Description

Base class for representing objects that introduce 'variables' (also referred as 'v') and their associated mass submatrices for a sparse representation of the problem.

See ChSystemDescriptor for more information about the overall problem and data representation.

Each ChVariables object must be able to compute a mass submatrix, that will be assembled directly inside the global matrix Z, (in particular inside the block H or M). Because of this there is no need for ChVariables and derived classes to actually store their mass submatrix in memory: they just need to be able to compute it!

Moreover, in some cases, the mass submatrix is not even needed. In fact, some Chrono solvers are matrix-free. This means that each ChVariables (and derived) object can be asked not to assemble its mass submatrix, but instead to provide operation related to it. E.g. M*x, M\x, +=M*x, and so on... Each derived class must implement these methods!

Because of this, the ChVariables class does not include any mass submatrix by default

#include <ChVariables.h>

Inheritance diagram for chrono::ChVariables:

[legend]

Public Member Functions
	ChVariables (int m_ndof)

ChVariables &	operator= (const ChVariables &other)
	Assignment operator: copy from other object.

void	SetDisabled (bool mdis)
	Deactivates/freezes the variable (these variables won't be modified by the system solver).

bool	IsDisabled () const
	Check if the variables have been deactivated (these variables won't be modified by the system solver).

bool	IsActive () const
	Check if these variables are currently active. More...

virtual int	Get_ndof () const
	The number of scalar variables in the vector qb (dof=degrees of freedom) *** This function MUST BE OVERRIDDEN by specialized inherited classes.

ChVectorRef	Get_qb ()
	Returns reference to qb, body-relative part of degrees of freedom q in system: More...

virtual void	Compute_fb ()
	Compute fb, body-relative part of known vector f in system. More...

ChVectorRef	Get_fb ()
	Returns reference to fb, body-relative part of known vector f in system. More...

virtual void	Compute_invMb_v (ChVectorRef result, ChVectorConstRef vect) const =0
	Computes the product of the inverse mass matrix by a vector, and store in result: result = [invMb]*vect.

virtual void	Compute_inc_invMb_v (ChVectorRef result, ChVectorConstRef vect) const =0
	Computes the product of the inverse mass matrix by a vector, and increment result: result += [invMb]*vect.

virtual void	Compute_inc_Mb_v (ChVectorRef result, ChVectorConstRef vect) const =0
	Computes the product of the mass matrix by a vector, and increment result: result = [Mb]*vect.

virtual void	MultiplyAndAdd (ChVectorRef result, ChVectorConstRef vect, const double c_a) const =0
	Computes the product of the corresponding block in the system matrix (ie. More...

virtual void	DiagonalAdd (ChVectorRef result, const double c_a) const =0
	Add the diagonal of the mass matrix scaled by c_a, to 'result', as a vector. More...

virtual void	Build_M (ChSparseMatrix &storage, int insrow, int inscol, const double c_a)=0
	Build the mass submatrix (for these variables) multiplied by c_a, storing it in 'storage' sparse matrix, at given column/row offset. More...

void	SetOffset (int moff)
	Set offset in global q vector (set automatically by ChSystemDescriptor)

int	GetOffset () const
	Get offset in global q vector.

virtual void	ArchiveOUT (ChArchiveOut &marchive)

virtual void	ArchiveIN (ChArchiveIn &marchive)

Protected Attributes
int	offset
	offset in global q state vector (needed by some solvers)

Member Function Documentation

◆ Build_M()

virtual void chrono::ChVariables::Build_M	(	ChSparseMatrix &	storage,
		int	insrow,
		int	inscol,
		const double	c_a
	)

pure virtual

Build the mass submatrix (for these variables) multiplied by c_a, storing it in 'storage' sparse matrix, at given column/row offset.

Most iterative solvers don't need to know this matrix explicitly. *** This function MUST BE OVERRIDDEN by specialized inherited classes

Implemented in chrono::ChVariablesBodySharedMass, chrono::ChVariablesShaft, chrono::ChVariablesBodyOwnMass, chrono::ChVariablesGeneric, chrono::ChVariablesNode, and chrono::ChVariablesGenericDiagonalMass.

◆ Compute_fb()

virtual void chrono::ChVariables::Compute_fb ( )

inlinevirtual

Compute fb, body-relative part of known vector f in system.

*** This function MAY BE OVERRIDDEN by specialized inherited classes (e.g., for impulsive multibody simulation, this may be fb = dt*Forces+[M]*previous_v ). Another option is to set values into fb vectors, accessing them by Get_fb() from an external procedure, for each body, before starting the solver.

◆ DiagonalAdd()

virtual void chrono::ChVariables::DiagonalAdd	(	ChVectorRef	result,
		const double	c_a
	)		const

pure virtual

Add the diagonal of the mass matrix scaled by c_a, to 'result', as a vector.

NOTE: the 'result' vector must already have the size of system unknowns, ie the size of the total variables & constraints in the system; the procedure will use the ChVariable offset (that must be already updated) as index.

Implemented in chrono::ChVariablesBodySharedMass, chrono::ChVariablesShaft, chrono::ChVariablesBodyOwnMass, chrono::ChVariablesGeneric, chrono::ChVariablesNode, and chrono::ChVariablesGenericDiagonalMass.

◆ Get_fb()

ChVectorRef chrono::ChVariables::Get_fb ( )

inline

Returns reference to fb, body-relative part of known vector f in system.

   | M -Cq'|*|q|- | f|= |0| ,  c>0, l>0, l*r=0;
   | Cq  0 | |l|  |-b|  |c|

This function can be used to set values of fb vector before starting the solver.

◆ Get_qb()

ChVectorRef chrono::ChVariables::Get_qb ( )

inline

Returns reference to qb, body-relative part of degrees of freedom q in system:

   | M -Cq'|*|q|- | f|= |0| ,  c>0, l>0, l*r=0;
   | Cq  0 | |l|  |-b|  |c|

◆ IsActive()

bool chrono::ChVariables::IsActive ( ) const

inline

Check if these variables are currently active.

In general, tells if they must be included into the system solver or not.

◆ MultiplyAndAdd()

virtual void chrono::ChVariables::MultiplyAndAdd	(	ChVectorRef	result,
		ChVectorConstRef	vect,
		const double	c_a
	)		const

pure virtual

Computes the product of the corresponding block in the system matrix (ie.

the mass matrix) by 'vect', scale by c_a, and add to 'result'. NOTE: the 'vect' and 'result' vectors must already have the size of the total variables&constraints in the system; the procedure will use the ChVariable offset (that must be already updated) to know the indexes in result and vect.

Implemented in chrono::ChVariablesBodySharedMass, chrono::ChVariablesShaft, chrono::ChVariablesBodyOwnMass, chrono::ChVariablesGeneric, chrono::ChVariablesNode, and chrono::ChVariablesGenericDiagonalMass.

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

/builds/uwsbel/chrono/src/chrono/solver/ChVariables.h
/builds/uwsbel/chrono/src/chrono/solver/ChVariables.cpp

Description

Public Member Functions

Protected Attributes

Member Function Documentation

◆ Build_M()

◆ Compute_fb()

◆ DiagonalAdd()

◆ Get_fb()

◆ Get_qb()

◆ IsActive()

◆ MultiplyAndAdd()