read error : Wrong number of IndexVals passed to real/cplx

Question

I save the wave function given by dmrg using "writeToFile("output/psitest", psi)". And then I try to read it by using "readFromFile" and calculate correlation function, the error comes out. The code that reads psitest from file is

// this file tests spinless Bose-Hubbard model
#include "itensor/all.h"
#include <typeinfo>
#include <iostream>
#include <fstream>
#include <vector>
#include <stdlib.h>
#include <cmath>
#include <cstring>
#include <sstream>

using namespace itensor;
using namespace std;

int main()
{
  auto N = 40;
  auto sites = BH(N);

  auto psi = readFromFile<IQMPS>("psi_test");

  auto pos_i = int(N/4);
  auto pos_f = 3*int(N/4);
  auto AL = sites.op("Nb", pos_i);
  auto AR = sites.op("Nb", pos_f);
  psi.position(pos_i);

  auto C = psi.A(pos_i);
  C *= AL;
  auto iR = commonIndex(psi.A(pos_i), psi.A(pos_i+1), Link);
  C *= dag(prime(prime(psi.A(pos_i), Site), iR));
  for (int i = pos_i+1; i < pos_f; i++){
    C *= psi.A(i);
    C *= dag(prime(psi.A(i), Link));
  }
  C *= psi.A(pos_f);
  C *= AR;
  auto iL = commonIndex(psi.A(pos_f-1), psi.A(pos_f), Link);
  C *= dag(prime(prime(psi.A(pos_f), Site), iL));

  cout << C.real() << endl;

}  

In fact, there is no error if I do not use "C.real()" and this i should be the origin of the problem. I also try to calculated the same correlation function just after the "dmrg" immediately, that is, I do not save the "psi" and read it later. No problem appears.

Answer 1

I have solved this question. Here I present the correct version.

// this file tests spinless Bose-Hubbard model
#include "itensor/all.h"
#include <typeinfo>
#include <iostream>
#include <fstream>
#include <vector>
#include <stdlib.h>
#include <cmath>
#include <cstring>
#include <sstream>

using namespace itensor;
using namespace std;

int main()
{
  auto N = 40;
  BH sites;
  readFromFile("sites_test", sites);
  IQMPS psi(sites);
  readFromFile("psi_test", psi);

  // long-range correlation
  auto pos_i = int(N/4);
  auto pos_f = 3*int(N/4);
  auto AL = sites.op("Ab", pos_i);
  auto AR = sites.op("Adagb", pos_f);
  psi.position(pos_i);

  auto C = psi.A(pos_i);
  C *= AL;
  auto iR = commonIndex(psi.A(pos_i), psi.A(pos_i+1), Link);
  C *= dag(prime(prime(psi.A(pos_i), Site), iR));
  for (int i = pos_i+1; i < pos_f; i++){
    C *= psi.A(i);
    C *= dag(prime(psi.A(i), Link));
  }
  C *= psi.A(pos_f);
  C *= AR;
  auto iL = commonIndex(psi.A(pos_f-1), psi.A(pos_f), Link);
  C *= dag(prime(prime(psi.A(pos_f), Site), iL));

  cout << C.real() << endl;  

}  

Comments

Could you explain further what the error was and how you fixed it? Was it because you changed operators or because of the way you read the files?