A vertex's exact (rational) position, stored only while it differs from the vertex's double position. More...

#include <ExactPosition.hpp>

Public Member Functions
	ExactPosition (const ExactPosition &o)

ExactPosition &	operator= (const ExactPosition &o)

VecR	value (const VecD &posf) const
	The exact position of a vertex whose double position is `posf`.

bool	coord_equals (int k, const VecD &posf, const Rational &r) const
	Whether coordinate `k` equals `r`, without materialising the whole position.

void	store (const VecR &p)
	Store an exact position that may differ from the double one.

void	clear ()
	The exact position is the double one: drop the stored copy.

bool	stored () const

Private Attributes
std::unique_ptr< VecR >	m_p

Detailed Description

template<class VecR, class VecD>
class wmtk::ExactPosition< VecR, VecD >

A vertex's exact (rational) position, stored only while it differs from the vertex's double position.

The optimizer meshes keep every vertex position twice: as doubles, which everything reads, and as rationals, which only the exact predicates read and only while a vertex cannot be rounded. Once a vertex is rounded its exact position IS its double position – the code keeps the two equal by construction – so the rational copy carries no information, yet it cost a Vector of GMP rationals per vertex slot: 32 bytes inline per coordinate plus heap limbs, roughly 290 bytes per 3D vertex and most of a vertex slot's footprint.

So the rational position lives behind a pointer that is null whenever it would equal the double one, and value() rebuilds it from the double position on demand. Reads see exactly the value they saw before; only vertices that are genuinely not representable in doubles (and the few that are mid-operation) pay for the rational storage.

Copying copies the stored position. There are deliberately no move operations: moving one of these copies it, as moving the Vector of Rationals it replaces did (Rational has no move constructor), so attribute slots moved from during consolidation keep their contents.

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

src/wmtk/ExactPosition.hpp

Public Member Functions

Private Attributes

Detailed Description