RE: [sv-ac] reminder to vote on mantis 1550

I think that values assigned in initial blocks should not be used as the
sampled value. that assignment happens at time 0+.  The default or
declaration assigned value should be used.

ed
 

> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On 
> Behalf Of Doron Bustan
> Sent: Thursday, January 25, 2007 9:40 AM
> To: Miller Hillel-R53776
> Cc: Havlicek John-r8aaau; sv-ac@eda-stds.org
> Subject: Re: [sv-ac] reminder to vote on mantis 1550
> 
> That rise another issue that I was not aware of.
> Since assertions use sampled values, it means that on time 0
> they use the default variables values, even if they are assigned
> to different values in initial blocks. Is that what we want?
> 
> Doron
> 
> Miller Hillel-R53776 wrote:
> 
> >John,
> >
> >I am not sure we should make such an inconsistency it sounds 
> troubling.
> >
> >However, the reason why static variable declarartion 
> assignments cannot
> >be used, is that it cannot be used by an outer module reference. If I
> >want to influence the initial value of a $ function that is 
> dependent on
> >a module's reg, how would this be done. Would I need to 
> rewrite the code
> >with the declaration assignment?
> >
> >Maybe we need an additional construct for initializing the $sampled
> >value of a variable at the same time as assignment declaration.
> >
> >Thanks
> >
> >
> > 
> >
> >
> >Hillel Miller>
> >
> >
> >-----Original Message-----
> >From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On 
> Behalf Of John
> >Havlicek
> >Sent: Thursday, January 25, 2007 3:42 AM
> >To: sv-ac@eda-stds.org
> >Subject: Re: [sv-ac] reminder to vote on mantis 1550
> >
> >Hillel & Ed:
> >
> >I think there are several things going on here.
> >
> >First, based on 9.3.1, I think that the declaration assignments for
> >static variables execute as part of 
> >
> >   initialize the values of all nets and variables
> >
> >Then the initialization events are scheduled into the time 0 slot.
> >This does not mean that any assignments from an initial block are
> >performed yet.  
> >
> >Then, assuming that there is some event, we execute the time 0 slot.
> >
> >Then the preponed region of the time 0 slot is executed.
> >
> >Thus, the declaration assignments for static variables will influence
> >the preponed values in the time 0 slot.
> >
> >If $sampled refers to a static variable with declaration assignment,
> >then I think that in the time 0 slot the value from the declaration
> >assignment should be used rather than the default initial 
> value for the
> >type of the variable.  
> >
> >The statement in the proposal that $sampled returns the 
> default intial
> >value (presumably of the type) of its argument in the time 0 
> slot could
> >therefore be inconsistent with the statement that $sampled 
> returns the
> >preponed value of its argument in the current time slot, and should
> >probably either be removed or clarified.
> >
> >I think that according to 9.3.1, assignments in an initial 
> block will be
> >scheduled for the active region of the time 0 slot.  These 
> assignments
> >do not, I believe, affect the preponed values in the time 0 
> slot.  If we
> >consider $sampled always to return the preponed value, then initial
> >block assignments will not affect $sampled in the time 0 slot.
> >
> >Hillel, are you asking for the defintion of $sampled to be 
> influenced by
> >initial block assignments in the time 0 slot?  If so, then the
> >definition of $sampled needs to be changed to distinguish the time 0
> >slot from all the other time slots.  I would like to see a strong
> >rationale for such an inconsistency, one that explains, 
> e.g., why static
> >variables with declaration assignments cannot be used.
> >
> >Best regards,
> >
> >John H.
> >
> >  
> >
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> >>Thread-Topic: [sv-ac] reminder to vote on mantis 1550
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> >>Acc/JcA24JDBTV1VQc2QjprTXfKfWwAlgkfgAAIJ6XAAA6aw4AAEm8jwAAAfAlA=
> >>From: "Miller Hillel-R53776" <r53776@freescale.com>
> >>
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> >>
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> >>
> >>Still what is wrong with the proposal to use the value after 
> >>initialization at time 0? Where does this break consistency?
> >>
> >>________________________________
> >>
> >>From: Eduard Cerny [mailto:Eduard.Cerny@synopsys.com]=20
> >>Sent: Wednesday, January 24, 2007 8:27 PM
> >>To: Miller Hillel-R53776; Eduard Cerny; Havlicek John-r8aaau; 
> >>sv-ac@eda-stds.org
> >>Subject: RE: [sv-ac] reminder to vote on mantis 1550
> >>
> >>
> >>Hi Hillel,
> >>=20
> >>apart from the uesr initialization, what is really the problem with 
> >>the current definition? Yes, it can happen when there is a clocking 
> >>event at time 0, or if you have $past with longer number of 
> clocks to 
> >>go back, etc.
> >>=20
> >>Best regards,
> >>ed
> >>=20
> >>PS the forced initialization can be a feature of a tool, 
> not the LRM.
> >>=20
> >>
> >>
> >>________________________________
> >>
> >>	From: Miller Hillel-R53776 [mailto:r53776@freescale.com]=20
> >>	Sent: Wednesday, January 24, 2007 1:14 PM
> >>	To: Eduard Cerny; Havlicek John-r8aaau; sv-ac@eda-stds.org
> >>	Subject: RE: [sv-ac] reminder to vote on mantis 1550
> >>=09
> >>=09
> >>	Ed,
> >>	=20
> >>	What $ functions use $sampled values which are to be before time
> >>    
> >>
> >0?
> >  
> >
> >>	=20
> >>	Does this happen when there is a "clocking event" at time
> >>    
> >>
> >zero?=20
> >  
> >
> >>	=20
> >>	Why can't we take the route of using the values after
> >>    
> >>
> >initialization 
> >  
> >
> >>as the $sampled value in the first preponed region at time 0? What 
> >>does this break?
> >>	=20
> >>	There also needs to be away to allow the user to control the 
> >>initialization of the $functions at time Zero. This could 
> be needed if
> >>    
> >>
> >
> >  
> >
> >>a counter example is produced by a formal tool that needs to be 
> >>replayed in simulation. If the $sampled at the first 
> preponed region 
> >>is from the time 0 initilization stage then this is doable.
> >>	=20
> >>	Thanks
> >>	Hillel
> >>	=20
> >>	=20
> >>	=20
> >>________________________________
> >>
> >>	From: Eduard Cerny [mailto:Eduard.Cerny@synopsys.com]=20
> >>	Sent: Wednesday, January 24, 2007 4:31 PM
> >>	To: Miller Hillel-R53776; Havlicek John-r8aaau;
> >>    
> >>
> >sv-ac@eda-stds.org
> >  
> >
> >>	Subject: RE: [sv-ac] reminder to vote on mantis 1550
> >>=09
> >>=09
> >>	Hello Hillel,
> >>	But the functions use $sampled values which are to be before
> >>    
> >>
> >time 0. 
> >  
> >
> >>Hence the initialization to the default value of the type. 
> What else 
> >>would you suggest?ed
> >>	=20
> >>
> >>
> >>________________________________
> >>
> >>		From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org]
> >>    
> >>
> >On Behalf Of 
> >  
> >
> >>Miller Hillel-R53776
> >>		Sent: Wednesday, January 24, 2007 8:53 AM
> >>		To: Havlicek John-r8aaau; sv-ac@eda-stds.org
> >>		Subject: RE: [sv-ac] reminder to vote on mantis 1550
> >>	=09
> >>	=09
> >>
> >>		Hi,
> >>
> >>		I vote no even though I am not elligible. The reason is
> >>    
> >>
> >that it is 
> >  
> >
> >>not clear what the intialized values are of the $ functions.
> >>
> >>		The current schedular code shows an initialization
> >>    
> >>
> >process, before 
> >  
> >
> >>going into the first preponed area (see below). This means that the 
> >>initial value of an expression is determined by its 
> initilization at 
> >>time slot 0 and not by its default type value as specified in the 
> >>proposal.
> >>
> >>		execute_simulation {
> >>
> >>		T =3D 0;
> >>
> >>		initialize the values of all nets and variables;
> >>
> >>		schedule all initialization events into time 0 slot;
> >>
> >>		while (some time slot is nonempty) {
> >>
> >>		move to the next future nonempty time slot and set T;=20
> >>
> >>		execute_time_slot (T);
> >>
> >>		}
> >>
> >>		}
> >>
> >>		Hillel Miller>
> >>
> >>
> >>    
> >>
> >
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> >
> >  
> >
> 
> 
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