// Compute the sign of the config from scratch
void Configuration::update_Sign() {
int s =0;
vector<int> n_op_with_a(Na,0), n_op_with_dag_a(Na,0);
// In this first part we compute the sign to bring the configuration to
// d^_1 d^_1 d^_1 ... d_1 d_1 d_1 d^_2 d^_2 ... d_2 d_2 ... d^_n .. d_n
// loop over the operators "op" in the trace (right to left)
for (Configuration::OP_REF op = DT.OpRef_begin(); ! op.atEnd(); ++op) {
// the info of the operator in "op"
BlockInfo op_info(info[op->Op->Number]);
// Check
if ((op_info.a == -1) && (op->Op->Statistic != Hloc::Operator::Bosonic))
TRIQS_RUNTIME_ERROR<<"Sign Computation : Operators must be fundamental or bosonic !!";
//DEBUG. check fundamental ops.
if (op_info.a != -1) assert (op->Op->Statistic == Hloc::Operator::Fermionic);
// Skip the bosonic operator in the sign computation
if (op->Op->Statistic == Hloc::Operator::Bosonic) continue;
// how many operators with a smaller a than "op" are there on the right of "op"?
for (int a = 0; a < op_info.a; a++) s += n_op_with_a[a];
n_op_with_a[op_info.a]++;
// if "op" is not a dagger how many operators of the same a but with a dagger are there on his right?
if (!op_info.dagger)
s += n_op_with_dag_a[op_info.a];
else
n_op_with_dag_a[op_info.a]++;
}
// Now we compute the sign to bring the configuration to
// d_1 d^_1 d_1 d^_1 ... d_1 d^_1 ... d_n d^_n ... d_n d^_n
for (int a = 0; a < Na; a++) {
int n = dets[a]->NumberOfC();
s += n*(n+1)/2;
}
OldSign = CurrentSign;
CurrentSign = (s%2==0 ? 1 : -1);
}
mc_weight_type Try() {
det = Config.dets[a_level];
// NB the det pointer has to be recomputed each time, since global moves will change it
#ifdef DEBUG
std::cout << "I AM IN Try for Insert_Cdag_C_Delta_SegmentPicture" << std::endl;
std::cout << "CONFIG BEFORE: " << Config.DT << std::endl;
// for (int a = 0; a<Config.Na; ++a) print_det(Config.dets[a]);
#endif
// Pick up a time to insert the first operator
double tau1 = Random(Config.Beta);
// Now find the operator A on the same a level at later time, with cyclicity
// and compute the maximal *oriented* length between the 2 operators (with cyclicity)
Configuration::OP_REF A;
if (det->size()>0) { // non empty
Configuration::DET_TYPE::Cdagger_iterator itCdag = det->Cdagger_begin();
Configuration::DET_TYPE::C_iterator itC = det->C_begin();
while ( (itCdag != det->Cdagger_end()) && (itCdag->tau > tau1) ) {++itCdag;}
while ( (itC != det->C_end()) && (itC->tau > tau1) ) {++itC;}
if (itCdag != det->Cdagger_begin()) --itCdag; else itCdag = --det->Cdagger_end();
if (itC != det->C_begin()) --itC; else itC = --det->C_end();
double rC = Config.CyclicOrientedTimeDistance((*itC)->tau - tau1);
double rCdag = Config.CyclicOrientedTimeDistance((*itCdag)->tau - tau1);
A = ( rC > rCdag ? *itCdag : * itC);
try_insert_length_max = min(rC,rCdag);
}
else { // empty case.
try_insert_length_max = Config.Beta;
A = Config.DT.OpRef_end();
}
// pick up the actual segment length
double rr= Random(try_insert_length_max-2*EPSILON) + EPSILON;
// deduce the time of the second operator
double tau2 = Config.CyclicOrientedTimeDistance(tau1 + rr);
// record the length of the kinks
if (Config.RecordStatisticConfigurations) {
deltaTau = Config.CyclicOrientedTimeDistance(tau2 - tau1);
HISTO_Length_Kinks_Proposed<< abs(deltaTau);
}
// Choose the operators to be inserted
const Hloc::Operator
& OpCdag(*Config.CdagOps[a_level][0]),
& OpC(*Config.COps[a_level][0]);
// shall we add C^+ C or C C^+
// we look whether the next operator is a dagger
bool Op1_is_dagger = true;
if (!A.atEnd()) {
const Configuration::BlockInfo & INFO(Config.info[A->Op->Number]);
assert(INFO.isFundamental());
Op1_is_dagger = INFO.dagger;
}
// Insert the operators Op1 and Op2.
// O1 will always be the dagger :
// Cf doc of insertTwoOperators, order of output OPREF is the same as input operators
Configuration::OP_REF O1, O2;
tie (no_trivial_reject,O1,O2) = (Op1_is_dagger ?
Config.DT.insertTwoOperators(tau1,OpCdag,tau2,OpC) :
Config.DT.insertTwoOperators(tau2,OpCdag,tau1,OpC));
if (!no_trivial_reject) return 0;
double tauCdag = (Op1_is_dagger ? tau1 : tau2);
double tauC = (Op1_is_dagger ? tau2 : tau1);
// Find the position for insertion in the determinant
// NB : the determinant store the C in decreasing order.
int numCdag=1;
for (Configuration::DET_TYPE::Cdagger_iterator p= det->Cdagger_begin();
(p != det->Cdagger_end()) && (p->tau > tauCdag) ; ++p, ++numCdag) {}
int numC=1;
for (Configuration::DET_TYPE::C_iterator p= det->C_begin();
(p != det->C_end()) && (p->tau > tauC) ; ++p, ++numC) {}
// acceptance probability
mc_weight_type p = Config.DT.ratioNewTrace_OldTrace() * det->try_insert(numCdag-1,numC-1,O1,O2);
int Na(det->size()+1);
// !!! det not modified until det->complete_operation is called, so I need to compensate by +1
double Tratio = Config.Beta * try_insert_length_max / (Na ==1 ? 1 : 2*Na);
// (Na... term : cf remove move...
#ifdef DEBUG
std::cout << "Trace Ratio: " << Config.DT.ratioNewTrace_OldTrace() << std::endl;
std::cout << "p*T: " << p*Tratio << std::endl;
std::cout << "CONFIG AFTER: " << Config.DT << std::endl;
//for (int a = 0; a<Config.Na; ++a) print_det(Config.dets[a]);
#endif
return p*Tratio;
}