RE: state notation code flags

["Mark Rivers" <rivers@cars.uchicago.edu>]

Hi Patrick,
 
What is it you are trying to do?  You are doing both pvPuts and looking for external changes to the same PV?
 
If so, then one solution is to ignore events which correspond to the value that your SNL program set with pvPut, and only act on events with values that must have been done by some external agent.  Here is an example from one of my programs:
int     abort;       assign abort        to "{P}{R}Abort.VAL";
monitor abort;
evflag abortMon;        sync abort      abortMon;
...
ss xpsTrajectoryAbort {
    state monitorAbort {
        when ((efTestAndClear(abortMon)) && (abort==1) &&
              (execState==EXECUTE_STATE_EXECUTING)) {
...
            abort=0;
            pvPut(abort);
        } state monitorAbort
    }
}
In this case abort can be set to 1 by the user from outside the SNL program.  If that happens then the SNL program takes some appropriate action, and does a pvPut of abort back to 0.  That would cause another event to be received, but I ignore that event in the when clause()
        when ((efTestAndClear(abortMon)) && (abort==1) &&
              (execState==EXECUTE_STATE_EXECUTING)) {
This will always clear event flags on the abort PV, but will only do the logic inside the when if abort is 1 and execState is EXECUTE_STATE_EXECUTING.
 
Mark
 

________________________________

From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu]
Sent: Sat 10/3/2009 12:37 AM
To: Mark Rivers
Cc: jemian@anl.gov; tech-talk@aps.anl.gov
Subject: Re: state notation code flags



I see, thank you. So is there a way around this, that is to make sure
the monitors are received and the flag is set before the call to efClear
is made, or some way to make a particular pvPut not have channel access
send out monitors for that record?

Mark Rivers wrote:
>> I think I have figured it out, the following code shows it the most
>> clearly. Adding SYNC to the pvPut command does not seem to ensure that
>> it will finish before the next command is processed:
>>    
> 
> The pvPut command did "finish" before the efClear command was executed.  That means that it wrote its value to the record, and processed that record and any records that process as a result of processing that record.   That record told channel access to send out monitors on that PV to all clients, including your SNL program.  It does NOT wait for those monitors to be received; it simply requests channel access to send them, which is then done asynchronously.  So the event flag in your SNL program will be set some time after you do the pvPut.  What you are observing is the expected and documented behavior of EPICS.
> 
> Mark
> 
> 
>
>
> ________________________________
>
> From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu]
> Sent: Fri 10/2/2009 7:03 PM
> To: jemian@anl.gov
> Cc: Mark Rivers; tech-talk@aps.anl.gov
> Subject: Re: state notation code flags
>
>
>
> I think I have figured it out, the following code shows it the most
> clearly. Adding SYNC to the pvPut command does not seem to ensure that
> it will finish before the next command is processed:
>
> program sncTest
>
> float request_maximum_velocity;
> assign request_maximum_velocity to "H3:TEST";
> monitor request_maximum_velocity;
> evflag request_maximum_velocityEvent;
> sync request_maximum_velocity request_maximum_velocityEvent;
>
>
> ss ss1 {
>         state init {
>                 when () {
>                         efClear(request_maximum_velocityEvent);
>
>                         request_maximum_velocity = 40;
>                         pvPut(request_maximum_velocity, SYNC);
>                         efClear(request_maximum_velocityEvent);
>                 } state wait
>         }
>
>         state wait {
>                 when () {
>                         if (efTest(request_maximum_velocityEvent)) {
>                                 printf("flag set\n");
>                         }
>                 } state wait
>         }
> }
>
>
>
> Pete R. Jemian wrote:
>  
>> sounds a bit off ... show the code
>>
>> Patrick Thomas wrote:
>>    
>>> I think I have it narrowed down. It appears that when I set variable1
>>> equal to variable2 and variable2 has a flag synced to it (variable1
>>> does not), and then do a pvPut on variable1, sometimes the flag is
>>> set on variable2 and sometimes it isn't. Am I correct? Why does this
>>> occur?
>>>
>>> Thank you,
>>> Patrick
>>>
>>> Mark Rivers wrote:
>>>      
>>>> Patrick,
>>>>
>>>> Event flags can be explicitly set, which is typically used to allow
>>>> communication between state sets.  Or event flags can be synced to a
>>>> PV,
>>>> and will be set whenever a monitor is received for that PV, as in the
>>>> example I sent you.
>>>>
>>>> You can use the efTest() function outside of a when statement, just
>>>> like
>>>> any other function.
>>>>
>>>> Mark
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Patrick Thomas [mailto:thomas_p@ligo-wa.caltech.edu] Sent:
>>>> Thursday, October 01, 2009 5:20 PM
>>>> To: Mark Rivers
>>>> Cc: tech-talk@aps.anl.gov
>>>> Subject: Re: state notation code flags
>>>>
>>>> Hi Mark,
>>>>
>>>> Are the flags on a monitored variable set whenever the monitored
>>>> variable is used in the code, including a pvPut, pvGet, assignment,
>>>> calculation, or print statement? Is there a way to test if the flag
>>>> is set besides an efTest in a when statement?
>>>>
>>>> Thank you,
>>>> Patrick
>>>>
>>>> Mark Rivers wrote:
>>>>
>>>>        
>>>>> Hio Patrick,
>>>>>
>>>>> Here are some code snippets from one of my SNL programs.  It has a
>>>>>   
>>>>>          
>>>> variable nelements assigned to a PV, and a monitor on that PV.  It has
>>>> an event flag, nelementsMon that is synced to nelements.  Whenever
>>>> nelements changes the event flag will be set.  In the init state I
>>>> clear
>>>> the event flag, just to be sure it is clear when the SNL code starts
>>>> running (after all PVs connect).  I then use efTestAndClear in a when
>>>> statement to take actions when that event flag is set, and to clear it.
>>>> This works fine for me.
>>>>
>>>>        
>>>>> int     nelements;   assign nelements    to "{P}{R}Nelements.VAL";
>>>>> monitor nelements;
>>>>> evflag nelementsMon;    sync nelements  nelementsMon;
>>>>>
>>>>>
>>>>>     /* Initialize things when first starting */
>>>>>     state init {
>>>>>         when() {
>>>>>             /* Clear all event flags */
>>>>> ...
>>>>>
>>>>>             efClear(nelementsMon);
>>>>>         } state monitor_inputs
>>>>>     }
>>>>>
>>>>>
>>>>> ...
>>>>>
>>>>>     state monitor_inputs {
>>>>>
>>>>> ...
>>>>>
>>>>>         when(efTestAndClear(nelementsMon) && (nelements>=1)) {
>>>>>             /* If nelements changes, then change endPulses to this
>>>>>   
>>>>>          
>>>> value,
>>>>
>>>>        
>>>>>              * since this is what the user normally wants.  endPulses
>>>>>   
>>>>>          
>>>> can be
>>>>
>>>>        
>>>>>              * changed again after changing nelements if this is
>>>>>   
>>>>>          
>>>> desired. */
>>>>
>>>>        
>>>>>             if (moveMode == MOVE_MODE_RELATIVE)
>>>>>                 endPulses = nelements;
>>>>>             else
>>>>>                 endPulses = nelements-1;
>>>>>             pvPut(endPulses);
>>>>>         } state monitor_inputs
>>>>>     }
>>>>>
>>>>> Mark
>>>>>
>>>>> ________________________________
>>>>>
>>>>> From: tech-talk-bounces@aps.anl.gov on behalf of Patrick Thomas
>>>>> Sent: Wed 9/30/2009 10:35 PM
>>>>> To: tech-talk@aps.anl.gov
>>>>> Subject: state notation code flags
>>>>>
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> I was wondering if there is a way to track at what point in the state
>>>>> notation code evflags are getting set and cleared, or if someone could
>>>>> clarify under what conditions they get set. I'm having trouble with
>>>>>   
>>>>>          
>>>> them
>>>>
>>>>        
>>>>> getting set somewhere and not being cleared, but I'm not sure where.
>>>>>
>>>>> Thank you,
>>>>> Patrick
>>>>>
>>>>>
>>>>>     
>>>>>          
>>>> 
>>>>        
>
>
>
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