https://github.com/ITensor/ITensor
Tip revision: df7298d7d614da776af548319ab4f9bbe344e8ab authored by Miles Stoudenmire on 09 September 2016, 02:58:02 UTC
Added optional names S+ and S- to tJ site set
Added optional names S+ and S- to tJ site set
Tip revision: df7298d
qn.h
//
// Distributed under the ITensor Library License, Version 1.2
// (See accompanying LICENSE file.)
//
#ifndef __ITENSOR_QN_H
#define __ITENSOR_QN_H
#include "itensor/global.h"
#include "itensor/arrow.h"
namespace itensor {
//
// QN
//
// Quantum number label for IQIndexes.
//
class QN;
//
// QN convenience accessor functions
//
//Get the Sz value
//Appropriate for QNs constructed via:
//spin, spinboson, electron, elparity
int
Sz(QN const& q);
//Get the Nb (boson number) value
//Appropriate for QNs constructed via:
//boson, spinboson
int
Nb(QN const& q);
//Get the Nf (fermion number) value
//Appropriate for QNs constructed via:
//electron
int
Nf(QN const& q);
//Get the fermion parity value.
//Either 0 for even parity or 1 for odd parity.
//Appropriate for QNs constructed via:
//electron, elparity
int
Pf(QN const& q);
//Nfp is an alias for Pf
int
Nfp(QN const& q);
size_t inline constexpr
QNSize() { return 4ul; }
//QNVal: storage element type for QN
//Represents a number with a Z (integer)
//or Z_M (integer mod M) addition rule
//
// Meaning of mod field:
// mod == 1 => Z addition
// mod > 1 => Z_M addition
// mod < 0 => same as above, fermionic
// mod == 0 => inactive/not used
struct QNVal
{
using qn_t = int;
private:
qn_t val_ = 0,
mod_ = 0;
public:
QNVal() { }
QNVal(qn_t v) : val_(v), mod_(1) { }
QNVal(qn_t v, qn_t m) : mod_(m) { set(v); }
QNVal(std::initializer_list<qn_t> qv)
{
if(qv.size() != 2) Error("initializer_list arg to QNVal must have two elements");
mod_ = *(qv.begin()+1);
set(*(qv.begin()));
}
qn_t
mod() const { return mod_; }
qn_t
val() const { return val_; }
void
set(qn_t v);
QNVal&
operator-() { set(-val_); return *this; }
};
//
// QN - quantum number label for IQIndex sectors
//
class QN
{
public:
using qn_t = QNVal::qn_t;
using storage_type = std::array<QNVal,QNSize()>;
using iterator = storage_type::iterator;
using const_iterator = storage_type::const_iterator;
private:
storage_type qn_{};
public:
QN() { }
// Takes named Args:
// QN({"Sz=",-1,"Nf=",2})
explicit
QN(Args const& args);
explicit
QN(qn_t q0);
QN(qn_t q0,
qn_t q1);
QN(qn_t q0,
qn_t q1,
qn_t q2);
QN(qn_t q0,
qn_t q1,
qn_t q2,
qn_t q3);
template <typename T, typename... Rest>
QN(const char* name1,
T const& t1,
Rest const&... rest)
: QN(Args(name1,t1,rest...))
{ }
// Takes QNVal arguments,
// specifying both a qn value in each
// sector and a mod factor
// Can call as as QN({0,2},{1,2})
explicit
QN(QNVal v0,
QNVal v1 = QNVal{},
QNVal v2 = QNVal{},
QNVal v3 = QNVal{})
: qn_{{v0,v1,v2,v3}}
{ }
explicit
QN(std::initializer_list<qn_t> qv)
{
qn_[0] = qv;
}
explicit operator bool() const { return qn_.front().mod() != 0; }
qn_t
operator[](size_t n) const
{
#ifdef DEBUG
return qn_.at(n).val();
#else
return qn_[n].val();
#endif
}
//1-indexed
qn_t
operator()(size_t n) const { return operator[](n-1); }
//1-indexed
qn_t
mod(size_t n) const { return qn_.at(n-1).mod(); }
size_t
size() const { return qn_.size(); }
//0-indexed
QNVal &
val0(size_t n)
{
#ifdef DEBUG
return qn_.at(n);
#else
return qn_[n];
#endif
}
//0-indexed
QNVal const&
val0(size_t n) const
{
#ifdef DEBUG
return qn_.at(n);
#else
return qn_[n];
#endif
}
void
modAssign(QN const& qo);
storage_type &
store() { return qn_; }
storage_type const&
store() const { return qn_; }
};
//
// QNVal functions
//
bool inline
isFermionic(QNVal const& qv) { return qv.mod() < 0; }
bool inline
isActive(QNVal const& qv) { return qv.mod() != 0; }
void
operator+=(QNVal& qva, QNVal const& qvb);
void
operator-=(QNVal& qva, QNVal const& qvb);
void
operator*=(QNVal& qva, Arrow dir);
bool
operator==(QNVal const& qva, QNVal const& qvb);
bool
operator!=(QNVal const& qva, QNVal const& qvb);
void
read(std::istream & s, QNVal & q);
void
write(std::ostream & s, QNVal const& q);
//
// QN functions
//
//1-indexed
bool inline
isActive(QN const& q, size_t n) { return isActive(q.val0(n-1)); }
bool inline
isFermionic(QN const& q, size_t n) { return q.mod(n) < 0; }
bool
operator==(QN const& qa, QN const& qb);
bool inline
operator!=(QN const& qa, QN const& qb) { return !operator==(qa,qb); }
bool
operator<(QN const& qa, QN const& qb);
QN
operator-(QN q);
void
operator+=(QN & qa, QN const& qb);
void
operator-=(QN & qa, QN const& qb);
void
operator*=(QN & qa, Arrow dir);
QN inline
operator+(QN qa, QN const& qb) { qa += qb; return qa; }
QN inline
operator-(QN qa, QN const& qb) { qa -= qb; return qa; }
QN inline
operator*(QN q, Arrow dir) { q *= dir; return q; }
QN inline
operator*(Arrow dir, QN q) { q *= dir; return q; }
std::ostream&
operator<<(std::ostream & s, QN const& q);
//returns -1 if any sector of the QN is fermionic and odd-parity
//otherwise returns +1
int
paritySign(QN const& q);
//returns true if any sector of the QN is fermionic
bool
isFermionic(QN const& q);
void
read(std::istream & s, QN & q);
void
write(std::ostream & s, QN const& q);
void
printFull(QN const& q);
int inline
Sz(QN const& q) { return q[0]; }
int inline
Nb(QN const& q) { return isActive(q,2) ? q(2) : q(1); }
int inline
Nf(QN const& q) { return isActive(q,2) ? q(2) : q(1); }
int inline
Pf(QN const& q) { return Nf(q)%2; }
int inline
Nfp(QN const& q) { return Pf(q); }
} //namespace itensor
#endif