operations_research::LatticeMemoryManager< Set, CostType > Class Template Reference

Detailed Description

template<typename Set, typename CostType>
class operations_research::LatticeMemoryManager< Set, CostType >

The Dynamic Programming (DP) algorithm memorizes the values f(set, node) for node in set, for all the subsets of cardinality <= max_card_.

LatticeMemoryManager manages the storage of f(set, node) so that the DP iteration access memory in increasing addresses.

Definition at line 291 of file hamiltonian_path.h.

Public Member Functions
	LatticeMemoryManager ()
void	Init (int max_card)
	Reserves memory and fills in the data necessary to access memory. More...
uint64	Offset (Set s, int node) const
	Returns the offset in memory for f(s, node), with node contained in s. More...
uint64	BaseOffset (int card, Set s) const
	Returns the base offset in memory for f(s, node), with node contained in s. More...
uint64	OffsetDelta (int card, int added_node, int removed_node, int rank) const
	Returns the offset delta for a set of cardinality 'card', to which node 'removed_node' is replaced by 'added_node' at 'rank'. More...
void	SetValue (Set s, int node, CostType value)
	Memorizes the value = f(s, node) at the correct offset. More...
void	SetValueAtOffset (uint64 offset, CostType value)
	Memorizes 'value' at 'offset'. More...
CostType	Value (Set s, int node) const
	Returns the memorized value f(s, node) with node in s. More...
CostType	ValueAtOffset (uint64 offset) const
	Returns the memorized value at 'offset'. More...

Constructor & Destructor Documentation

LatticeMemoryManager()

template<typename Set, typename CostType>

operations_research::LatticeMemoryManager< Set, CostType >::LatticeMemoryManager ( )

inline

Definition at line 293 of file hamiltonian_path.h.

Member Function Documentation

BaseOffset()

template<typename Set, typename CostType >

uint64 operations_research::LatticeMemoryManager< Set, CostType >::BaseOffset ( int  card, Set  s  ) const

inline

Returns the base offset in memory for f(s, node), with node contained in s.

This is useful in the Dynamic Programming iterations. Note(user): inlining this function gains about 5%.

Todo:

(user): Investigate how to compute BaseOffset(card - 1, s \ { n }) from BaseOffset(card, n) to speed up the DP iteration.

There are binomial_coefficients_[node][node_rank + 1] sets which have node at node_rank.

Note(user): It is possible to get rid of base_offset_[card] by using a 2-D array. It would also make it possible to free all the memory but the layer being constructed and the preceding one, if another lattice of paths is constructed.

Todo:

(user): Evaluate the interest of the above. There are 'card' f(set, j) to store. That is why we need to multiply local_offset by card before adding it to the corresponding base_offset_.

Definition at line 407 of file hamiltonian_path.h.

Init()

template<typename Set , typename CostType >

void operations_research::LatticeMemoryManager< Set, CostType >::Init

(

int

max_card

)

Reserves memory and fills in the data necessary to access memory.

Initialize binomial_coefficients_ using Pascal's triangle recursion.

Extend to (n, n + 1) to minimize branchings in LatticeMemoryManager(). This also makes the recurrence above work for k = n.

There are k * binomial_coefficients_[max_card_][k] f(S,j) values to store for each group of f(S,j), with card(S) = k. Update base_offset[k] accordingly.

Definition at line 357 of file hamiltonian_path.h.

Offset()

template<typename Set, typename CostType >

uint64 operations_research::LatticeMemoryManager< Set, CostType >::Offset	(	Set	s,
		int	node
	)		const

Returns the offset in memory for f(s, node), with node contained in s.

Definition at line 431 of file hamiltonian_path.h.

OffsetDelta()

template<typename Set, typename CostType>

uint64 operations_research::LatticeMemoryManager< Set, CostType >::OffsetDelta ( int  card, int  added_node, int  removed_node, int  rank  ) const

inline

Returns the offset delta for a set of cardinality 'card', to which node 'removed_node' is replaced by 'added_node' at 'rank'.

Definition at line 310 of file hamiltonian_path.h.

SetValue()

template<typename Set, typename CostType>

void operations_research::LatticeMemoryManager< Set, CostType >::SetValue	(	Set	s,
		int	node,
		CostType	value
	)

Memorizes the value = f(s, node) at the correct offset.

This is favored in all other uses than the Dynamic Programming iterations.

Definition at line 443 of file hamiltonian_path.h.

SetValueAtOffset()

template<typename Set, typename CostType>

void operations_research::LatticeMemoryManager< Set, CostType >::SetValueAtOffset ( uint64  offset, CostType  value  )

inline

Memorizes 'value' at 'offset'.

This is useful in the Dynamic Programming iterations where we want to avoid compute the offset of a pair (set, node).

Definition at line 323 of file hamiltonian_path.h.

Value()

template<typename Set, typename CostType >

CostType operations_research::LatticeMemoryManager< Set, CostType >::Value	(	Set	s,
		int	node
	)		const

Returns the memorized value f(s, node) with node in s.

This is favored in all other uses than the Dynamic Programming iterations.

Definition at line 437 of file hamiltonian_path.h.

ValueAtOffset()

template<typename Set, typename CostType>

CostType operations_research::LatticeMemoryManager< Set, CostType >::ValueAtOffset ( uint64  offset ) const

inline

Returns the memorized value at 'offset'.

This is useful in the Dynamic Programming iterations.

Definition at line 333 of file hamiltonian_path.h.

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

• hamiltonian_path.h