# Class: Reducer _A streaming reduction, authored as symbolic recurrences over its own state rather than as backend code. Folded into the integrator carry so a windowed observable (a sliding-window FC, a running mean) is computed without ever materialising the trajectory. `add` folds an arriving sample in, `evict` takes a leaving one back out, `resync` rebuilds the state exactly from the window when incremental drift would accumulate, and `emit` reads the reduced value out. TVBO lowers all four through the sympy printers, so no backend ships a reducer and adding one is a YAML file rather than code._
URI: [tvbo:Reducer](https://w3id.org/tvbo/Reducer) ```{mermaid} classDiagram class Reducer click Reducer href "./Reducer.html" Reducer : add Reducer --> "*" Assignment : add click Assignment href "./Assignment.html" Reducer : backends Reducer --> "*" String : backends click String href "../http://www.w3.org/2001/XMLSchema#string.html" Reducer : description Reducer --> "0..1" String : description click String href "../http://www.w3.org/2001/XMLSchema#string.html" Reducer : emit Reducer --> "1" String : emit click String href "../http://www.w3.org/2001/XMLSchema#string.html" Reducer : emit_kind Reducer --> "0..1" ReducerEmitKind : emit_kind click ReducerEmitKind href "../../enums/ReducerEmitKind.html" Reducer : evict Reducer --> "*" Assignment : evict click Assignment href "./Assignment.html" Reducer : name Reducer --> "1" String : name click String href "../http://www.w3.org/2001/XMLSchema#string.html" Reducer : replaces Reducer --> "*" String : replaces click String href "../http://www.w3.org/2001/XMLSchema#string.html" Reducer : resync Reducer --> "*" Assignment : resync click Assignment href "./Assignment.html" Reducer : resync_masked Reducer --> "*" Assignment : resync_masked click Assignment href "./Assignment.html" Reducer : state Reducer --> "1..*" String : state click String href "../http://www.w3.org/2001/XMLSchema#string.html" ``` ## Class Properties | Property | Value | | --- | --- | | Class URI | [tvbo:Reducer](https://w3id.org/tvbo/Reducer) | ## Slots | Name | Cardinality and Range | Description | Inheritance | | --- | --- | --- | --- | | [name](../slots/name.qmd) | 1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | Globally unique identifier for the entity | direct | | [description](../slots/description.qmd) | 0..1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | | direct | | [replaces](../slots/replaces.qmd) | *
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | Dotted references to the post-scan pipeline reducers this streams | direct | | [backends](../slots/backends.qmd) | *
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | Codegen backends this recipe is registered for; others recompute | direct | | [emit_kind](../slots/emit_kind.qmd) | 0..1
[ReducerEmitKind](../enums/ReducerEmitKind.qmd) | Whether the reduced value is read out every step or every stride | direct | | [state](../slots/state.qmd) | 1..*
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | The names carried across steps — the reducer's own carry | direct | | [add](../slots/add.qmd) | *
[Assignment](../classes/Assignment.qmd) | Recurrence folding one arriving sample `v` into the state | direct | | [evict](../slots/evict.qmd) | *
[Assignment](../classes/Assignment.qmd) | Recurrence taking one leaving sample `v` back out of the state | direct | | [resync](../slots/resync.qmd) | *
[Assignment](../classes/Assignment.qmd) | Recurrence rebuilding the state exactly from the whole window `x` | direct | | [resync_masked](../slots/resync_masked.qmd) | *
[Assignment](../classes/Assignment.qmd) | Recurrence rebuilding the state from a fixed-size ring in which only `L` rows... | direct | | [emit](../slots/emit.qmd) | 1
[xsd:string](http://www.w3.org/2001/XMLSchema#string) | Expression reading the reduced value out of the state | direct | ## Identifier and Mapping Information ### Schema Source * from schema: https://w3id.org/tvbo ## Mappings | Mapping Type | Mapped Value | | --- | --- | | self | tvbo:Reducer | | native | tvbo:Reducer | ## LinkML Source ### Direct
```yaml name: Reducer description: A streaming reduction, authored as symbolic recurrences over its own state rather than as backend code. Folded into the integrator carry so a windowed observable (a sliding-window FC, a running mean) is computed without ever materialising the trajectory. `add` folds an arriving sample in, `evict` takes a leaving one back out, `resync` rebuilds the state exactly from the window when incremental drift would accumulate, and `emit` reads the reduced value out. TVBO lowers all four through the sympy printers, so no backend ships a reducer and adding one is a YAML file rather than code. from_schema: https://w3id.org/tvbo slots: - name - description attributes: replaces: name: replaces description: Dotted references to the post-scan pipeline reducers this streams. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: string multivalued: true backends: name: backends description: Codegen backends this recipe is registered for; others recompute. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: string multivalued: true emit_kind: name: emit_kind description: Whether the reduced value is read out every step or every stride. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: string(window) domain_of: - Reducer range: ReducerEmitKind state: name: state description: The names carried across steps — the reducer's own carry. from_schema: https://w3id.org/tvbo domain_of: - Node - Reducer range: string required: true multivalued: true add: name: add description: Recurrence folding one arriving sample `v` into the state. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: Assignment multivalued: true inlined_as_list: true evict: name: evict description: Recurrence taking one leaving sample `v` back out of the state. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: Assignment multivalued: true inlined_as_list: true resync: name: resync description: Recurrence rebuilding the state exactly from the whole window `x`. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: Assignment multivalued: true inlined_as_list: true resync_masked: name: resync_masked description: Recurrence rebuilding the state from a fixed-size ring in which only `L` rows are live, selected by mask `m`. Separate from `resync` because a ring sized for the longest window carries rows that are not yet part of it, and summing over them would fold padding into the result. Absent where a reducer has no ring to mask. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: Assignment multivalued: true inlined_as_list: true emit: name: emit description: Expression reading the reduced value out of the state. from_schema: https://w3id.org/tvbo rank: 1000 domain_of: - Reducer range: string required: true class_uri: tvbo:Reducer ```
### Induced
```yaml name: Reducer description: A streaming reduction, authored as symbolic recurrences over its own state rather than as backend code. Folded into the integrator carry so a windowed observable (a sliding-window FC, a running mean) is computed without ever materialising the trajectory. `add` folds an arriving sample in, `evict` takes a leaving one back out, `resync` rebuilds the state exactly from the window when incremental drift would accumulate, and `emit` reads the reduced value out. TVBO lowers all four through the sympy printers, so no backend ships a reducer and adding one is a YAML file rather than code. from_schema: https://w3id.org/tvbo attributes: replaces: name: replaces description: Dotted references to the post-scan pipeline reducers this streams. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: string multivalued: true backends: name: backends description: Codegen backends this recipe is registered for; others recompute. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: string multivalued: true emit_kind: name: emit_kind description: Whether the reduced value is read out every step or every stride. from_schema: https://w3id.org/tvbo rank: 1000 ifabsent: string(window) owner: Reducer domain_of: - Reducer range: ReducerEmitKind state: name: state description: The names carried across steps — the reducer's own carry. from_schema: https://w3id.org/tvbo owner: Reducer domain_of: - Node - Reducer range: string required: true multivalued: true add: name: add description: Recurrence folding one arriving sample `v` into the state. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: Assignment multivalued: true inlined: true inlined_as_list: true evict: name: evict description: Recurrence taking one leaving sample `v` back out of the state. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: Assignment multivalued: true inlined: true inlined_as_list: true resync: name: resync description: Recurrence rebuilding the state exactly from the whole window `x`. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: Assignment multivalued: true inlined: true inlined_as_list: true resync_masked: name: resync_masked description: Recurrence rebuilding the state from a fixed-size ring in which only `L` rows are live, selected by mask `m`. Separate from `resync` because a ring sized for the longest window carries rows that are not yet part of it, and summing over them would fold padding into the result. Absent where a reducer has no ring to mask. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: Assignment multivalued: true inlined: true inlined_as_list: true emit: name: emit description: Expression reading the reduced value out of the state. from_schema: https://w3id.org/tvbo rank: 1000 owner: Reducer domain_of: - Reducer range: string required: true name: name: name description: Globally unique identifier for the entity. from_schema: https://w3id.org/tvbo/common slot_uri: schema:name identifier: true owner: Reducer domain_of: - BrainAtlas - CommonCoordinateSpace - ParcellationEntity - StudyLayout - StudyTemplate - StudyDirectory - StudyFile - DBSProtocol - ClinicalScale - ClinicalScore - SoftwarePackage - SoftwareRequirement - SoftwareEnvironment - Figure - Event - Tractogram - ResultEntity - Activity - CachedArray - MeasureSpec - NamedArray - GraphGenerator - Binding - ProcedureStep - File - StateValue - Observation - Dynamics - StateVariable - Distribution - Parameter - CouplingInput - Argument - Function - FunctionCall - Callable - DerivedParameter - DerivedVariable - DataSource - OptimizationStage - Exploration - Inference - Prior - Likelihood - UpdateRule - Algorithm - Option - BranchSwitch - Continuation - Coupling - EnvironmentVariable - SchedulerDirective - Reducer range: string required: true description: name: description from_schema: https://w3id.org/tvbo rank: 1000 slot_uri: dcterms:description owner: Reducer domain_of: - CommonCoordinateSpace - Dataset - StudyLayout - StudyTemplate - StudyDirectory - StudyFile - ClinicalScore - SoftwarePackage - SoftwareRequirement - SoftwareEnvironment - Figure - Panel - Equation - Stimulus - Event - Tractogram - Matrix - ResultEntity - Activity - Phenotype - MeasureSpec - NamedArray - Network - GraphGenerator - ProcedureStep - File - Node - Edge - Observation - Dynamics - StateVariable - Parameter - CouplingInput - Argument - Function - FunctionCall - Callable - DerivedParameter - DerivedVariable - RandomStream - DataSource - OptimizationStage - Exploration - ExplorationAxis - FreeParameter - Inference - Prior - Likelihood - UpdateRule - AlgorithmStage - TuningObjective - Algorithm - BranchSwitch - Continuation - Integrator - Coupling - RegionMapping - SimulationExperiment - Study - ResultBinding - TimeSeries - NDArray - SpatialDomain - Mesh - SpatialField - FieldStateVariable - BoundaryCondition - PDESolver - PDE - Reducer range: string class_uri: tvbo:Reducer ```