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ACTS
Experiment-independent tracking
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ACTS
Experiment-independent tracking
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Particle identifier that encodes additional event information. More...
#include <ActsFatras/EventData/Barcode.hpp>
Public Types | |
| using | GenerationId = std::uint8_t |
| using | ParticleId = std::uint32_t |
| using | PrimaryVertexId = std::uint16_t |
| using | SecondaryVertexId = std::uint16_t |
| using | SubParticleId = std::uint32_t |
Public Member Functions | |
| constexpr | Barcode ()=default |
| Empty barcode. | |
| constexpr | Barcode (Barcode &&)=default |
| Move constructor. | |
| constexpr | Barcode (const Barcode &)=default |
| Copy constructor. | |
| constexpr std::vector< std::uint32_t > | asVector () const |
| Export barcode as vector. | |
| constexpr GenerationId | generation () const |
| Return the generation identifier. | |
| std::size_t | hash () const |
| Get hash of the barcode. | |
| constexpr bool | isValid () const |
| Barcode | makeDescendant (SubParticleId sub=0u) const |
| Construct a new barcode representing a descendant particle. | |
| Barcode & | operator= (Barcode &&)=default |
| Move assignment operator. | |
| Barcode & | operator= (const Barcode &)=default |
| Copy assignment operator. | |
| bool | operator== (const Barcode &) const =default |
| Compare two barcodes. | |
| constexpr ParticleId | particle () const |
| Return the particle identifier. | |
| constexpr SubParticleId | subParticle () const |
| Return the sub-particle identifier. | |
| constexpr Barcode | vertexId () const |
| Reduce the barcode to the vertex identifier. | |
| constexpr PrimaryVertexId | vertexPrimary () const |
| Return the primary vertex identifier. | |
| constexpr SecondaryVertexId | vertexSecondary () const |
| Return the secondary vertex identifier. | |
| constexpr Barcode | withData (std::span< std::uint32_t > data) |
| Create a new barcode from a vector. | |
| constexpr Barcode | withGeneration (GenerationId id) const |
| Create a new barcode with a different generation identifier. | |
| constexpr Barcode | withoutSubparticle () const |
| Reduce the barcode to the particle identifier. | |
| constexpr Barcode | withParticle (ParticleId id) const |
| Create a new barcode with a different particle identifier. | |
| constexpr Barcode | withSubParticle (SubParticleId id) const |
| Create a new barcode with a different sub-particle identifier. | |
| constexpr Barcode | withVertexPrimary (PrimaryVertexId id) const |
| Create a new barcode with a different primary vertex identifier. | |
| constexpr Barcode | withVertexSecondary (SecondaryVertexId id) const |
| Create a new barcode with a different secondary vertex identifier. | |
Static Public Member Functions | |
| static constexpr Barcode | Invalid () |
| static constexpr bool | isValid (const Barcode &b) |
| Check validity of the barcode. | |
Particle identifier that encodes additional event information.
The barcode has to fulfill two separate requirements: be able to act as unique identifier for particles within an event and to encode details on the event structure for fast lookup. Since we only care about tracking here, we need to support two scenarios:
The vertex information is encoded as two numbers that define the primary and secondary vertex. The primary vertex must be non-zero. Particles with a zero secondary vertex originate directly from the primary vertex.
Within one vertex (primary+secondary) each particle is identified by a particle, generation, and sub-particle number. Particles originating from the vertex must have zero generation and zero sub-particle number; a consequence is that only non-zero generation can have non-zero sub-particle numbers. A non-zero generation indicates that the particle is a descendant of the original particle, e.g. from interactions or decay, while the sub-particle number identifies the descendant particle.
With this encoding, non-primary particles and their primary parent can be easily identified at the expense of not storing the exact decay history.
A barcode with all elements set to zero (the default value) is an invalid value that can be used e.g. to mark missing or unknown particles.
A particle generated in a primary interaction might have the barcode
2|0|14|0|0 -> vertex=2 (primary), particle=14, generation=0, sub=0
A simulation module might generate an interaction and create two new particles. These are descendants of the initial particle and the simulation module can generate the new barcodes directly by increasing the generation number and choosing sub-particle identifiers:
2|0|14|1|0 -> vertex=2 (primary), particle=14, generation=1, sub=0 2|0|14|1|1 -> vertex=2 (primary), particle=14, generation=1, sub=1
If these secondary particles generate further tertiary particles the barcode would be e.g.
2|0|14|2|0 -> vertex=2 (primary), particle=14, generation=2, sub=0
The hierarchical nature of the barcode allows barcode creation without a central service. Since the full history is not stored, generated barcodes for higher-generation particles can overlap when generated by independent interactions. Assuming an initial primary particle with barcode
3|4|5|0|0 -> particle=5
a first interaction might create a secondary particle by increasing the generation number (without destroying the initial particle)
3|4|5|1|0 -> particle=5, generation+=1, first sub-particle
The initial particle gets simulated further and at another step a second interaction also creates a new particle. Since it knows nothing about the previously created particle (no central service), it will generate
3|4|5|1|0 -> particle=5, generation+=1, first sub-particle
which is identical to the previously create barcode. These cases can be easily solved by renumbering the sub-particle identifier within each generation to contain unique values. However, this can only be done when all particles are known.
| using ActsFatras::Barcode::GenerationId = std::uint8_t |
| using ActsFatras::Barcode::ParticleId = std::uint32_t |
| using ActsFatras::Barcode::PrimaryVertexId = std::uint16_t |
| using ActsFatras::Barcode::SecondaryVertexId = std::uint16_t |
| using ActsFatras::Barcode::SubParticleId = std::uint32_t |
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constexprdefault |
Empty barcode.
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constexprdefault |
Copy constructor.
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constexprdefault |
Move constructor.
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constexpr |
Export barcode as vector.
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constexpr |
Return the generation identifier.
| std::size_t ActsFatras::Barcode::hash | ( | ) | const |
Get hash of the barcode.
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staticconstexpr |
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constexpr |
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staticconstexpr |
Check validity of the barcode.
| Barcode ActsFatras::Barcode::makeDescendant | ( | SubParticleId | sub = 0u | ) | const |
Construct a new barcode representing a descendant particle.
| sub | sub-particle index of the new barcode. |
Move assignment operator.
Copy assignment operator.
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default |
Compare two barcodes.
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constexpr |
Return the particle identifier.
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constexpr |
Return the sub-particle identifier.
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constexpr |
Reduce the barcode to the vertex identifier.
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constexpr |
Return the primary vertex identifier.
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constexpr |
Return the secondary vertex identifier.
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nodiscardconstexpr |
Create a new barcode from a vector.
| data | Vector containing exactly 5 elements |
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nodiscardconstexpr |
Create a new barcode with a different generation identifier.
| id | Generation identifier to set |
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constexpr |
Reduce the barcode to the particle identifier.
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nodiscardconstexpr |
Create a new barcode with a different particle identifier.
| id | Particle identifier to set |
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nodiscardconstexpr |
Create a new barcode with a different sub-particle identifier.
| id | Sub-particle identifier to set |
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nodiscardconstexpr |
Create a new barcode with a different primary vertex identifier.
| id | Primary vertex identifier to set |
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nodiscardconstexpr |
Create a new barcode with a different secondary vertex identifier.
| id | Secondary vertex identifier to set |
1.15.0