array_8d<double> Nevpt2_npdm::compute_EEEE_matrix(array_2d<double>& onepdm, array_4d<double>& twopdm, array_6d<double>& threepdm, array_8d<double>& fourpdm)
{
if( mpigetrank() == 0 ) {
std::cout << "Building spatial <0|EEEE|0>\n";
int dim = threepdm.dim1();
assert( onepdm.dim1() == twopdm.dim1() );
array_8d<double> eeee_matrix(dim,dim,dim,dim,dim,dim,dim,dim);
eeee_matrix.Clear();
// Output text file
double factor = 1.0;
char file[5000];
sprintf (file, "%s%s%d.%d%s", dmrginp.save_prefix().c_str(),"/EEEE_matrix.", 0, 0,".txt");
ofstream ofs(file);
ofs << dim << endl;
for(int i=0; i<dim; ++i) {
for(int j=0; j<dim; ++j) {
for(int k=0; k<dim; ++k) {
int d_jk = ( j == k );
for(int l=0; l<dim; ++l) {
for(int m=0; m<dim; ++m) {
int d_lm = ( l == m );
int d_jm = ( j == m );
for(int n=0; n<dim; ++n) {
for(int p=0; p<dim; ++p) {
int d_np = ( n == p );
int d_lp = ( l == p );
int d_jp = ( j == p );
for(int q=0; q<dim; ++q) {
double val = 0.0;
// 1PDM terms
val += d_jk * d_lm * d_np * onepdm(i,q);
// 2PDM terms
val += d_jk * d_lm * 2.0*twopdm(i,p,q,n); // Note factor of two difference between Block 2PDMs and other codes
val += d_jk * d_np * 2.0*twopdm(i,m,q,l);
val += d_jk * d_lp * 2.0*twopdm(i,m,n,q);
val += d_jm * d_np * 2.0*twopdm(i,k,l,q);
val += d_jm * d_lp * 2.0*twopdm(i,k,q,n);
val += d_lm * d_np * 2.0*twopdm(i,k,q,j);
val += d_lm * d_jp * 2.0*twopdm(i,k,n,q);
// 3PDM terms
val += d_jk * threepdm(i,m,p,q,n,l);
val += d_jm * threepdm(i,k,p,q,l,n);
val += d_lm * threepdm(i,k,p,q,n,j);
val += d_np * threepdm(i,k,m,q,l,j);
val += d_lp * threepdm(i,k,m,n,q,j);
val += d_jp * threepdm(i,k,m,n,l,q);
// 4PDM terms
val += fourpdm(i,k,m,p,j,l,n,q);
if ( abs(val) > 1e-14 ) {
ofs << boost::format("%d %d %d %d %d %d %d %d %20.14e\n") % i % j % k % l % m % n % p % q % val;
eeee_matrix(i,j,k,l,m,n,p,q) = val;
}
}
}
}
}
}
}
}
}
ofs.close();
// Save binary matrix
sprintf (file, "%s%s%d.%d%s", dmrginp.save_prefix().c_str(),"/EEEE_matrix.", 0, 0,".bin");
std::ofstream ofs2(file, std::ios::binary);
boost::archive::binary_oarchive save(ofs2);
save << eeee_matrix;
ofs2.close();
return eeee_matrix;
}
}
