From 639552a2649139ba14363f30daa20786532b21b0 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Mon, 23 Jul 2018 13:51:13 -0400
Subject: implemented the discrete gaussian model for roughening

---
 src/wolff_potts.cpp | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

(limited to 'src/wolff_potts.cpp')

diff --git a/src/wolff_potts.cpp b/src/wolff_potts.cpp
index 3b55472..74e0ea9 100644
--- a/src/wolff_potts.cpp
+++ b/src/wolff_potts.cpp
@@ -90,21 +90,21 @@ int main(int argc, char *argv[]) {
   state_t <symmetric_t<POTTSQ>, potts_t<POTTSQ>> s(D, L, T, Z, B);
 
   // define function that generates self-inverse rotations
-  std::function <symmetric_t<POTTSQ>(gsl_rng *, const sim_t *)> gen_R = [] (gsl_rng *r, const sim_t *s) -> symmetric_t<POTTSQ> {
+  std::function <symmetric_t<POTTSQ>(gsl_rng *, potts_t<POTTSQ>)> gen_R = [] (gsl_rng *r, potts_t<POTTSQ> v) -> symmetric_t<POTTSQ> {
     symmetric_t<POTTSQ> rot;
     init(&rot);
 
-    for (int i = POTTSQ - 1; i >= 0; i--) {
-      if (rot.perm[i] == i) {
-        q_t j = gsl_rng_uniform_int(r, i + 1);
-        if (rot.perm[j] == j) {
-          q_t tmp = rot.perm[i];
-          rot.perm[i] = rot.perm[j];
-          rot.perm[j] = tmp;
-        }
-      }
+    q_t j = gsl_rng_uniform_int(r, POTTSQ - 1);
+    q_t swap_v;
+    if (j < v.x) {
+      swap_v = j;
+    } else {
+      swap_v = j + 1;
     }
 
+    rot.perm[v.x] = swap_v;
+    rot.perm[swap_v] = v.x;
+
     return rot;
   };
 
-- 
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