However, that is not our
> intent. We're trying to explore if we can carve out a small subset that will be useful.We're not envisaging a dynamic
> module hierarchy. Any object hierarchy changes will be restricted to elaboration time only.
> So, what is the motivation? One thing that comes to mind is a natural grouping of things to better express the intent
> of a class, and prevent "leakage" of internal implementation objects to the outside of this class.
> Consider an aggregate class like the TLM2 simple_target_socket. It has a number of other objects and events inside it
> - these are all internal implementation artifacts of this socket. Today all of these internal objects/events end up in
> the parent module's scope. The output of get_child_objects() and get_child_events() on a target module that owns a
> simple_target_socket is given below.
> top.target.socket
> top.target.socket_port_0
> top.target.m_peq_0
> top.target.b2nb_thread_0
> top.target.peq_with_cb_and_phase_0
> top.target.fec_0
> top.target.event_0
> top.target.event_1
> top.target.event_2
> top.target.event_3
> Everything besides the target socket itself, does not really belong to the parent module's scope; the rest is useless
> clutter that a user never wants to see. It is safe to say that the simple_target_socket class does not intentionally
> want to expose these internal implementation artifacts, but today it has no choice but to do so. With the SNPS
> extension proposal, the events will now go out of this list - the poor objects will be left behind
> top.target.socket
> top.target.socket_port_0
> top.target.m_peq_0
> top.target.b2nb_thread_0
> top.target.peq_with_cb_and_phase_0
> top.target.fec_0
> This is not consistent. It does not feel right that events will end up with the property that they can be grouped more
> hierarchically, but objects can't. As things stand today (or rather I should say with the Cadence proposal), things
> are not perfect, but at least an user can expect consistency when constructing an user-defined object wrt scope of
> internal objects and events. With the SNPS extension, that is no longer true. Itis as if events have become more of a
> first class citizen than objects.
> We all agree that a proper "fix" for this - such that objects can also be children of other objects in some
> restricted, but useful fashion - is not simple. Many issues need to be considered, especially wrt adjusting existing
> object's ctor, and other issues that Philip has raised. Realistically speaking there isn't time in this round to
> consider all the ramifications, and arrive at a solution (or conclude one is not possible).
> Given that, we feel it will be inappropriate to only standardize the object-owning-events feature, and leave things in
> a half-baked state. We do not buy the argument that since this feature pertains to event naming it will make it to
> this round - we DO need to consider the ramifications of proposed solutions to the rest of the ecosystem. We feel it
> is more appropriate for the LRM to leave kernel event naming as implementation-defined in this round, and include this
> feature as an addition in the next round if it is so deemed. We're opposed to rushing something into the LRM that
> leaves things in an inconsistent state without having the time to consider the complete problem.
> Leaving this aspect implementation-defined in p1666-2010 allows each vendor (including the OSCI ref sim) to experiment
> with developing a sane object/event naming and parent/child relationship hierarchy while remaining compliant with the
> 2010 standard.In 1666-2012 (or whenever the next round is) we can then propose standardizing that which we have
> previously implemented and tested.
> We would like to hear what others have to say on this topic.
> Thanks,
> -Bishnupriya
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------
> *Bishnupriya Bhattacharya* | Software Architect - Virtual System Platform | Cadence
> P: +91.80.4184.1197 www.cadence.com <http://www.cadence.com/>
> ----------------------------------------------------------------------------------------------------------------------------------------------------
>
>
>
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