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#include "wolff.h"
v_t flip_cluster(ising_state_t *s, v_t v0, q_t step, gsl_rng *r) {
q_t s0 = s->spins[v0];
v_t nv = 0;
ll_t *stack = NULL; // create a new stack
stack_push(&stack, v0); // push the initial vertex to the stack
//node_t *T = NULL;
bool *marks = (bool *)calloc(s->g->nv, sizeof(bool));
while (stack != NULL) {
v_t v = stack_pop(&stack);
// if (!tree_contains(T, v)) { // if the vertex hasn't already been flipped
if (!marks[v]) {
q_t s_old = s->spins[v];
q_t s_new = (s->spins[v] + step) % s->q;
s->spins[v] = s_new; // flip the vertex
//tree_insert(&T, v);
marks[v] = true;
v_t nn = s->g->v_i[v + 1] - s->g->v_i[v];
for (v_t i = 0; i < nn; i++) {
v_t vn = s->g->v_adj[s->g->v_i[v] + i];
q_t sn = s->spins[vn];
double prob;
bool is_ext = (v == s->g->nv - 1 || vn == s->g->nv - 1);
q_t M_ind_0;
q_t M_ind_1;
if (is_ext) {
if (vn == s->g->nv - 1) {
M_ind_0 = (s_old + s->q - sn) % s->q;
M_ind_1 = (s_new + s->q - sn) % s->q;
} else {
M_ind_0 = (sn + s->q - s_old) % s->q;
M_ind_1 = (sn + s->q - s_new) % s->q;
}
prob = s->H_probs[M_ind_1 * s->q + M_ind_0];
s->M[M_ind_0]--;
s->M[M_ind_1]++;
s->E += - s->H[M_ind_1] + s->H[M_ind_0];
} else {
M_ind_0 = (s_old + s->q - sn) % s->q;
M_ind_1 = (s_new + s->q - sn) % s->q;
prob = s->J_probs[M_ind_1 * s->q + M_ind_0];
s->E += - s->J[M_ind_1] + s->J[M_ind_0];
}
if (gsl_rng_uniform(r) < prob) { // and with probability ps[e]...
stack_push(&stack, vn); // push the neighboring vertex to the stack
}
}
if (v != s->g->nv - 1) { // count the number of non-external sites that flip
nv++;
}
}
}
//tree_freeNode(T);
free(marks);
return nv;
}
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