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spectrum.h
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96 lines (72 loc) · 1.99 KB
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//
// Copyright 2018 The Simons Foundation, Inc. - All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#ifndef __ITENSOR_SPECTRUM_H
#define __ITENSOR_SPECTRUM_H
#include "itensor/tensor/vec.h"
#include "itensor/qn.h"
namespace itensor {
//
// Spectrum
//
// Stores density matrix eigenvalue spectrum following a call to
// svd, denmatDecomp, etc.
//
class Spectrum
{
public:
using QNStorage = std::vector<QN>;
private:
Vector eigs_;
Real truncerr_;
QNStorage qns_;
public:
Spectrum(Args const& args = Args::global());
Spectrum(Vector && eigs, Args const& args = Args::global());
Spectrum(Vector && eigs,
QNStorage && qns,
Args const& args = Args::global());
Real
truncerr() const { return truncerr_; }
Vector const&
eigs() const { return eigs_; }
Vector const&
eigsKept() const { return eigs(); }
//1-indexed
Real
eig(int n) const { return eigs_(n-1); }
int
numEigsKept() const { return eigs_.size(); }
bool
hasQNs() const { return !qns_.empty(); }
//1-indexed
QN
qn(int n) const;
QNStorage const&
qns() const { return qns_; }
int
size() const { return eigs_.size(); }
void
read(std::istream& s);
void
write(std::ostream& s) const;
private:
void
computeTruncerr(Args const& args);
}; //class Spectrum
std::ostream&
operator<<(std::ostream & s,Spectrum const& spec);
} //namespace itensor
#endif