smash::ProcessBranch Class Reference

#include <processbranch.h>

ProcessBranch represents one possible final state of an interaction process.

Each final state has two components;

1. The list of particle types present in this state.
2. The weight of this state, i.e. how probable this outcome is compared to other possible outcomes. Depending on context, this can be either a cross section or a branching ratio.
3. The process id that identifies a certain class of processes. If the outgoing particles are not known yet, e.g. for strings there will be only the weight and the process id.

For example, create a list of decay modes for \(\Delta^+\) resonance:

std::vector<ProcessBranch> deltaplus_decay_modes;
ProcessBranch branch;
branch.set_weight(2);
deltaplus_decay_modes.push_back(branch);
// set_weight erases the previous weight
branch.set_weight(1);
deltaplus_decay_modes.push_back(branch);

Definition at line 134 of file processbranch.h.

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Public Member Functions
	ProcessBranch ()
	Create a ProcessBranch without final states and weight. More...
	ProcessBranch (double w)
	Create a ProcessBranch with with weight but without final states. More...
	ProcessBranch (const ProcessBranch &)=delete
	Copying is disabled. Use std::move or create a new object. More...
virtual	~ProcessBranch ()=default
	Virtual Destructor. More...
void	set_weight (double process_weight)
	Set the weight of the branch. More...
virtual ProcessType	get_type () const =0
virtual const ParticleTypePtrList &	particle_types () const =0
ParticleList	particle_list () const
double	weight () const
double	threshold () const
virtual unsigned int	particle_number () const =0

Protected Attributes
double	branch_weight_
	Weight of the branch, typically a cross section or a branching ratio. More...
double	threshold_ = -1.
	Threshold of the branch. More...

Related Functions
(Note that these are not member functions.)
template<typename Branch >
double	total_weight (const ProcessBranchList< Branch > &l)

Constructor & Destructor Documentation

ProcessBranch() [1/3]

smash::ProcessBranch::ProcessBranch ( )

inline

Create a ProcessBranch without final states and weight.

Definition at line 137 of file processbranch.h.

: branch_weight_(0.) {}

ProcessBranch() [2/3]

smash::ProcessBranch::ProcessBranch ( double  w )

inlineexplicit

Create a ProcessBranch with with weight but without final states.

Parameters

[in]

w

Weight of new branch.

Definition at line 143 of file processbranch.h.

: branch_weight_(w) {}

ProcessBranch() [3/3]

smash::ProcessBranch::ProcessBranch ( const ProcessBranch &  )

delete

Copying is disabled. Use std::move or create a new object.

~ProcessBranch()

virtual smash::ProcessBranch::~ProcessBranch ( )

virtualdefault

Virtual Destructor.

The declaration of the destructor is necessary to make it virtual.

Member Function Documentation

set_weight()

void smash::ProcessBranch::set_weight ( double  process_weight )

inline

Set the weight of the branch.

In other words, how probable this branch is compared to other branches.

Parameters

[in]

process_weight

Weight of the process.

Definition at line 193 of file processbranch.h.

                                                           {
  branch_weight_ = process_weight;
}

get_type()

virtual ProcessType smash::ProcessBranch::get_type ( ) const

pure virtual

Returns

the process type

Implemented in smash::DecayBranch, and smash::CollisionBranch.

particle_types()

virtual const ParticleTypePtrList& smash::ProcessBranch::particle_types ( ) const

pure virtual

Returns

the particle types associated with this branch.

Implemented in smash::DecayBranch, and smash::CollisionBranch.

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particle_list()

ParticleList smash::ProcessBranch::particle_list

(

)

const

Returns

a list of ParticleData initialized with the stored ParticleType objects.

Definition at line 26 of file processbranch.cc.

                                                {
  ParticleList l;
  l.reserve(particle_number());
  for (const auto& type : particle_types()) {
    l.push_back(ParticleData{*type});
  }
  return l;
}

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weight()

double smash::ProcessBranch::weight ( ) const

inline

Returns

the branch weight.

the branch weight

Definition at line 198 of file processbranch.h.

{ return branch_weight_; }

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threshold()

double smash::ProcessBranch::threshold

(

)

const

Returns

the threshold for this branch, i.e. the minimum energy that is required to produce all final-state particles.

Definition at line 35 of file processbranch.cc.

                                      {
  if (threshold_ < 0.) {
    /* Sum up the (minimum) masses of all final-state particles
     * this requires double-precision to ensure that the sum is never
     * smaller than the real sum would be without rounding. */
    double thr = 0.;
    for (const auto& type : particle_types()) {
      thr += type->min_mass_kinematic();
    }
    /* This may round up or down. Up is good. If down
     * we must add one ULP via 'nextafter'. */
    const double rounded = thr;
    threshold_ =
        rounded < thr
            ? std::nextafter(rounded, std::numeric_limits<double>::max())
            : rounded;
  }
  return threshold_;
}

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particle_number()

virtual unsigned int smash::ProcessBranch::particle_number ( ) const

pure virtual

Returns

the number of particles in the final state.

Implemented in smash::DecayBranch, and smash::CollisionBranch.

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Friends And Related Function Documentation

total_weight()

template<typename Branch >

double total_weight ( const ProcessBranchList< Branch > &  l )

related

Parameters

[in]

l

The list of all the processes that would be summed.

Returns

the total weight calculated by summing all weights of the ProcessBranch objects in the list l.

Definition at line 207 of file processbranch.h.

                                                               {
  double sum = 0.;
  for (const auto &p : l) {
    sum += p->weight();
  }
  return sum;
}

Member Data Documentation

branch_weight_

double smash::ProcessBranch::branch_weight_

protected

Weight of the branch, typically a cross section or a branching ratio.

Definition at line 188 of file processbranch.h.

threshold_

double smash::ProcessBranch::threshold_ = -1.

mutableprotected

Threshold of the branch.

Definition at line 190 of file processbranch.h.

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The documentation for this class was generated from the following files:

• src/include/smash/processbranch.h
• src/processbranch.cc