syten::MPS::Operator Class Reference

Matrix Product Operator. More...

#include <operator.h>

Inheritance diagram for syten::MPS::Operator:

Collaboration diagram for syten::MPS::Operator:

Public Member Functions
MemoryUsage::MemorySize	allocSize () const
	allocSize() support More...
void	dropUnmatched ()
	Sweeps left-to-right and right-to-left over the MPO and drops unmatched blocks. More...
void	dropUnmatched (Index const site)
	Drop blocks in tensor on specified site which have no counterparts to the right/left. More...
bool	isIdentity () const
	Returns true if *this is an identity operator. More...
bool	isSingleSite () const
	Returns true if *this is a single-site operator. More...
	Operator ()=default
	Default ctor to initialise from archives. More...
	Operator (Index length)
	Standard ctor. More...
Tensor< 4 > &	operator() (Index const site)
	Access tensor on specified site. More...
Tensor< 4 > const &	operator() (Index const site) const
	Access tensor on specified site. More...
Operator &	operator*= (Operator const &other)
	Product of two operators, \( \hat O \; \hat T \), *this will be applied first to the state. More...
Operator &	operator*= (SDef const c)
	Product of a scalar and an operator, \( c \hat O \). More...
Operator &	operator+= (Operator const &other)
	Sum of two MPO, \( \hat O + \hat P \). More...
Operator &	operator-= (Operator const &other)
	Difference between two MPO, \( \hat O - \hat P \). More...
SRDef	project (Sector const &sector)
	Projects the operator onto the given symmetry sector. More...
template<typename Archive >
void	serialize (Archive &ar, const unsigned int in_version)
	Boost archiving. More...
Index	singleSite () const
	Returns the site on which the single-site operator acts if isSingleSite() is true, otherwise returns 0. More...
SRDef	truncate (TruncationType const &type=TruncationType::Default, bool verbose=false, SRDef const threshold=NAN, bool const nowarn=false)
	Truncates the operator by applying the specified truncation method on every site. More...
SRDef	truncate_mult_to_left (Index const site, TruncationType const &type, SRDef const threshold)
	Applies the specified truncation method on site position and multiplies the remainder into the next site to the left (use during right-to-left sweep). More...
SRDef	truncate_mult_to_right (Index const site, TruncationType const &type, SRDef const threshold)
	Applies the specified truncation method on site position and multiplies the remainder into the next site to the right (use during left-to-right sweep). More...
Public Member Functions inherited from std::vector< Tensor< 4 > >
Tensor< 4 >	assign (Tensor< 4 > ... args)
Tensor< 4 >	at (Tensor< 4 > ... args)
Tensor< 4 >	back (Tensor< 4 > ... args)
Tensor< 4 >	begin (Tensor< 4 > ... args)
Tensor< 4 >	capacity (Tensor< 4 > ... args)
Tensor< 4 >	cbegin (Tensor< 4 > ... args)
Tensor< 4 >	cend (Tensor< 4 > ... args)
Tensor< 4 >	clear (Tensor< 4 > ... args)
Tensor< 4 >	crbegin (Tensor< 4 > ... args)
Tensor< 4 >	crend (Tensor< 4 > ... args)
Tensor< 4 >	data (Tensor< 4 > ... args)
Tensor< 4 >	emplace (Tensor< 4 > ... args)
Tensor< 4 >	emplace_back (Tensor< 4 > ... args)
Tensor< 4 >	empty (Tensor< 4 > ... args)
Tensor< 4 >	end (Tensor< 4 > ... args)
Tensor< 4 >	erase (Tensor< 4 > ... args)
Tensor< 4 >	front (Tensor< 4 > ... args)
Tensor< 4 >	get_allocator (Tensor< 4 > ... args)
Tensor< 4 >	insert (Tensor< 4 > ... args)
Tensor< 4 >	max_size (Tensor< 4 > ... args)
Tensor< 4 >	operator= (Tensor< 4 > ... args)
Tensor< 4 >	operator[] (Tensor< 4 > ... args)
Tensor< 4 >	pop_back (Tensor< 4 > ... args)
Tensor< 4 >	push_back (Tensor< 4 > ... args)
Tensor< 4 >	rbegin (Tensor< 4 > ... args)
Tensor< 4 >	rend (Tensor< 4 > ... args)
Tensor< 4 >	reserve (Tensor< 4 > ... args)
Tensor< 4 >	resize (Tensor< 4 > ... args)
Tensor< 4 >	shrink_to_fit (Tensor< 4 > ... args)
Tensor< 4 >	size (Tensor< 4 > ... args)
Tensor< 4 >	swap (Tensor< 4 > ... args)
Tensor< 4 >	vector (Tensor< 4 > ... args)
Tensor< 4 >	~vector (Tensor< 4 > ... args)

Public Attributes
int	is_sso {-1}
	if > -1, denotes the site of the sso, otherwise, that the tensor is not a single-site operator; if -2 denotes that this is an identity and will take on the SSO-ness of the other operator during multiplication! More...
Public Attributes inherited from std::vector< Tensor< 4 > >
Tensor< 4 >	elements
	STL member. More...

Static Public Attributes
static constexpr Index	dIdx {4}
	position of lower physical index in constituent tensors More...
static constexpr int	dInt {4}
	position of lower physical index in constituent tensors, int for prod specs More...
static const std::array< Direction, 4 >	dirs = {Direction::Inc, Direction::Out, Direction::Inc, Direction::Out}
	incoming/outgoing bases convention More...
static constexpr Index	lIdx {2}
	position of left MPO index in constituent tensors More...
static constexpr int	lInt {2}
	position of left MPO index in constituent tensors, int for prod specs More...
static constexpr Index	rIdx {1}
	position of right MPO index in constituent tensors More...
static constexpr int	rInt {1}
	position of right MPO index in constituent tensors, int for prod specs More...
static constexpr Index	uIdx {3}
	position of upper physical index in constituent tensors More...
static constexpr int	uInt {3}
	position of upper physical index in constituent tensors, int for prod specs More...
static constexpr unsigned int	version = 2
	Bump this if the above changes. More...

Private Member Functions
SRDef	truncate_impl (TruncationType const &type, Index max_sweeps=0, bool verbose=false, SRDef threshold=NAN, bool const nowarn=false)
	Actual implementation of the truncation, sweeps with the specified method until output dimensions don't change any longer if max_sweeps == 0 or until either max_sweeps have been done or the output dimension doesn't change any more. More...

Detailed Description

Matrix Product Operator.

Always kept entirely in RAM, as they tend not to be too big (even without symmetries at most just L³ (~ 2 GB for 512 sites) and typically 100 × L (~ 1 MB for 512 sites)).

Note on Order of Application

The order in which operators are applied to a state differ from the usual convention. That is:

State s; s *= op1; s *= op2;

first applies op1 and then op2 and is equivalent to

s = (s * op1); s = (s * op2);

which in turn is equivalent to

t = op1; t *= op2; s *= t;

and

s = s * (op1 * op2);

whereas in linear algebra one would expect the opposite ( \( \hat B \hat A \) first applying \( \hat A \), then \( \hat B \)).

If we tried the other convention, State *= Operator would either have to be removed or stick out and Operator =* State unfortunately doesn’t exist.

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

• inc/mps/operator.h
• inc/mps/operator.cpp