From 59100a471f90b46023741c16fffb69f72e6b8edd Mon Sep 17 00:00:00 2001
From: Ian Jauslin <ian.jauslin@rutgers.edu>
Date: Wed, 12 Apr 2023 14:37:02 -0400
Subject: Running average

---
 src/navier-stokes.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 107 insertions(+), 5 deletions(-)

(limited to 'src/navier-stokes.c')

diff --git a/src/navier-stokes.c b/src/navier-stokes.c
index 19e2f69..5d71d73 100644
--- a/src/navier-stokes.c
+++ b/src/navier-stokes.c
@@ -90,6 +90,7 @@ int eea(
   _Complex double* g,
   bool irreversible,
   unsigned int print_freq,
+  unsigned int running_avg_window,
   unsigned int starting_time,
   unsigned int nthreads,
   FILE* savefile
@@ -100,6 +101,11 @@ int eea(
   _Complex double* tmp3;
   double alpha, energy, enstrophy;
   double avg_e,avg_a,avg_en;
+  // quantities needed to compute averages
+  double *save_print_e, *save_print_a, *save_print_en;
+  double *save_print_short_e, *save_print_short_a, *save_print_short_en;
+  // index
+  unsigned int i;
   unsigned int t;
   fft_vect fft1;
   fft_vect fft2;
@@ -115,6 +121,28 @@ int eea(
   avg_a=0;
   avg_en=0;
 
+  // need this for running average
+  unsigned int short_len=running_avg_window % print_freq;
+  // number of full print intervals in running average window
+  unsigned int nr_print_in_window = (running_avg_window-short_len)/print_freq;
+  double avg_print_e=0;
+  double avg_print_a=0;
+  double avg_print_en=0;
+  double avg_print_short_e=0;
+  double avg_print_short_a=0;
+  double avg_print_short_en=0;
+
+  // save e a en for running average
+  // only need to save if window is non zero
+  if(running_avg_window!=0){
+    save_print_e=calloc(sizeof(double), nr_print_in_window);
+    save_print_a=calloc(sizeof(double), nr_print_in_window);
+    save_print_en=calloc(sizeof(double), nr_print_in_window);
+    save_print_short_e=calloc(sizeof(double), nr_print_in_window+1);
+    save_print_short_a=calloc(sizeof(double), nr_print_in_window+1);
+    save_print_short_en=calloc(sizeof(double), nr_print_in_window+1);
+  }
+
   // iterate
   for(t=starting_time;t<starting_time+nsteps;t++){
     ns_step(u, K1, K2, N1, N2, nu, delta, L, g, fft1, fft2, ifft, tmp1, tmp2, tmp3, irreversible);
@@ -127,18 +155,92 @@ int eea(
     enstrophy=compute_enstrophy(u, K1, K2, L);
     
     // running average
-    if(t>0){
-      avg_e=avg_e-(avg_e-energy)/t;
-      avg_a=avg_a-(avg_a-alpha)/t;
-      avg_en=avg_en-(avg_en-enstrophy)/t;
+    // if window=0, then take average over all times
+    if(running_avg_window==0){
+      if(t!=0){
+	avg_e=avg_e-(avg_e-energy)/t;
+	avg_a=avg_a-(avg_a-alpha)/t;
+	avg_en=avg_en-(avg_en-enstrophy)/t;
+      }
+    }
+    else{
+      // reset print interval averages
+      if(t % print_freq == 1){
+	avg_print_e=0;
+	avg_print_a=0;
+	avg_print_en=0;
+	avg_print_short_e=0;
+	avg_print_short_a=0;
+	avg_print_short_en=0;
+      }
+
+      // compute average over print interval
+      avg_print_e=avg_print_e+energy/print_freq;
+      avg_print_a=avg_print_a+alpha/print_freq;
+      avg_print_en=avg_print_en+enstrophy/print_freq;
+
+      // compute average over the last short_len elements of a print interval
+      if (short_len != 0 && (t % print_freq > print_freq-short_len || t % print_freq == 0)){
+	avg_print_short_e+=energy/short_len;
+	avg_print_short_a+=alpha/short_len;
+	avg_print_short_en+=enstrophy/short_len;
+      }
+
+      if(t % print_freq ==0 && t>0){
+	// compute averages
+	if (t > running_avg_window) {
+	  avg_e=save_print_short_e[nr_print_in_window]*((double)short_len/running_avg_window);
+	  avg_a=save_print_short_a[nr_print_in_window]*((double)short_len/running_avg_window);
+	  avg_en=save_print_short_en[nr_print_in_window]*((double)short_len/running_avg_window);
+	  for(i=0;i<nr_print_in_window;i++){
+	    // prevent warnings: these will be initialized as long as t > running_avg_window
+	    #pragma GCC diagnostic push
+	    #pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+	    avg_e+=save_print_e[i]*((double)print_freq/running_avg_window);
+	    avg_a+=save_print_a[i]*((double)print_freq/running_avg_window);
+	    avg_en+=save_print_en[i]*((double)print_freq/running_avg_window);
+	    #pragma GCC diagnostic pop
+	  }
+	}
+
+	// memorize averages for future use
+	// need to keep track of case ==0, otherwise nr_print_in_window-1 is not an unsigned int
+	if(nr_print_in_window>0){
+	  for(i=0;i<nr_print_in_window-1;i++){
+	    save_print_e[i+1]=save_print_e[i];
+	    save_print_a[i+1]=save_print_a[i];
+	    save_print_en[i+1]=save_print_en[i];
+	  }
+	}
+	for(i=0;i<nr_print_in_window;i++){
+	  save_print_short_e[i+1]=save_print_short_e[i];
+	  save_print_short_a[i+1]=save_print_short_a[i];
+	  save_print_short_en[i+1]=save_print_short_en[i];
+	}
+	save_print_e[0]=avg_print_e;
+	save_print_a[0]=avg_print_a;
+	save_print_en[0]=avg_print_en;
+	save_print_short_e[0]=avg_print_short_e;
+	save_print_short_a[0]=avg_print_short_a;
+	save_print_short_en[0]=avg_print_short_en;
+      }
     }
 
-    if(t>0 && t%print_freq==0){
+    if(t>running_avg_window && t%print_freq==0){
       fprintf(stderr,"%d % .8e % .8e % .8e % .8e % .8e % .8e % .8e\n",t,t*delta, avg_a, avg_e, avg_en, alpha, energy, enstrophy);
       printf("%8d % .15e % .15e % .15e % .15e % .15e % .15e % .15e\n",t,t*delta, avg_a, avg_e, avg_en, alpha, energy, enstrophy);
     }
   }
 
+  if(running_avg_window!=0){
+    free(save_print_e);
+    free(save_print_a);
+    free(save_print_en);
+    free(save_print_short_e);
+    free(save_print_short_a);
+    free(save_print_short_en);
+  }
+
   // save final entry to savefile
   write_u(u, K1, K2, savefile);
 
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