[petsc-dev] SETERRQ in fortran

[Jed Brown]

"Smith, Barry F." <bsmith at mcs.anl.gov> writes:

>> On Jan 5, 2018, at 5:00 PM, Jed Brown <jed at jedbrown.org> wrote:
>> 
>> "Smith, Barry F." <bsmith at mcs.anl.gov> writes:
>> 
>>>> On Jan 5, 2018, at 4:18 PM, Jed Brown <jed at jedbrown.org> wrote:
>>>> 
>>>> "Smith, Barry F." <bsmith at mcs.anl.gov> writes:
>>>> 
>>>>>> On Jan 5, 2018, at 12:45 PM, Jed Brown <jed at jedbrown.org> wrote:
>>>>>> 
>>>>>> "Smith, Barry F." <bsmith at mcs.anl.gov> writes:
>>>>>> 
>>>>>>>> On Jan 4, 2018, at 5:10 PM, Blaise A Bourdin <bourdin at lsu.edu> wrote:
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>>> On Jan 4, 2018, at 3:16 PM, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> It's changed a bit.  It is better but you need to understand how the new one works, so take a few minutes to see how it works before converting.
>>>>>>>> Got it.
>>>>>>>> An example or a link to the fortran macro definition from the man page would be nice 
>>>>>>>> I am confused about the rationale for putting the endif in the macro, though.
>>>>>>> 
>>>>>>> It matches the C paradigm
>>>>>> 
>>>>>> Hardly.
>>>>> 
>>>>>  It matches the paradigm as close as can be reasonable done.
>>>>> 
>>>>>  I debated putting the then into the macros also.
>>>>> 
>>>>>> #define SETERRQ(c,ierr,s)  then ;call PetscError(c,ierr,0,s);return;endif
>>>>> 
>>>>>  So usage would be 
>>>>> 
>>>>>     if (bad) SETERRQ(); 
>>>>> 
>>>>> would that be better.
>>>> 
>>>> No, Fortran isn't C.
>>>> 
>>>> if (bad) then
>>>>     SETERRQ(...)
>>>> endif
>>>> 
>>>> It doesn't get used so much from Fortran that we need to conceal the
>>>> language constructs.
>>> 
>>>   It will, eventually I want all Fortran examples/tests to have checks on every call (like with have in C).
>> 
>> CHKERRQ does the if internally, so it also has the endif.
>
>   What is the relevance of this statement.

"checks on every call" are relevant to CHKERRQ, not SETERRQ.  CHKERRQ is
self-contained because it includes the entire if-then-endif.

>> SETERRA/SETERRQ is used a total of 34 times in 17 Fortran files.
>> SETERRQ is used a median of zero times and an average of less than 1 in
>> the C examples.
>
>    I am not sure why you are saying this. My resistance to change has nothing to do with how often it is used. 

I thought you were concerned with the clutter of

  if (cond) then SETERRQ(...); endif

instead of

  if (cond) then SETERRQ(...)

>    I am leaning to changing it but don't want to until all the test harness branches etc get into master. So it will be a few days.

Okay to make this change now?

>> 
>>>> 
>>>>> 
>>>>> 
>>>>>> This Fortran:
>>>>>> 
>>>>>> #define SETERRQ(c,ierr,s)  ;call PetscError(c,ierr,0,s);return;endif
>>>>>> 
>>>>>> This would be like writing this C
>>>>>> 
>>>>>> #define SETERRQ(c,ierr,s) return PetscError(...); }
>>>>>> 
>>>>>> to be used like
>>>>>> 
>>>>>> if (BAD) { SETERRQ(comm, ierr, "why")
>>>>>> 
>>>>>> which is just bananas and still not as gross as the Fortran.  You might
>>>>>> not have noticed this because SETERRQ is not called from any of PETSc's
>>>>>> Fortran examples.
>>>>> 
>>>>>   But SETERRA() is and has the same pattern.
>>>> 
>>>> It isn't syntactically correct when !defined(PETSC_USE_ERRORCHECKING).
>>>> The endif isn't going to kill anyone and pulling it out of the macro
>>>> will make it easier to understand and avoid the circus antics when used
>>>> in any context other than a positive conditional with no else clause.
>>> 
>>>   I'll take this under advisement. Of course in our examples the endif will ALWAYS be on the same line as the rest. Using three lines for a SETERRQ() is ugly.
>>> 
>>> 
>>>> 
>>>>>> 
>>>>>>>> Beside not having unmatched if / end if in my code, in a select case construct, I have to write something as ugly as
>>>>>>>> 
>>>>>>>> select case (i)
>>>>>>>> 	case(1) 
>>>>>>>> 		!do something
>>>>>>>> 	case(2)
>>>>>>>> 		!do something else
>>>>>>>> 	case default
>>>>>>>> 		if (0 == 0) then
>>>>>>>> 			SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_ARG_OUTOFRANG,”invalid value”)
>>>>>>>> end select
>>>>>>>> 
>>>>>>> What is ugly about this ? except that you put the SETERRQ on a new line which you did not need to do.
>>>>>> 
>>>>>> Reread the above code.  Requiring the dummy opening if statement is nuts.
>>>>> 
>>>>>  Agreed. He should not use SETERRQ() in this case, should call the error functions directly)
>>>>> 
>>>>>> 
>>>>>>> How do you want to write it so it is prettier?
>>>>>> 
>>>>>> SETERRQ should not include that endif.  CHKERRQ has the opening if and
>>>>>> thus needs the closing too (so it's as intended).  Also note that your
>>>>>> first reply to Blaise was talking about CHKERRQ when he was asking about
>>>>>> SETERRQ.
>>>>> 
>>>>>   Hmm, I'm not sure about. Oh well, it doesn't matter. You have convinced me of anything.