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-rw-r--r--lib/wolff.h2
-rw-r--r--lib/wolff_tools.c8
2 files changed, 8 insertions, 2 deletions
diff --git a/lib/wolff.h b/lib/wolff.h
index 4270f33..428ce85 100644
--- a/lib/wolff.h
+++ b/lib/wolff.h
@@ -31,6 +31,8 @@ typedef struct {
int32_t dHb;
} cluster_t;
+int32_t sign(double x);
+
cluster_t *flip_cluster(const graph_t *g, const double *ps, bool *x,
gsl_rng *r);
diff --git a/lib/wolff_tools.c b/lib/wolff_tools.c
index b3758cc..7886bab 100644
--- a/lib/wolff_tools.c
+++ b/lib/wolff_tools.c
@@ -2,6 +2,10 @@
#include "queue.h"
#include "wolff.h"
+int32_t sign(double x) {
+ return x > 0 ? 1 : -1;
+}
+
graph_t *graph_add_ext(const graph_t *g) {
graph_t *h = (graph_t *)calloc(1, sizeof(graph_t));
@@ -131,8 +135,8 @@ uint32_t wolff_step(double T, double H, ising_state_t *s, gsl_rng *r,
cluster_t *c = flip_cluster(s->g, ps, s->spins, r);
- s->M += -2 * c->dHb;
- s->H += 2 * (c->dJb + H * c->dHb);
+ s->M += - sign(H) * 2 * c->dHb;
+ s->H += 2 * (c->dJb + sign (H) * H * c->dHb);
uint32_t n_flips = c->nv;