Condition "If" statement evaluation in a parameter

Hi Peter,

The expression that you need to enter should be a python expression.
Not a fortran one.
The expression should also be a one line expression. So they are no
way to introduce a "IF" statement.

In principle you can use the python trick (via the fct_library):
myif = lambda cond, T, F: cond and T or F
indeed:
myif(1, 2, 3) -> 3
myif(0, 2, 3) -> 2
BUT they are a side effect:
myif(0, 0, 3) -> 3 (and not 0)

But I'm pretty sure that MG5 will not support it. (Convert such
expression in C/Fortran will not be easy)
Let me talk with the Full MG Team/UFO Team about this point. And then
I'll go back to you.

Cheers,

Olivier

On 01-avr.-11, at 12:27, Manning wrote:

> New question #151288 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/151288
>
> Hi MG team,
>
> I have some parameters which contain conditional statements
> dependent on the values of other internal and external parameters.
> The model is in UFO format from FeynRules. For example, the width of
> my U11p particle is:
>
> WU11p = Parameter(name = 'WU11p',
> nature = 'internal',
> type = 'real',
> value = '2*((aEW*D11p*(1 + D11p**2/
> (2.*MWmu11**2))*(1 - MWmu11**2/D11p**2)**2)/(16.*sw**s2) + (aEW*(1 -
> MWmu11**2/U11p**2)**2*U11p*(1 + U11p**2/(2.*MWmu11**2)))/
> (16.*sw**s2) + If(ymb.ne.0,(aEW*Sqrt((B11p**2 - (MWmu11**2 +
> ymb**2)**2)*(B11p**2 - (MWmu11**2 - ymb**2)**2))*((B11p**2 + ymb**2)/
> (2.*B11p**2) + (B11p**2 - ymb**2)**2/(2.*B11p**2*ymb**2) - MWmu11**2/
> B11p**2))/(8.*sw**2*B11p),(aEW*B11p*(1 - MWmu11**2/B11p**2)**2*(1 +
> B11p**2/(2.*MWmu11**2)))/(16.*sw**s2)) + If(ymc.ne.0,
> (aEW*Sqrt((C11p**2 - (MWmu11**2 + ymc**2)**2)*(C11p**2 - (MWmu11**2
> - ymc**2)**2))*((C11p**2 + ymc**2)/(2.*C11p**2) + (C11p**2 -
> ymc**2)**2/(2.*C11p**2*ymc**2) - MWmu11**2/C11p**2))/(8.*sw**2*C11p),
> (aEW*C11p*(1 - MWmu11**2/C11p**2)**2*(1 + C11p**2/(2.*MWmu11**2)))/
> (16.*sw**s2)) + If(yms.ne.0,(aEW*Sqrt((S11p**2 - (MWmu11**2 +
> yms**2)**2)*(S11p**2 - (MWmu11**2 - yms**2)**2))*((S11p**2 + yms**2)/
> (2.*S11p**2) + (S11p**2 - yms**2)**2/(2.*S11p**2*yms**2) - MWmu11**2/
> S11p**2))/(8.*sw**2*S11p),(aEW*S11p*(1 - MWmu11**2/S11p**2)**2*(1 +
> S11p**2/(2.*MWmu11**2)))/(16.*sw**s2)) + If(ymt.ne.0,
> (aEW*Sqrt((T11p**2 - (MWmu11**2 + ymt**2)**2)*(T11p**2 - (MWmu11**2
> - ymt**2)**2))*((T11p**2 + ymt**2)/(2.*T11p**2) + (T11p**2 -
> ymt**2)**2/(2.*T11p**2*ymt**2) - MWmu11**2/T11p**2))/(8.*sw**2*T11p),
> (aEW*T11p*(1 - MWmu11**2/T11p**2)**2*(1 + T11p**2/(2.*MWmu11**2)))/
> (16.*sw**s2)))',
> texname = '\\text{WU11p}')
>
> When I try to run MG5, it gives me the error:
>
> Export UFO model to MG4 format
> ERROR: Illegal character '.'
> ERROR: Syntax error at 'ne'
> Command "output test5" interrupted with error:
> NameError : global name 'MadGraph5Error' is not defined
> Please report this bug on https://bugs.launchpad.net/madgraph5
> More information is found in 'MG5_debug'.
> Please attach this file to your report.
>
> Is it possible to do what I am trying to do? For this case I could
> find a workaround, but there is a case which depends on the
> evaluated value of the particle masses, which I do not know a
> priori. Thanks for your help.
>
> Cheers,
>
> Peter M.
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Thanks Olivier. I think I'm at the point where I realize it is making life
more complicated to NOT write an external program to calculate widths and
print out the param_card values for specific model parameters. But, being
able to have a parameter which contains a conditional statement would still
be useful.

Thanks,

Peter

On Fri, Apr 1, 2011 at 12:48 PM, Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #151288 on MadGraph5 changed:
> https://answers.launchpad.net/madgraph5/+question/151288
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi Peter,
>
> The expression that you need to enter should be a python expression.
> Not a fortran one.
> The expression should also be a one line expression. So they are no
> way to introduce a "IF" statement.
>
> In principle you can use the python trick (via the fct_library):
> myif = lambda cond, T, F: cond and T or F
> indeed:
> myif(1, 2, 3) -> 3
> myif(0, 2, 3) -> 2
> BUT they are a side effect:
> myif(0, 0, 3) -> 3 (and not 0)
>
> But I'm pretty sure that MG5 will not support it. (Convert such
> expression in C/Fortran will not be easy)
> Let me talk with the Full MG Team/UFO Team about this point. And then
> I'll go back to you.
>
> Cheers,
>
> Olivier
>
>
>
>
>
> On 01-avr.-11, at 12:27, Manning wrote:
>
> > New question #151288 on MadGraph5:
> > https://answers.launchpad.net/madgraph5/+question/151288
> >
> > Hi MG team,
> >
> > I have some parameters which contain conditional statements
> > dependent on the values of other internal and external parameters.
> > The model is in UFO format from FeynRules. For example, the width of
> > my U11p particle is:
> >
> > WU11p = Parameter(name = 'WU11p',
> > nature = 'internal',
> > type = 'real',
> > value = '2*((aEW*D11p*(1 + D11p**2/
> > (2.*MWmu11**2))*(1 - MWmu11**2/D11p**2)**2)/(16.*sw**s2) + (aEW*(1 -
> > MWmu11**2/U11p**2)**2*U11p*(1 + U11p**2/(2.*MWmu11**2)))/
> > (16.*sw**s2) + If(ymb.ne.0,(aEW*Sqrt((B11p**2 - (MWmu11**2 +
> > ymb**2)**2)*(B11p**2 - (MWmu11**2 - ymb**2)**2))*((B11p**2 + ymb**2)/
> > (2.*B11p**2) + (B11p**2 - ymb**2)**2/(2.*B11p**2*ymb**2) - MWmu11**2/
> > B11p**2))/(8.*sw**2*B11p),(aEW*B11p*(1 - MWmu11**2/B11p**2)**2*(1 +
> > B11p**2/(2.*MWmu11**2)))/(16.*sw**s2)) + If(ymc.ne.0,
> > (aEW*Sqrt((C11p**2 - (MWmu11**2 + ymc**2)**2)*(C11p**2 - (MWmu11**2
> > - ymc**2)**2))*((C11p**2 + ymc**2)/(2.*C11p**2) + (C11p**2 -
> > ymc**2)**2/(2.*C11p**2*ymc**2) - MWmu11**2/C11p**2))/(8.*sw**2*C11p),
> > (aEW*C11p*(1 - MWmu11**2/C11p**2)**2*(1 + C11p**2/(2.*MWmu11**2)))/
> > (16.*sw**s2)) + If(yms.ne.0,(aEW*Sqrt((S11p**2 - (MWmu11**2 +
> > yms**2)**2)*(S11p**2 - (MWmu11**2 - yms**2)**2))*((S11p**2 + yms**2)/
> > (2.*S11p**2) + (S11p**2 - yms**2)**2/(2.*S11p**2*yms**2) - MWmu11**2/
> > S11p**2))/(8.*sw**2*S11p),(aEW*S11p*(1 - MWmu11**2/S11p**2)**2*(1 +
> > S11p**2/(2.*MWmu11**2)))/(16.*sw**s2)) + If(ymt.ne.0,
> > (aEW*Sqrt((T11p**2 - (MWmu11**2 + ymt**2)**2)*(T11p**2 - (MWmu11**2
> > - ymt**2)**2))*((T11p**2 + ymt**2)/(2.*T11p**2) + (T11p**2 -
> > ymt**2)**2/(2.*T11p**2*ymt**2) - MWmu11**2/T11p**2))/(8.*sw**2*T11p),
> > (aEW*T11p*(1 - MWmu11**2/T11p**2)**2*(1 + T11p**2/(2.*MWmu11**2)))/
> > (16.*sw**s2)))',
> > texname = '\\text{WU11p}')
> >
> > When I try to run MG5, it gives me the error:
> >
> > Export UFO model to MG4 format
> > ERROR: Illegal character '.'
> > ERROR: Syntax error at 'ne'
> > Command "output test5" interrupted with error:
> > NameError : global name 'MadGraph5Error' is not defined
> > Please report this bug on https://bugs.launchpad.net/madgraph5
> > More information is found in 'MG5_debug'.
> > Please attach this file to your report.
> >
> > Is it possible to do what I am trying to do? For this case I could
> > find a workaround, but there is a case which depends on the
> > evaluated value of the particle masses, which I do not know a
> > priori. Thanks for your help.
> >
> > Cheers,
> >
> > Peter M.
> >
> > --
> > You received this question notification because you are a member of
> > MadTeam, which is an answer contact for MadGraph5.
>
> --
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> know that it is solved:
>
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>
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>

We will keep the idea of the if.
And will try to implement it in a future version.