Base class for measurements of velocity autocorrelation in MPC fluids. More...

#include <Base.hpp>

Inheritance diagram for OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base:

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Collaboration diagram for OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base:

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Classes
class	Snapshot
	Represents a snapshot of the MPC fluid constituent velocities. More...

Public Member Functions
virtual	~Base ()
	The destructor. More...

void	measure ()
	Performs measurements. More...

void	save (const std::string &rundir) const
	Saves the data to the given run directory. More...

Static Public Member Functions
static bool	isConfigured (const Simulation *const sim)
	Returns whether the given simulation configured this instrumentation. More...

Protected Member Functions
	Base (const Simulation const sim, DeviceMemoryManager const devMemMgr, const MPCFluid::Base *const mpcFluid_, const unsigned int numberOfConstituents_)
	The constructor. More...

virtual void	populateCurrentVelocities ()=0
	Populates the Device buffer with the current velocities of the fluid constituents. More...

Protected Attributes
const Simulation *const	simulation
	The simulation instance. More...

DeviceMemoryManager *const	deviceMemoryManager
	The Device memory manager. More...

const MPCFluid::Base *const	mpcFluid
	The fluid to measure. More...

const unsigned int	numberOfConstituents
	The number of logical constituents (e.g. pairs, triplets, ...) in the fluid. More...

FP	measurementTime
	The maximum time between snapshots. More...

std::vector< Snapshot * >	snapshots
	The snapshots of the fluid constituent velocities. More...

MPCParticleVelocityType *	currentVelocities
	Current velocities of the fluid constituents. More...

std::deque< boost::tuple< FP, FP, MPCParticleVelocityType > >	autocorrelations
	Collection of tuples consisting of, in that order, \( t_i \), \( t_j \), and \( V \left( t_i, t_j \right) \). More...

Detailed Description

Base class for measurements of velocity autocorrelation in MPC fluids.

This class and its subclasses aid in measuring the velocity autocorrelation function of the fluid constituents' centers of mass, i.e.

\[ \left< \vec{v} \left( t \right) \cdot \vec{v} \left( 0 \right) \right> = \frac{ 1 }{ N_{\textrm{logical entites}} } \sum_{k = 0}^{N_{\textrm{logical entites}} - 1} \left< \vec{v}_k \left( t \right) \cdot \vec{v}_k \left( 0 \right) \right> \]

where \( N_{\textrm{logical entites}} \) is the number of logical entities in the fluid (see OpenMPCD::CUDA::MPCFluid::Base), \( \vec{v}_k \left( t \right) \) is the velocity of the center of mass of the logical entity with index \( k \) at simulation time \( t \), and the angle brackets denote expectation values.

To approximate this quantity, the center of mass velocities of the logical entities are stored in snapshots periodically. Then, each time measure is called, the quantity

\[ V \left( t_i, t \right) = \frac{ 1 }{ N_{\textrm{logical entites}} } \sum_{k = 0}^{N_{\textrm{logical entites}} - 1} \vec{v}_k \left( t_i \right) \cdot \vec{v}_k \left( t \right) \]

is calculated, i.e. the sample average of the inner product of a logical entity's center of mass velocity at the current time \( t \) with that same logical entity's center of mass velocity at snapshot time \( t_i \), for all currently available snapshots \( i \).

At most, snapshotCount (see configuration options below) many snapshots are stored at any point in time. Every time measure is called, before the \( V \left( t_i, t \right) \) are calculated as described above, the following procedure takes place:

If no snapshots have been taken yet, a snapshot it taken.
Otherwise, if fewer than snapshotCount snapshots have already been created, the latest snapshot time is subtracted from the current simulation time. If that difference is larger than measurementTime / snapshotCount - 1e-6, a new snapshot is taken and stored after the previously taken snapshot.
If there have already been snapshotCount many snapshots before the call to measure, all of the snapshots are iterated over. For each such snapshot, if the difference between the current simulation time and that snapshot's time is greater than measurementTime + 1e-6, that snapshot is overridden in place with the current state and simulation time. The order of snapshots in memory, as described above, is of consequence for the order in which measurements are written by the save function.

Given this, the velocity autocorrelation function \( \left< \vec{v} \left( t \right) \cdot \vec{v} \left( 0 \right) \right> \) can be approximated as the average of all \( V \left( t_i, t_j \right) \) where \( t_j - t_i = t \).

However, this last step is currently not performed by this class; instead, it computes \( V \left( t_i, t_j \right) \) and stores them, along with \( t_i \) and \( t_j \).

This class and its subclasses are configured via the instrumentation.velocityAutocorrelation configuration group, which consists of the following settings:

snapshotCount, a positive integer, determines the maximum number of snapshots stored in memory at any given time.
measurementTime, which is a floating-point value that is approximately the maximal time for which the correlation function is measured; see above for details.

Definition at line 110 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

Constructor & Destructor Documentation

◆ Base()

OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::Base	(	const Simulation *const	sim,
		DeviceMemoryManager *const	devMemMgr,
		const MPCFluid::Base *const	mpcFluid_,
		const unsigned int	numberOfConstituents_
	)

protected

The constructor.

Exceptions

OpenMPCD::InvalidConfigurationException	Throws if the configuration is invalid.
OpenMPCD::NULLPointerException	If `OPENMPCD_DEBUG` is defined, throws if any of the pointer arguments is a `nullptr`.
OpenMPCD::InvalidArgumentException	If `OPENMPCD_DEBUG` is defined, throws if `numberOfConstituents_ == 0`.

Parameters

[in]	sim	The simulation instance.
[in]	devMemMgr	The Device memory manager instance.
[in]	mpcFluid_	The MPC fluid to measure.
[in]	numberOfConstituents_	The number of logical constituents (e.g. pairs, triplets, ...) in the fluid.

◆ ~Base()

virtual OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::~Base ( )

virtual

The destructor.

Member Function Documentation

◆ isConfigured()

static bool OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::isConfigured ( const Simulation *const sim )

static

Returns whether the given simulation configured this instrumentation.

Parameters

[in] sim The simulation instance.

Exceptions

NULLPointerException Throws if sim is nullptr.

◆ measure()

void OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::measure ( )

Performs measurements.

◆ populateCurrentVelocities()

virtual void OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::populateCurrentVelocities ( )

protectedpure virtual

Populates the Device buffer with the current velocities of the fluid constituents.

Implemented in OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Chains, OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Doublets, OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Simple, and OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Triplets.

◆ save()

void OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::save ( const std::string & rundir ) const

Saves the data to the given run directory.

The given run directory is created if necessary, and so is the data file therein; if the data file already exists, it will be truncated.

Multiple lines will be written to the file, each consisting of three tab-separated columns: The first column corresponds to the simulation time \( t_i \) of a snapshot \( i \); the second column to the simulation time \( t_j \ge t_i \) ; and finally, the third column contains \( V \left( t_i, t_j \right) \). One such line will be written for every measured \( V \) (see class documentation for details).

The lines are ordered by ascending \( t_j \) first, and then by ascending snapshot position in memory (see class documentation for details).

Parameters

[in] rundir The path to the run directory. Within that directory, the data will be saved to the file velocityAutocorrelations.data.

Member Data Documentation

◆ autocorrelations

std::deque<boost::tuple<FP, FP, MPCParticleVelocityType> > OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::autocorrelations

protected

Collection of tuples consisting of, in that order, \( t_i \), \( t_j \), and \( V \left( t_i, t_j \right) \).

Definition at line 320 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ currentVelocities

MPCParticleVelocityType* OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::currentVelocities

protected

Current velocities of the fluid constituents.

Definition at line 318 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ deviceMemoryManager

DeviceMemoryManager* const OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::deviceMemoryManager

protected

The Device memory manager.

Definition at line 309 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ measurementTime

FP OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::measurementTime

protected

The maximum time between snapshots.

Definition at line 315 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ mpcFluid

const MPCFluid::Base* const OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::mpcFluid

protected

The fluid to measure.

Definition at line 310 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ numberOfConstituents

const unsigned int OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::numberOfConstituents

protected

The number of logical constituents (e.g. pairs, triplets, ...) in the fluid.

Definition at line 312 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ simulation

const Simulation* const OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::simulation

protected

The simulation instance.

Definition at line 308 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

◆ snapshots

std::vector<Snapshot*> OpenMPCD::CUDA::MPCFluid::Instrumentation::VelocityAutocorrelation::Base::snapshots

protected

The snapshots of the fluid constituent velocities.

Definition at line 317 of file CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp.

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

CUDA/MPCFluid/Instrumentation/VelocityAutocorrelation/Base.hpp

Classes

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Base()

◆ ~Base()

Member Function Documentation

◆ isConfigured()

◆ measure()

◆ populateCurrentVelocities()

◆ save()

Member Data Documentation

◆ autocorrelations

◆ currentVelocities

◆ deviceMemoryManager

◆ measurementTime

◆ mpcFluid

◆ numberOfConstituents

◆ simulation

◆ snapshots