From b5998a15cdbab21f03a65d9885dbde39615dc087 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Fri, 20 Jul 2018 23:21:39 -0400
Subject: cos and sin calls for computing fourier term now precomputed

---
 lib/cluster.h | 35 ++++++-----------------------------
 lib/state.h   | 11 +++++++++++
 2 files changed, 17 insertions(+), 29 deletions(-)

diff --git a/lib/cluster.h b/lib/cluster.h
index 4b3c2f6..d90dc64 100644
--- a/lib/cluster.h
+++ b/lib/cluster.h
@@ -29,30 +29,6 @@
 #include "dihinf.h"
 #include "yule_walker.h"
 
-template <class T>
-void init(T*);
-
-template <class T>
-T scalar_multiple(v_t a, T b);
-
-template <class R_t, class X_t>
-X_t act(R_t a, X_t b);
-
-template <class R_t, class X_t>
-X_t act_inverse(R_t a, X_t b);
-
-template <class T>
-T copy(T a);
-
-template <class T>
-void free_spin(T a);
-
-template <class T>
-T add(T, T);
-
-template <class T>
-T subtract(T, T);
-
 template <class R_t, class X_t>
 void flip_cluster(state_t <R_t, X_t> *state, v_t v0, R_t r, gsl_rng *rand) {
   v_t nv = 0;
@@ -114,12 +90,13 @@ void flip_cluster(state_t <R_t, X_t> *state, v_t v0, R_t r, gsl_rng *rand) {
           state->E += dE;
 
           for (D_t i = 0; i < state->D; i++) {
-            double x = (double)((non_ghost / (v_t)pow(state->L, state->D - i - 1)) % state->L) / (double)state->L; 
-            add(&(state->ReF[i]), -cos(2 * M_PI * x), rs_old);
-            add(&(state->ReF[i]),  cos(2 * M_PI * x), rs_new);
+            L_t x = (non_ghost / (v_t)pow(state->L, state->D - i - 1)) % state->L;
+
+            add(&(state->ReF[i]), -state->precomputed_cos[i], rs_old);
+            add(&(state->ReF[i]),  state->precomputed_cos[i], rs_new);
 
-            add(&(state->ImF[i]), -sin(2 * M_PI * x), rs_old);
-            add(&(state->ImF[i]),  sin(2 * M_PI * x), rs_new);
+            add(&(state->ImF[i]), -state->precomputed_sin[i], rs_old);
+            add(&(state->ImF[i]),  state->precomputed_sin[i], rs_new);
           }
 
           free_spin (rs_old);
diff --git a/lib/state.h b/lib/state.h
index b40b85c..76d3e5a 100644
--- a/lib/state.h
+++ b/lib/state.h
@@ -23,6 +23,9 @@ class state_t {
     v_t last_cluster_size;
     typename X_t::F_t *ReF;
     typename X_t::F_t *ImF;
+    // updating fourier terms F requires many cos and sin calls, faster to do it beforehand.
+    double *precomputed_cos;
+    double *precomputed_sin;
 
     std::function <double(X_t, X_t)> J;
     std::function <double(X_t)> H;
@@ -47,6 +50,12 @@ class state_t {
         ReF[i] = scalar_multiple(0, spins[0]);
         ImF[i] = scalar_multiple(0, spins[0]);
       }
+      precomputed_cos = (double *)malloc(L * sizeof(double));
+      precomputed_sin = (double *)malloc(L * sizeof(double));
+      for (L_t i = 0; i < L; i++) {
+        precomputed_cos[i] = cos(2 * M_PI * (double)i / (double)L);
+        precomputed_sin[i] = sin(2 * M_PI * (double)i / (double)L);
+      }
     }
 
     ~state_t() {
@@ -63,6 +72,8 @@ class state_t {
       }
       free(ReF);
       free(ImF);
+      free(precomputed_sin);
+      free(precomputed_cos);
     }
 };
 
-- 
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