VectorPostprocessors System

The VectorPostprocessors (VPP) System is designed to compute multiple related values each time it is executed. It can be thought of as a Postprocessor that outputs multiple values. For example, if you'd like to sample a solution field across a line, a VPP is a good choice (See PointValueSampler). In addition to outputting the values along the line a VPP can actually output multiple vectors simultaneously. Each vector is given a name, which is the column name. Together, all of the vectors a VPP outputs are output in one CSV file (usually per-timestep).

commentnote

The Reporter System is a newer, more flexible system for computing aggregate values. It is recommended that new objects for aggregate calculations use the Reporter system.

Design

The VPP system builds off from MOOSE's UserObject system. Each VPP contains the full interface of a UserObject but is also expected to declare one or more vectors that will be populated and output by each VPP. There are no restrictions on the lengths of these vectors and the state of these vectors is managed by MOOSE and is automatically "restartable".

Vectors are declared with the declareVector method:

  VectorPostprocessorValue & declareVector(const std::string & vector_name);
(moose/framework/include/vectorpostprocessors/VectorPostprocessor.h)

This method returns a writable reference to a VectorPostprocessorValue that must be captured and stored in the object.

typedef Real ScatterVectorPostprocessorValue;
(moose/framework/include/utils/MooseTypes.h)
commentnote

Developers are responsible for sizing these vectors as needed.

Output

VPP data can vary depending on the type of data being output. Again, the "sample over line" example mentioned in the introduction, a complete set of values will be generated each time the VPP is executed. The VPP system handles this scenario by creating separate output files for each invocation. The form of the output is as follows:


<filebase>_<vector name>_<serial number>.csv

# filebase - the normal output file base
# vector name - the name of the vector postprocessor (normally the input block name for that VPP)
# serial number - a fixed-width (normally four digit) number starting from 0000 and counting up.

In some cases however, a VPP may be accumulating information in time. For example, a user may wish to track values at several locations over time. The output might consist of the coordinates of those positions and the sampled value. In such a scenario, the default separate file output may be cumbersome as each file would effectively have a single line so a script to aggregate the information from all of the separate output files may need to be used. Instead, MOOSE supports an option, which may be of use in these cases:


contains_complete_history = true

By setting this value, you are telling MOOSE that the values in all of the vectors of the given VPP are cumulative. MOOSE will take advantage of this information in multiple ways. First, it will turn off writing the output to separate files and will drop the serial number from the output filename format altogether. Secondly, it will ignore any changed values in the vectors only outputting the newest rows in each vector postprocessor.

Parallel Assumptions

VectorPostprocessors are required to create their complete vectors on processor zero (rank 0). They should use the _communicator to reduce their values to processor zero. Objects that use VPPs must specify how they need the data by calling the getVectorPostprocessorValue() or getScatterVectorPostprocessorValue() functions with the correct arguments.

If the object needing VPP values only needs those values on processor zero it should call:


getVectorPostprocessorValue('the_vpp_parameter_name', 'the_vector_name', false)

The false in that call tells MOOSE that this object does NOT need the vector to be "broadcast" (i.e. "replicated).

If this object does indeed need the VPP data to be broadcast (replicated on all processors) it should make this call:


getVectorPostprocessorValue('the_vpp_parameter_name', 'the_vector_name', true)

In the very special case that a VPP is producing vectors that are num_procs length an object can ask for the value of a VPP to be "scattered" - which means that each processor will receive only the value that corresponds to it's rank (i.e. _values[rank]). This is accomplished by calling:


getScatterVectorPostprocessorValue('the_vpp_parameter_name', 'the_vector_name')

getScatterVectorPostprocessorValue() returns a const ScatterVectorPostprocessorValue &... which is a single scalar value that you don't index into. Each process receives the "correct" value and can just directly use it.

If the data in a VPP is naturally replicated on all processors a VectorPostprocessor should set _auto_broadcast = false in its validParams() like so:


params.set<bool>("_auto_broadcast") = "false";

This tells MOOSE that the data is already replicated and there is no need to broadcast it if another object is asking for it to be broadcast.

TimeData

The time_data parameter produces an additional CSV file containing just the real time and the corresponding time step for any VectorPostprocessor output information. This file may be useful in producing animations or your simulation results.

VectorPostprocessor List

Available Objects

  • Moose App
  • CSVReaderConverts columns of a CSV file into vectors of a VectorPostprocessor.
  • CSVReaderVectorPostprocessorConverts columns of a CSV file into vectors of a VectorPostprocessor.
  • ConstantVectorPostprocessorPopulate constant VectorPostprocessorValue directly from input file.
  • CylindricalAverageCompute a cylindrical average of a variableas a function of radius throughout the simulation domain.
  • EigenvaluesReturns the Eigen values from the nonlinear Eigen system.
  • ElementMaterialSamplerRecords all Real-valued material properties of a material object on quadrature points on elements at the indicated execution points.
  • ElementValueSamplerSamples values of variables on elements.
  • ElementVariablesDifferenceMaxComputes the largest difference between two variable fields.
  • ElementsAlongLineOutputs the IDs of every element intersected by a user-defined line
  • ElementsAlongPlaneOutputs the IDs of every element intersected by a user-defined plane
  • ExtraIDIntegralVectorPostprocessorIntegrates or averages variables based on extra element IDs
  • HistogramVectorPostprocessorCompute a histogram for each column of a VectorPostprocessor
  • IntersectionPointsAlongLineGet the intersection points for all of the elements that are intersected by a line.
  • LeastSquaresFitPerforms a polynomial least squares fit on the data contained in another VectorPostprocessor
  • LeastSquaresFitHistoryPerforms a polynomial least squares fit on the data contained in another VectorPostprocessor and stores the full time history of the coefficients
  • LineFunctionSamplerSample one or more functions along a line.
  • LineMaterialRealSamplerSamples real-valued material properties for all quadrature points in all elements that are intersected by a specified line
  • LineValueSamplerSamples variable(s) along a specified line
  • MaterialVectorPostprocessorRecords all Real-valued material properties of a material object on quadrature points on elements at the indicated execution points.
  • MeshDivisionFunctorReductionVectorPostprocessorPerform reductions on functors based on a per-mesh-division basis
  • NearestPointIntegralVariablePostprocessorCompute element variable integrals for nearest-point based subdomains
  • NodalValueSamplerSamples values of nodal variable(s).
  • PointValueSamplerSample a variable at specific points.
  • PositionsFunctorValueSamplerSample one or more functors at points specified by a Positions object.
  • SideValueSamplerSample variable(s) along a sideset, internal or external.
  • SidesetInfoVectorPostprocessorThis VectorPostprocessor collects meta data for provided sidesets.
  • SpatialUserObjectVectorPostprocessorOutputs the values of a spatial user object in the order of the specified spatial points
  • SphericalAverageCompute a spherical average of a variable as a function of radius throughout the simulation domain.
  • VariableValueVolumeHistogramCompute a histogram of volume fractions binned according to variable values.
  • VectorMemoryUsageGet memory stats for all ranks in the simulation
  • VectorOfPostprocessorsOutputs the values of an arbitrary user-specified set of postprocessors as a vector in the order specified by the user
  • VolumeHistogramCompute a histogram of volume fractions binned according to variable values.
  • WorkBalanceComputes several metrics for workload balance per processor
  • Ray Tracing App
  • PerProcessorRayTracingResultsVectorPostprocessorAccumulates ray tracing results (information about the trace) on a per-processor basis.
  • Solid Mechanics App
  • ADInteractionIntegralComputes the interaction integral, which is used to compute various fracture mechanics parameters at a crack tip, including KI, KII, KIII, and the T stress.
  • AverageSectionValueSamplerCompute the section's variable average in three-dimensions given a user-defined definition of the cross section.
  • CrackFrontNonlocalStressComputes the average stress normal to the crack face.
  • InteractionIntegralComputes the interaction integral, which is used to compute various fracture mechanics parameters at a crack tip, including KI, KII, KIII, and the T stress.
  • JIntegralComputes the J-Integral, a measure of the strain energy release rate at a crack tip, which can be used as a criterion for fracture growth. It can, alternatively, compute the C(t) integral
  • LineMaterialRankTwoSamplerAccess a component of a RankTwoTensor
  • LineMaterialRankTwoScalarSamplerCompute a scalar property of a RankTwoTensor
  • MixedModeEquivalentKComputes the mixed-mode stress intensity factor given the , , and stress intensity factors
  • Phase Field App
  • EulerAngleUpdaterCheckProvide updated Euler angles after rigid body rotation of the grains.
  • FeatureVolumeVectorPostprocessorThis object is designed to pull information from the data structures of a "FeatureFloodCount" or derived object (e.g. individual feature volumes)
  • GrainForcesPostprocessorOutputs the values from GrainForcesPostprocessor
  • GrainTextureVectorPostprocessorGives out info on the grain boundary properties
  • Heat Transfer App
  • SurfaceRadiationVectorPostprocessorVectorPostprocessor for accessing information stored in surface radiation user object
  • ViewfactorVectorPostprocessorVectorPostprocessor for accessing view factors from GrayLambertSurfaceRadiationBase UO

Available Actions