[Rivet] AGILe and PYTUNE

[Peter Skands]

Hi,

MSTP(5) is only intended as a convenience for users that *just* want a specific 
tune. It is 100% equivalent to the construction:

       CALL PYTUNE(ITUNE)
       CALL PYINIT(...)

For users that desire more flexibility (or me, when I make new tunes), it is 
completely possible to take control back and make a construction like:

C...Set base tune
       CALL PYTUNE(ITUNE)
C...Insert user modifications here
       CALL PYGIVE('PARP(64)=2D0')
       ...
C...Force PYINIT to *not* call PYTUNE
       CALL PYGIVE('MSTP(5)=0')
       CALL PYINIT(...)

Would that work for you?

Peter

On 12/3/10 7:21 PM, Andy Buckley wrote:
> On 03/12/10 16:53, Gavin Hesketh wrote:
>> Dear AGILe authors,
>> I've just been playing around with the fortran pythia. I'm sure you know
>> recent versions have the PYTUNE function, which allows you to select any
>> of the "standard" tunes, by setting the MSTP(5) parameter.
>>
>> But, if I want to use this feature while also varying one parameter that
>> is part of that tune, eg by passing the following parameter file when I
>> call agile-runmc:
>>
>> MSTP(5) 105
>> PARP(64) 2
>>
>> then my choice of PARP(64) is overwritten by PYTUNE. iirc, he way to
>> avoid this is to set MSTP(5), call PYINIT, then set the other parameters.
>>
>> I wondered if anyone had figured out how to do such a thing with agile,
>> or if I simply can't use the MSTP(5)/PYTUNE functionality and have to
>> set all the tune variables by hand?
>
> Hi Gavin,
>
> As far as I'm aware, PYTUNE will stomp all over any user-specific
> settings, so slight variations on PYTUNE tunes are not possible. I
> mentioned this to Peter Skands (CC'd) a while ago, so maybe the latest
> version of PYTHIA does now support customising settings on top of
> PYTUNE... Peter?
>
> If not, is it possible to structure AGILe's calls to the PYTHIA routines
> such that PYTUNE will be called first (with a special-case param passing
> of MSTP(5)) and then PYGIVE be called for all the other params?
>
> I'll very happily make an AGILe patch release to incorporate this (as
> well as any new Fortran generator interfaces that people supply...
> MC at NLO, anyone?!)
>
> Andy
>