Parallelizable Handling of Output Data (analysisdata)

Collaboration diagram for Parallelizable Handling of Output Data (analysisdata):

Description

Provides functionality for handling and processing output data from analysis.

Overview

This module provides functionality to do common processing for tabular data in analysis tools. In addition to providing this common functionality, one major driver for this module is to make it simple to write analysis tools that process frames in parallel: the functionality in this module takes care of necessary synchronization and communication such that output from the frames is collected and output in the correct order. See Analysis output data handling for an overview of the high-level functionality and the terminology used.

This module consists of two main parts. The first is formed by the gmx::AbstractAnalysisData class and classes that derive from it: gmx::AnalysisData and gmx::AnalysisArrayData. These classes are used to process and store raw data as produced by the analysis tool. They also provide an interface to attach data modules that implement gmx::IAnalysisDataModule.

Modules that implement gmx::IAnalysisDataModule form the second part of the module, and they provide functionality to do processing on the data. These modules can also derive from gmx::AbstractAnalysisData, allowing other modules to be attached to them to form a processing chain that best suits the analysis tool. Typically, such a processing chain ends in a plotting module that writes the data into a file, but the final module can also provide direct access to the processed data, allowing the analysis tool to do custom postprocessing outside the module framework.

Using Data Objects and Modules

To use the functionality in this module, you typically declare one or more AnalysisData objects and set its properties. You then create some module objects and set their properties (see the list of classes that implement gmx::IAnalysisDataModule) and attach them to the data objects or to one another using gmx::AbstractAnalysisData::addModule(). Then you add the actual data values to the gmx::AnalysisData object, which automatically passes it on to the modules. After all data is added, you may optionally access some results directly from the module objects or from the gmx::AnalysisData object itself. However, in many cases it is sufficient to initially add a plotting module to the processing chain, which will then automatically write the results into a file.

For simple processing needs with a small amount of data, an gmx::AnalysisArrayData class is also provided, which keeps all the data in an in-memory array and allows you to manipulate the data as you wish before you pass the data to the attached modules.

Data Modules

Modules that derive from gmx::IAnalysisDataModule can operate in two modes:

• In serial mode, the frames are presented to the module always in the order of increasing indices, even if they become ready in a different order in the attached data.
• In parallel mode, the frames are presented in the order that they become available in the input data, which may not be sequential. This mode allows the input data to optimize its behavior if it does not need to store and sort the frames.

The figure below shows the sequence of callbacks that the module receives. Arrows show a dependency between callbacks: the event at the start of the arrow always occurs before the event at the end. The events in the box are repeated for each frame. Dashed lines within this box show dependencies between these frames:

• In serial mode, all the events are called in a deterministic order, with each frame completely processed before the next starts.
• In parallel mode, multiple frames can be in progress simultaneously, and the events for different frames can occur even concurrently on different threads. However, frameFinishSerial() events will always occur in deterministic, sequential order for the frames. Also, the number of concurrent frames is limited by the parallelization factor passed to parallelDataStarted(): only M frames after the last frame for which frameFinishSerial() has been called can be in progress

If the input data supports parallel mode, it calls parallelDataStarted(). If the module returns true from this method, then it will process the frames in the parallel mode. If the module returns false, it will get the frames in serial order. If the input data does not support parallel mode, it calls dataStarted(), and the module will always get the frames in order.

The sequence of when the module methods are called with respect to when data is added to the data object depends on the type of the module and the type of the data. However, generally the modules do not need to know the details of how this happens, as long as they work with the above state diagram.

For parallel processing, the gmx::AnalysisData object itself only provides the infrastructure to support all of the above, including the reordering of the frames for serial processing. However, the caller is still responsible of the actual thread synchronization, and must call gmx::AnalysisData::finishFrameSerial() for each frame from a suitable context where the serial processing for that frame can be done. When using the data objects as part of the trajectory analysis framework (Framework for trajectory analysis) or energy analysis framework (Framework for energy analysis), these calls are handled by the framework.

Author

Teemu Murtola teemu.nosp@m..mur.nosp@m.tola@.nosp@m.gmai.nosp@m.l.com

Classes
class	gmx::AbstractAnalysisData
	Abstract base class for all objects that provide data. More...
class	gmx::AnalysisData
	Parallelizable data container for raw data. More...
class	gmx::AnalysisDataHandle
	Handle for inserting data into AnalysisData. More...
class	gmx::AbstractAnalysisArrayData
	Abstract base class for data objects that present in-memory data. More...
class	gmx::AnalysisArrayData
	Simple in-memory data array. More...
class	gmx::AnalysisDataValue
	Value type for representing a single value in analysis data objects. More...
class	gmx::AnalysisDataFrameHeader
	Value type for storing frame-level information for analysis data. More...
class	gmx::AnalysisDataPointSetRef
	Value type wrapper for non-mutable access to a set of data column values. More...
class	gmx::AnalysisDataFrameRef
	Value type wrapper for non-mutable access to a data frame. More...
class	gmx::IAnalysisDataModule
	Interface for a module that gets notified whenever data is added. More...
class	gmx::AnalysisDataModuleSerial
	Convenience base class for serial analysis data modules. More...
class	gmx::AnalysisDataModuleParallel
	Convenience base class for parallel analysis data modules. More...
class	gmx::AnalysisDataAverageModule
	Data module for independently averaging each column in input data. More...
class	gmx::AnalysisDataFrameAverageModule
	Data module for averaging of columns for each frame. More...
class	gmx::AnalysisDataDisplacementModule
	Data module for calculating displacements. More...
class	gmx::AnalysisHistogramSettingsInitializer
	Provides "named parameter" idiom for constructing histograms. More...
class	gmx::AnalysisHistogramSettings
	Contains parameters that specify histogram bin locations. More...
class	gmx::AbstractAverageHistogram
	Base class for representing histograms averaged over frames. More...
class	gmx::AnalysisDataSimpleHistogramModule
	Data module for per-frame histograms. More...
class	gmx::AnalysisDataWeightedHistogramModule
	Data module for per-frame weighted histograms. More...
class	gmx::AnalysisDataBinAverageModule
	Data module for bin averages. More...
class	gmx::AnalysisDataLifetimeModule
	Data module for computing lifetime histograms for columns in input data. More...
class	gmx::AnalysisDataPlotSettings
	Common settings for data plots. More...
class	gmx::AbstractPlotModule
	Abstract data module for writing data into a file. More...
class	gmx::AnalysisDataPlotModule
	Plotting module for straightforward plotting of data. More...
class	gmx::AnalysisDataVectorPlotModule
	Plotting module specifically for data consisting of vectors. More...

Directories
directory	analysisdata
	Parallelizable Handling of Output Data (analysisdata)

Files
file	abstractdata.h
	Declares gmx::AbstractAnalysisData.
file	analysisdata.h
	Declares gmx::AnalysisData and gmx::AnalysisDataHandle.
file	arraydata.h
	Declares gmx::AbstractAnalysisArrayData and gmx::AnalysisArrayData.
file	dataframe.h
	Declares classes for accessing data frame information.
file	datamodule.h
	Declares gmx::IAnalysisDataModule and related convenience classes.
file	average.h
	Declares gmx::AnalysisDataAverageModule.
file	displacement.h
	Declares gmx::AnalysisDataDisplacementModule.
file	histogram.h
	Declares analysis data modules for calculating histograms.
file	lifetime.h
	Declares gmx::AnalysisDataLifetimeModule.
file	plot.h
	Declares gmx::AnalysisDataPlotModule for plotting data (into a file).